Patent Publication Number: US-11392221-B2

Title: Touch sensitive processing apparatus, system and operating method thereof for receiving electrical signals carrying pressure information

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part application claims benefits of a U.S. patent application Ser. No. 15/184,286 and a U.S. patent application Ser. No. 15,788,051, filed on Oct. 19, 2017, which is a continuation application of U.S. patent application Ser. No. 14/537,082, filed on Nov. 10, 2014 and issued as U.S. Pat. No. 9,851,816, which claims priorities under 35 U.S.C. 119 to U.S. provisional patent application, 61/902,137, filed on Nov. 8, 2013, U.S. provisional patent application, 61/945,397, filed on Feb. 27, 2014, U.S. provisional patent application, 61/992,340, filed on May 13, 2014, and U.S. provisional patent application, 62/055,995, filed on Sep. 26, 2014. The U.S. patent Ser. No. 15/184,286 is filed on Jun. 16, 2016, which claims priority to a U.S. provisional patent application No. 62/180,272, filed on Jun. 16, 2015 and a Taiwan patent application No. 104144644, filed on Dec. 31, 2015, the disclosures of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to transmitter, and more particularly, to transmitter which is able to transmit an electric signal precisely representing a pressure on the transmitter. 
     2. Description of the Prior Art 
     Touch panel or touch sensitive screen is important human machine interface in modern age. In addition to detecting approximation or touch of human body, touch panel is also used for detecting approximation or touch of stylus or tip of stylus such that user is able to precisely control a trace painted by a touching tip. 
     Stylus may actively emit electrical signals via its tip. In this present application, it is called active stylus. When the tip approximating or touching a touch panel, electromagnetic response of the electric signal occurs to electrodes of the touch panel. By detecting the electromagnetic response corresponding to the electric signal, the stylus approximating or touching the sensing electrodes could be detected. Therefore a position of the tip relative to the touch panel could be concluded accordingly. 
     Hence, it is required to have active stylus transmitting electrical signals which precisely reflect the pressure level. 
     From the above it is clear that prior art still has shortcomings. In order to solve these problems, efforts have long been made in vain, while ordinary products and methods offering no appropriate structures and methods. Thus, there is a need in the industry for a novel technique that solves these problems. 
     SUMMARY OF THE INVENTION 
     One object of the present invention is to provide a stylus which is able to transmit electric signals precisely representing a pressure on the stylus. 
     One object of the present invention is to provide a stylus for transmitting electrical signals carrying pressure information, comprising: a first component with variable impedance reflecting a pressure, wherein the first component is configured for receiving first signals encoded by a first pseudo-random number (PN) code; a second component with fixed impedance, wherein the second component is configured for receiving second signals encoded by a second PN code; and a conductive tip section configured for: receiving, simultaneously, the first signals from the first component and the second signals from the second component; and transmitting electrical signals which is composed of the first signals and the second signals, wherein the first PN code is orthogonal to the second PN code. 
     In one embodiment, in order to provide the first PN code and the second PN code onboard the stylus, the stylus further comprises a controller, configured for: generating the first signals according to the first PN code; generating the second signals according the second PN code; transmitting the first signals to the first component; and transmitting the second signals to the second component. 
     In one embodiment, in order to transmit status of onboard sensor of the stylus, the stylus further comprises: at least one onboard sensor coupled to the controller. The controller is further configured for: generating data codes according to status of the at least one onboard sensor; generating first data codes according to the data codes and the first PN code; and transmitting the first data codes to the first component. The first component is further configured for receiving the first data codes from the controller. The conductive tip section is further configured for: receiving the first data codes from the first component; and transmitting the first data codes. 
     In one embodiment, in order to transmit status of onboard sensor of the stylus, the stylus further comprises: at least one onboard sensor coupled to the controller. The controller is further configured for: generating data codes according to status of the at least one onboard sensor; generating second data codes according to the data codes and the second PN code; and transmitting the second data codes to the second component. The second component is further configured for receiving the second data codes from the controller. The conductive tip section is further configured for: receiving the second data codes from the second component; and transmitting the second data codes. 
     In one embodiment, in order to synchronize with receiving procedure of a touch sensitive processing apparatus of a touch panel, the controller is further configured for: receiving a synchronization signal from an electronic device; and after the synchronization signal is received, executing the generating steps and the transmitting steps. 
     In one embodiment, in order to synchronize with receiving procedure of the touch sensitive processing apparatus of the touch panel where the stylus touches or approximates, the controller is coupled to the conductive tip section for receiving the synchronization signal which is being transmitted from electrodes of a touch panel of the electronic device. 
     In one embodiment, in order to prevent conflicts of PN codes when multiple styli operate with one touch panel, the stylus further comprises a human-machine interface for user&#39;s input of PN codes, wherein the controller is further configured for receiving a setting instruction from the human-machine interface for designating a set of the first PN code and the second PN code. 
     In one embodiment, in order to provide PN code setting information to user, the stylus further comprises at least one of following device coupled to the controller for indicating a set of the first PN code and the second PN code: a visual indicator; and an audio indicator. 
     In one embodiment, in order to provide a wire connection between the corded or tethered stylus and a touch sensitive processing apparatus, the stylus further comprises: a first signal circuit, coupled to the first component and a touch sensitive processing apparatus, configured for propagating the first signals from the touch sensitive processing apparatus to the first component; and a second signal circuit, coupled to the second component and the touch sensitive processing apparatus, configured for propagating the second signals from the touch sensitive processing apparatus to the second component. 
     In one embodiment, in order to provide a switch status to a touch sensitive processing apparatus, the stylus further comprises a third switch configured for receiving the first signals; and a third component with fixed impedance, coupled to the third switch and the conductive tip section, wherein the third switch is selectively being opened or closed, the first signals are propagated through the third switch and the third component to the conductive tip section when the third switch is being closed. 
     In one embodiment, in order to provide a switch status to a touch sensitive processing apparatus, the stylus further comprises a fourth switch configured for receiving the second signals; and a fourth component with fixed impedance, coupled to the fourth switch and the conductive tip section, wherein the fourth switch is selectively being opened or closed, the second signals are propagated through the fourth switch and the fourth component to the conductive tip section when the fourth switch is being closed. 
     One object of the present invention is to provide a method for transmitting electrical signals carrying pressure information from a stylus, comprising: receiving, by a first component with variable impedance reflecting a pressure, first signals encoded by a first PN code; receiving, by a second component with fixed impedance, second signals encoded by a second PN code; receiving, simultaneously, the first signals from the first component and the second signals from the second component by a conductive tip section; and transmitting electrical signals which is composed of the first signals and the second signals by the conductive tip section, wherein the first PN code is orthogonal to the second PN code. 
     In one embodiment, in order to provide the first PN code and the second PN code onboard the stylus, the method further comprises: generating the first signals according to the first PN code; generating the second signals according the second PN code; transmitting the first signals to the first component; and transmitting the second signals to the second component. 
     In one embodiment, in order to transmit status of onboard sensor of the stylus, the method further comprises: generating data codes according to status of at least one onboard sensor; generating first data codes according to the data codes and the first PN code; transmitting the first data codes to the first component; transmitting, by the first component, the first data codes to the conductive tip section; and transmitting, by the conductive tip section, the first data codes. 
     In one embodiment, in order to transmit status of onboard sensor of the stylus, the method further comprises: generating data codes according to status of at least one onboard sensor; generating second data codes according to the data codes and the second PN code; transmitting the second data codes to the second component; transmitting, by the second component, the second data codes to the conductive tip section; and transmitting, by the conductive tip section, the first data codes. 
     In one embodiment, in order to synchronize with receiving procedure of a touch sensitive processing apparatus of a touch panel, the method is further configured for: receiving a synchronization signal from an electronic device; and after the synchronization signal is received, executing the generating steps and the transmitting steps. 
     In one embodiment, in order to synchronize with receiving procedure of the touch sensitive processing apparatus of the touch panel where the stylus touches or approximates, the synchronization signal which is being transmitted from electrodes of a touch panel of the electronic device to the conductive tip section. 
     In one embodiment, in order to prevent conflicts of PN codes when multiple styli operate with one touch panel, the method further comprises: receiving a setting instruction from a human-machine interface of the stylus for designating a set of the first PN code and the second PN code. 
     In one embodiment, in order to provide PN code setting information to user, the method further comprises at least one of following steps: having a visual indicator of the stylus indicating a set of the first PN code and the second PN code; and having an audio indicator of the stylus indicating the set of the first PN code and the second PN code. 
     In one embodiment, in order to provide a wire connection between the corded or tethered stylus and a touch sensitive processing apparatus, the method further comprises: receiving, by a first signal circuit, the first signals from a touch sensitive processing apparatus; propagating, by the first signal circuit, the first signals to the first component; receiving, by a second signal circuit, the second signals from the touch sensitive processing apparatus; and propagating, by the second signal circuit, the second signals to the second component. 
     In one embodiment, in order to provide a switch status to a touch sensitive processing apparatus, the method further comprises: selectively receiving, by a third component with fixed impedance, the first signals; and selectively transmitting, by the third component, the first signals to the conductive tip section. 
     In one embodiment, in order to provide a switch status to a touch sensitive processing apparatus, the method further comprises: selectively receiving, by a fourth component with fixed impedance, the second signals; and selectively transmitting, by the fourth component, the second signals to the conductive tip section. 
     One object of the present invention is to provide a touch sensitive processing apparatus for receiving electrical signals carrying pressure information transmitted from a first stylus, comprising: a sensing circuit, configured for receiving the electrical signals via electrodes of a touch panel; and a processor, coupled to the sensing circuit, configured for: despreading a first preamble code of the received electrical signals in accordance with a first pseudo-random number (PN) code; despreading a second preamble code of the received electrical signals in accordance with a second PN code; and calculating the pressure information according to a first signal strength ratio of a first part of the received electrical signal and a second part of the received electrical signal, wherein the first part comprises the first preamble code and the second part comprises the second preamble code, wherein the first PN code is orthogonal to the second PN code. 
     In one embodiment, in order to trigger the stylus for transmitting electrical signals synchronously, the touch sensitive processing apparatus further comprises a driving circuit, coupled to the electrodes of the touch panel, wherein the processor is further configured for having the driving circuit to transmit a beacon signal via the electrodes of the touch panel before the receiving step is being executed. 
     In one embodiment, in order to receive status of sensor onboard the stylus, the processor is further configured for: decoding first data codes of the received electrical signal in accordance with the first PN code, wherein the first data codes represents status of at least one onboard sensor of the first stylus. 
     In one embodiment, in order to receive status of sensor onboard the stylus, the processor is further configured for: decoding second data codes of the received electrical signal in accordance with the second PN code, wherein the second data codes represents status of at least one onboard sensor of the first stylus. 
     In one embodiment, in order to correctly receive status of sensor onboard the stylus, the processor is further configured for: decoding first data codes of the received electrical signal in accordance with the first PN code; decoding second data codes of the received electrical signal in accordance with the second PN code; and determining data codes if the first data codes and the second data codes are the same, wherein the data codes represents status of at least one onboard sensor of the first stylus. 
     In one embodiment, in order to receive more smooth and averaged pressure information in a longer transmission, the first part further comprises the first data codes and the second part further comprises the second data codes. 
     In one embodiment, in order to synchronize with the transmission of the stylus more quickly, the processor is further configured for: coupling at least two of second electrodes of the touch panel as a synchronization channel, wherein the despreading steps of the first preamble code and the second preamble code are being executed on the received electrical signals of the synchronization channel to retrieve a first synchronization information and a second synchronization information, respectively, wherein the second electrodes are arranged in parallel to each other. 
     In one embodiment, in order to correctly and quickly receive status of sensor onboard the stylus by utilizing synchronization information, the processor is further configured for: decoding first data codes of the received electrical signal from at least one of first electrodes of the touch panel in accordance with the first PN code and the first synchronization information; decoding second data codes of the received electrical signal from at least one of the first electrodes of the touch panel in accordance with the second PN code and the second synchronization information; and determining data codes if the first data codes and the second data codes are the same, wherein the data codes represents status of at least one onboard sensor of the first stylus, wherein the first electrodes are arranged in parallel to each other, and the first electrodes intersect with the second electrodes. 
     In one embodiment, in order to concurrently receive electrical signals from multiple styli, the processor is further configured for: despreading a third preamble code of the received electrical signals in accordance with a third PN code; despreading a fourth preamble code of the received electrical signals in accordance with a fourth PN code; and calculating a pressure information of a second stylus according to a second signal strength ratio of a third part of the received electrical signal and a fourth part of the received electrical signal, wherein the third part comprises the third preamble code and the fourth part comprises the fourth preamble code, wherein the first PN code, the second PN code, the third PN code and the fourth PN code are orthogonal to each other. 
     In one embodiment, in order to provide a wire connection between a corded or tethered stylus and the touch sensitive processing apparatus, the touch sensitive processing apparatus further comprises: a stylus interface, coupled to a first signal circuit and a second signal circuit of the first stylus, wherein the processor, coupled to the stylus interface, is further configured for: generating the first preamble code in accordance with the first PN code; generating the second preamble code in accordance with the second PN code; and transmitting the first preamble code and the second preamble code to the first signal circuit and the second signal circuit via the stylus interface, respectively. 
     In one embodiment, in order to receive status of a switch of the stylus, the processor is further configured for: calculating a switch status of the first stylus according to the first signal strength ratio of the first part of the received electrical signal and the second part of the received electrical signal. 
     In one embodiment, in order to concurrently connect with multiple corded or tethered styli, the stylus interface is further coupled to a third signal circuit and a fourth signal circuit of a second stylus. The processor, coupled to the stylus interface, is further configured for: generating a third preamble code in accordance with a third PN code; generating a fourth preamble code in accordance with a fourth PN code; and transmitting the third preamble code and the fourth preamble code to the third signal circuit and the fourth signal circuit via the stylus interface, respectively, wherein the first PN code, the second PN code, the third PN code and the fourth PN code are orthogonal to each other. 
     One object of the present invention is to provide a method for receiving electrical signals carrying pressure information transmitted from a first stylus, comprising: receiving the electrical signals via electrodes of a touch panel; despreading a first preamble code of the received electrical signals in accordance with a first PN code; despreading a second preamble code of the received electrical signals in accordance with a second PN code; and calculating the pressure information according to a first signal strength ratio of a first part of the received electrical signal and a second part of the received electrical signal, wherein the first part comprises the first preamble code and the second part comprises the second preamble code, wherein the first PN code is orthogonal to the second PN code. 
     In one embodiment, in order to trigger the stylus for transmitting electrical signals synchronously, the method further comprises: transmitting a beacon signal via the electrodes of the touch panel before the receiving step is being executed. 
     In one embodiment, in order to receive status of sensor onboard the stylus, the method further comprises: decoding first data codes of the received electrical signal in accordance with the first PN code, wherein the first data codes represents status of at least one onboard sensor of the first stylus. 
     In one embodiment, in order to receive status of sensor onboard the stylus, the method further comprises: decoding second data codes of the received electrical signal in accordance with the second PN code, wherein the second data codes represents status of at least one onboard sensor of the first stylus. 
     In one embodiment, in order to correctly receive status of sensor onboard the stylus, the method further comprises: decoding first data codes of the received electrical signal in accordance with the first PN code; decoding second data codes of the received electrical signal in accordance with the second PN code; and determining data codes if the first data codes and the second data codes are the same, wherein the data codes represents status of at least one onboard sensor of the first stylus. 
     In one embodiment, in order to receive more smooth and averaged pressure information in a longer transmission, the first part further comprises the first data codes and the second part further comprises the second data codes. 
     In one embodiment, in order to synchronize with the transmission of the stylus more quickly, the method further comprises: coupling at least two of second electrodes of the touch panel as a synchronization channel, wherein the despreading steps of the first preamble code and the second preamble code are being executed on the received electrical signals of the synchronization channel to retrieve a first synchronization information and a second synchronization information, respectively, wherein the second electrodes are arranged in parallel to each other. 
     In one embodiment, in order to correctly and quickly receive status of sensor onboard the stylus by utilizing synchronization information, the method further comprises: decoding first data codes of the received electrical signal from at least one of first electrodes of the touch panel in accordance with the first PN code and the first synchronization information; decoding second data codes of the received electrical signal from at least one of the first electrodes of the touch panel in accordance with the second PN code and the second synchronization information; and determining data codes if the first data codes and the second data codes are the same, wherein the data codes represents status of at least one onboard sensor of the first stylus, wherein the first electrodes are arranged in parallel to each other, and the first electrodes intersect with the second electrodes. 
     In one embodiment, in order to concurrently receive electrical signals from multiple styli, the method further comprises: despreading a third preamble code of the received electrical signals in accordance with a third PN code; despreading a fourth preamble code of the received electrical signals in accordance with a fourth PN code; and calculating a pressure information of a second stylus according to a second signal strength ratio of a third part of the received electrical signal and a fourth part of the received electrical signal, wherein the third part comprises the third preamble code and the fourth part comprises the fourth preamble code, wherein the first PN code, the second PN code, the third PN code and the fourth PN code are orthogonal to each other. 
     In one embodiment, in order to provide a wire connection between a corded or tethered stylus and the touch sensitive processing apparatus, the method further comprises: generating the first preamble code in accordance with the first PN code; generating the second preamble code in accordance with the second PN code; and transmitting the first preamble code and the second preamble code to a first signal circuit and a second signal circuit of the first stylus, respectively. 
     In one embodiment, in order to receive status of a switch of the stylus, the method further comprises: calculating a switch status of the first stylus according to the first signal strength ratio of the first part of the received electrical signal and the second part of the received electrical signal. 
     In one embodiment, in order to concurrently connect with multiple corded or tethered styli, the method further comprises: generating a third preamble code in accordance with a third PN code; generating a fourth preamble code in accordance with a fourth PN code; and transmitting the third preamble code and the fourth preamble code to a third signal circuit and a fourth signal circuit of a second stylus, respectively, wherein the first PN code, the second PN code, the third PN code and the fourth PN code are orthogonal to each other. 
     One object of the present invention is to provide a touch system, which comprising: a touch panel; a first stylus; and a touch sensitive processing apparatus for receiving electrical signals carrying pressure information transmitted from the first stylus. The touch sensitive processing apparatus comprises: a sensing circuit, configured for receiving the electrical signals via electrodes of the touch panel; and a processor, coupled to the sensing circuit, configured for: despreading a first preamble code of the received electrical signals in accordance with a first PN code; despreading a second preamble code of the received electrical signals in accordance with a second PN code; and calculating the pressure information according to a first signal strength ratio of a first part of the received electrical signal and a second part of the received electrical signal, wherein the first part comprises the first preamble code and the second part comprises the second preamble code, wherein the first PN code is orthogonal to the second PN code. 
     In one embodiment, the first stylus further comprises: a first component with variable impedance reflecting a pressure, wherein the first component is configured for receiving first signals encoded by the first PN code; a second component with fixed impedance, wherein the second component is configured for receiving second signals encoded by the second PN code; and a conductive tip section configured for: receiving, simultaneously, the first signals from the first component and the second signals from the second component; and transmitting the electrical signals which is composed of the first signals and the second signals. 
     One object of the present invention is to provide a stylus for transmitting electrical signals carrying pressure information, comprising: a first component with variable impedance reflecting a pressure, wherein the first component is configured for receiving first signals encoded by a pseudo-random number (PN) code in a first time period; a second component with fixed impedance, wherein the second component is configured for receiving second signals encoded by the PN code in a second time period; and a conductive tip section configured for: receiving the first signals from the first component in the first time period; receiving the second signals from the second component in the second time period; transmitting electrical signals which is composed of the first signals in the first time period; and transmitting electrical signals which is composed of the second signals in the second time period. 
     In one embodiment, in order to provide the PN code onboard the stylus, the stylus further comprises a controller, configured for: generating the first signals according to the PN code; generating the second signals according the PN code; transmitting the first signals to the first component; and transmitting the second signals to the second component. 
     In one embodiment, in order to transmit status of onboard sensor of the stylus, the stylus further comprises: at least one onboard sensor coupled to the controller, wherein the controller is further configured for: generating data codes according to status of the at least one onboard sensor; generating first data codes according to the data codes and the PN code; and transmitting the first data codes to the first component. The first component is further configured for receiving the first data codes from the controller in the first time period. The conductive tip section is further configured for in the first time period: receiving the first data codes from the first component; and transmitting the first data codes. 
     In one embodiment, in order to transmit status of onboard sensor of the stylus, the stylus further comprises: at least one onboard sensor coupled to the controller, wherein the controller is further configured for: generating data codes according to status of the at least one onboard sensor; generating second data codes according to the data codes and the PN code; and transmitting the second data codes to the second component. The second component is further configured for receiving the second data codes from the controller in the second time period. The conductive tip section is further configured for in the second time period: receiving the second data codes from the second component; and transmitting the second data codes. 
     In one embodiment, in order to synchronize with receiving procedure of a touch sensitive processing apparatus of a touch panel, the controller is further configured for: receiving a synchronization signal from an electronic device; and after the synchronization signal is received, executing the generating steps and the transmitting steps. 
     In one embodiment, in order to synchronize with receiving procedure of the touch sensitive processing apparatus of the touch panel where the stylus touches or approximates, the controller is coupled to the conductive tip section for receiving the synchronization signal which is being transmitted from electrodes of a touch panel of the electronic device. 
     In one embodiment, in order to prevent conflicts of PN codes when multiple styli operate with one touch panel, the stylus further comprises a human-machine interface for user&#39;s input of PN codes, wherein the controller is further configured for receiving a setting instruction from the human-machine interface for designating the PN code. 
     In one embodiment, in order to provide PN code setting information to user, the stylus further comprises at least one of following device coupled to the controller for indicating the PN code: a visual indicator; and an audio indicator. 
     In one embodiment, in order to provide a wire connection between the corded or tethered stylus and a touch sensitive processing apparatus, the stylus further comprises: a first signal circuit, coupled to the first component and a touch sensitive processing apparatus, configured for propagating the first signals from the touch sensitive processing apparatus to the first component; and a second signal circuit, coupled to the second component and the touch sensitive processing apparatus, configured for propagating the second signals from the touch sensitive processing apparatus to the second component. 
     In order to provide a switch status to a touch sensitive processing apparatus, the stylus further comprises: a fourth switch configured for receiving the second signals in the second time period; and a fourth component with fixed impedance, coupled to the fourth switch and the conductive tip section, wherein the fourth switch is selectively being opened or closed, the second signals are propagated through the fourth switch and the fourth component to the conductive tip section when the fourth switch is being closed. 
     In order to provide a switch status to a touch sensitive processing apparatus, the stylus further comprises: a fourth switch configured for receiving the second signals in the second time period; and a fourth component with fixed impedance, coupled to the third switch and the conductive tip section, wherein the fourth switch is selectively being opened or closed, the second signals are propagated through the fourth switch and the fourth component to the conductive tip section when the fourth switch is being closed. 
     One object of the present invention is to provide a method for transmitting electrical signals carrying pressure information from a stylus, comprising: receiving, by a first component with variable impedance reflecting a pressure, first signals encoded by a PN code in a first time period; receiving, by a second component with fixed impedance, second signals encoded by the PN code in a second time period; receiving the first signals from the first component by a conductive tip section in the first time period; receiving the second signals from the second component by the conductive tip section in the second time period; and transmitting electrical signals which is composed of the first signals in the first time period by the conductive tip section; and transmitting electrical signals which is composed of the second signals in the second time period by the conductive tip section. 
     In one embodiment, in order to provide the PN code onboard the stylus, the method further comprises: generating the first signals according to the PN code; generating the second signals according the PN code; transmitting the first signals to the first component; and transmitting the second signals to the second component. 
     In one embodiment, in order to transmit status of onboard sensor of the stylus, the method further comprises: generating data codes according to status of at least one onboard sensor; generating first data codes according to the data codes and the PN code; transmitting the first data codes to the first component; transmitting, by the first component, the first data codes to the conductive tip section; and transmitting, by the conductive tip section, the first data codes. 
     In one embodiment, in order to transmit status of onboard sensor of the stylus, the method further comprises: generating data codes according to status of at least one onboard sensor; generating second data codes according to the data codes and the PN code; and transmitting the second data codes to the second component; transmitting, by the second component, the second data codes to the conductive tip section; and transmitting, by the conductive tip section, the second data codes. 
     In one embodiment, in order to synchronize with receiving procedure of a touch sensitive processing apparatus of a touch panel, the method further comprises: receiving a synchronization signal from an electronic device; and after the synchronization signal is received, executing the generating steps and the transmitting steps. 
     In one embodiment, in order to synchronize with receiving procedure of the touch sensitive processing apparatus of the touch panel where the stylus touches or approximates, wherein the synchronization signal which is being transmitted from electrodes of a touch panel of the electronic device to the conductive tip section. 
     In one embodiment, in order to prevent conflicts of PN codes when multiple styli operate with one touch panel, the method further comprises: receiving a setting instruction from a human-machine interface of the stylus for designating the PN code. 
     In one embodiment, in order to provide PN code setting information to user, the method further comprises at least one of following steps: having a visual indicator of the stylus indicating the PN code; and having an audio indicator of the stylus indicating the PN code. 
     In one embodiment, in order to provide a wire connection between the corded or tethered stylus and a touch sensitive processing apparatus, the method further comprises: receiving, by a first signal circuit, the first signals from a touch sensitive processing apparatus; propagating, by the first signal circuit, the first signals to the first component; receiving, by a second signal circuit, the second signals from the touch sensitive processing apparatus; and propagating, by the second signal circuit, the second signals to the second component. 
     In one embodiment, in order to provide a switch status to a touch sensitive processing apparatus, the method further comprises: selectively receiving, by a third component with fixed impedance, the first signals; and selectively transmitting, by the third component, the first signals to the conductive tip section. 
     In one embodiment, in order to provide a switch status to a touch sensitive processing apparatus, the method further comprises: selectively receiving, by a fourth component with fixed impedance, the second signals; and selectively transmitting, by the fourth component, the second signals to the conductive tip section. 
     One object of the present invention is to provide a touch sensitive processing apparatus for receiving electrical signals carrying pressure information transmitted from a first stylus, comprising: a sensing circuit, configured for receiving the electrical signals via electrodes of a touch panel; and a processor, coupled to the sensing circuit, configured for: despreading a first preamble code of the received electrical signals in accordance with a pseudo-random number (PN) code in a first time period; despreading a second preamble code of the received electrical signals in accordance with the PN code in a second time period; and calculating the pressure information according to a first signal strength ratio of a first part of the received electrical signal and a second part of the received electrical signal, wherein the first part comprises the first preamble code and the second part comprises the second preamble code. 
     In one embodiment, in order to trigger the stylus for transmitting electrical signals synchronously, the touch sensitive apparatus further comprises: a driving circuit, coupled to the electrodes of the touch panel, wherein the processor is further configured for having the driving circuit to transmit a beacon signal via the electrodes of the touch panel before the receiving steps are being executed. 
     In one embodiment, in order to receive status of sensor onboard the stylus, the processor is further configured for: decoding first data codes of the electrical signal received in the first time period in accordance with the PN code, wherein the first data codes represents status of at least one onboard sensor of the first stylus. 
     In one embodiment, in order to receive status of sensor onboard the stylus, the processor is further configured for: decoding second data codes of the electrical signal received in the second time period in accordance with the PN code, wherein the second data codes represents status of at least one onboard sensor of the first stylus. 
     In one embodiment, in order to correctly receive status of sensor onboard the stylus, the processor is further configured for: decoding first data codes of the electrical signal received in the first time period in accordance with the PN code; decoding second data codes of the electrical signal received in the second time period in accordance with the PN code; and determining data codes if the first data codes and the second data codes are the same, wherein the data codes represents status of at least one onboard sensor of the first stylus. 
     In one embodiment, in order to receive more smooth and averaged pressure information in a longer transmission, the first part further comprises the first data codes and the second part further comprises the second data codes. 
     In one embodiment, in order to synchronize with the transmission of the stylus more quickly, the processor is further configured for: coupling at least two of second electrodes of the touch panel as a synchronization channel, wherein the despreading steps of the first preamble code and the second preamble code are being executed on the received electrical signals of the synchronization channel to retrieve a first synchronization information and a second synchronization information, respectively, wherein the second electrodes are arranged in parallel to each other. 
     In one embodiment, in order to correctly and quickly receive status of sensor onboard the stylus by utilizing synchronization information, the processor is further configured for: decoding first data codes of the received electrical signal from at least one of first electrodes of the touch panel in accordance with the PN code and the first synchronization information; decoding second data codes of the received electrical signal from at least one of the first electrodes of the touch panel in accordance with the PN code and the second synchronization information; and determining data codes if the first data codes and the second data codes are the same, wherein the data codes represents status of at least one onboard sensor of the first stylus, wherein the first electrodes are arranged in parallel to each other, and the first electrodes intersect with the second electrodes. 
     In one embodiment, in order to receive electrical signals from multiple styli, the processor is further configured for: despreading a third preamble code of the electrical signals received in a third time period in accordance with a second PN code; despreading a fourth preamble code of the electrical signals received in a fourth time period in accordance with the second PN code; and calculating a pressure information of a second stylus according to a second signal strength ratio of a third part of the received electrical signal and a fourth part of the received electrical signal, wherein the third part comprises the third preamble code and the fourth part comprises the fourth preamble code, wherein the PN code and the second PN code are orthogonal to each other, wherein part of the third time period is overlapped with part of the first time period or part of the second time period. 
     In one embodiment, in order to provide a wire connection between a corded or tethered stylus and the touch sensitive processing apparatus, the touch sensitive processing apparatus further comprises: a stylus interface, coupled to a first signal circuit and a second signal circuit of the first stylus, wherein the processor, coupled to the stylus interface, is further configured for: generating the first preamble code in accordance with the PN code; generating the second preamble code in accordance with the PN code; transmitting the first preamble code to the first signal circuit via the stylus interface in the first time period; and transmitting the second preamble code to the second signal circuit via the stylus interface in the second time period. 
     In one embodiment, in order to receive status of a switch of the stylus, the processor is further configured for: calculating a switch status of the first stylus according to the first signal strength ratio of the first part of the received electrical signal and the second part of the received electrical signal. 
     In one embodiment, in order to concurrently connect with multiple styli, the stylus interface is further coupled to a third signal circuit and a fourth signal circuit of a second stylus. The processor, coupled to the stylus interface, is further configured for: generating a third preamble code in accordance with a second PN code in a third time period; generating a fourth preamble code in accordance with the second PN code in a fourth time period; transmitting the third preamble code to the third signal circuit in the third time period via the stylus interface; and transmitting the fourth preamble code to the fourth signal circuit in the fourth time period via the stylus interface, respectively, wherein the PN code and the second PN code are orthogonal to each other, wherein part of the third time period is overlapped with part of the first time period or part of the second time period. 
     One object of the present invention is to provide a method for receiving electrical signals carrying pressure information transmitted from a first stylus, comprising: receiving the electrical signals via electrodes of a touch panel; despreading a first preamble code of the electrical signals received in a first time period in accordance with a PN code; despreading a second preamble code of the electrical signals received in a second time period in accordance with the PN code; and calculating the pressure information according to a first signal strength ratio of a first part of the received electrical signal and a second part of the received electrical signal, wherein the first part comprises the first preamble code and the second part comprises the second preamble code. 
     In one embodiment, in order to trigger the stylus for transmitting electrical signals synchronously, the method further comprises transmitting a beacon signal via the electrodes of the touch panel before the receiving step is being executed. 
     In one embodiment, in order to receive status of sensor onboard the stylus, the method further comprises: decoding first data codes of the electrical signal received in the first time period in accordance with the PN code, wherein the first data codes represents status of at least one onboard sensor of the first stylus. 
     In one embodiment, in order to receive status of sensor onboard the stylus, the method further comprises: decoding second data codes of the electrical signal received in the second time period in accordance with the PN code, wherein the second data codes represents status of at least one onboard sensor of the first stylus. 
     In one embodiment, in order to correctly receive status of sensor onboard the stylus, the method further comprises: decoding first data codes of the electrical signal received in the first time period in accordance with the PN code; decoding second data codes of the electrical signal received in the second time period in accordance with the PN code; and determining data codes if the first data codes and the second data codes are the same, wherein the data codes represents status of at least one onboard sensor of the first stylus. 
     In one embodiment, in order to receive more smooth and averaged pressure information in a longer transmission, the first part further comprises the first data codes and the second part further comprises the second data codes. 
     In one embodiment, in order to synchronize with the transmission of the stylus more quickly, the method further comprises: coupling at least two of second electrodes of the touch panel as a synchronization channel, wherein the despreading steps of the first preamble code and the second preamble code are being executed on the received electrical signals of the synchronization channel to retrieve a first synchronization information and a second synchronization information, respectively, wherein the second electrodes are arranged in parallel to each other. 
     In one embodiment, in order to correctly and quickly receive status of sensor onboard the stylus by utilizing synchronization information, the method further comprises: decoding first data codes of the received electrical signal from at least one of first electrodes of the touch panel in accordance with the PN code and the first synchronization information; decoding second data codes of the received electrical signal from at least one of the first electrodes of the touch panel in accordance with the PN code and the second synchronization information; and determining data codes if the first data codes and the second data codes are the same, wherein the data codes represents status of at least one onboard sensor of the first stylus, wherein the first electrodes are arranged in parallel to each other, and the first electrodes intersect with the second electrodes. 
     In one embodiment, in order to concurrently receive electrical signals from multiple styli, the method further comprises: despreading a third preamble code of the electrical signals received in a third time period in accordance with a second PN code; despreading a fourth preamble code of the electrical signals received in a fourth time period in accordance with the second PN code; and calculating a pressure information of a second stylus according to a second signal strength ratio of a third part of the received electrical signal and a fourth part of the received electrical signal, wherein the third part comprises the third preamble code and the fourth part comprises the fourth preamble code, wherein the PN code and the second PN code are orthogonal to each other, wherein part of the third time period is overlapped with part of the first time period or part of the second time period. 
     In one embodiment, in order to provide a wire connection between a corded or tethered stylus and the touch sensitive processing apparatus, the method further comprises: generating the first preamble code in accordance with the PN code in the first time period; generating the second preamble code in accordance with the PN code in the second time period; transmitting the first preamble code to a first signal circuit of the first stylus in the first time period; and transmitting the second preamble code to a second signal circuit of the first stylus in the second time period. 
     In one embodiment, in order to receive status of a switch of the stylus, the method further comprises: calculating a switch status of the first stylus according to the first signal strength ratio of the first part of the received electrical signal and the second part of the received electrical signal. 
     In one embodiment, in order to concurrently connect with multiple corded or tethered styli, the method further comprises: generating a third preamble code in accordance with a second PN code in a third time period; generating a fourth preamble code in accordance with the second PN code in a fourth time period; transmitting the third preamble code to a third signal circuit of a second stylus in the third time period; and transmitting the fourth preamble code to a fourth signal circuit of the second stylus in the fourth time period, wherein the PN code and the second PN code are orthogonal to each other, wherein part of the third time period is overlapped with part of the first time period or part of the second time period. 
     One object of the present invention is to provide a touch system comprising: a touch panel; a first stylus; and a touch sensitive processing apparatus. The touch sensitive processing apparatus for receiving electrical signals carrying pressure information transmitted from the first stylus, comprising: a sensing circuit, configured for receiving the electrical signals via electrodes of the touch panel; and a processor, coupled to the sensing circuit, configured for: despreading a first preamble code of the received electrical signals in accordance with a PN code in a first time period; despreading a second preamble code of the received electrical signals in accordance with the PN code in a second time period; and calculating the pressure information according to a first signal strength ratio of a first part of the received electrical signal and a second part of the received electrical signal, wherein the first part comprises the first preamble code and the second part comprises the second preamble code. 
     In one embodiment, the first stylus comprising: a first component with variable impedance reflecting a pressure, wherein the first component is configured for receiving first signals encoded by the PN code in the first time period; a second component with fixed impedance, wherein the second component is configured for receiving second signals encoded by the PN code in the second time period; and a conductive tip section configured for: receiving the first signals from the first component in the first time period; receiving the second signals from the second component in the second time period; transmitting electrical signals which is composed of the first signals in the first time period; and transmitting electrical signals which is composed of the second signals in the second time period. 
     The above description is only an outline of the technical schemes of the present invention. Preferred embodiments of the present invention are provided below in conjunction with the attached drawings to enable one with ordinary skill in the art to better understand said and other objectives, features and advantages of the present invention and to make the present invention accordingly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention can be more fully understood by reading the following detailed description of the preferred embodiments, with reference made to the accompanying drawings, wherein: 
         FIG. 1  illustrates a block diagram of a touch sensitive system  100  in accordance with an embodiment of the present invention. 
         FIG. 2  depicts a block diagram of a transmitter  110  in accordance with an embodiment of the present invention. 
         FIG. 3  shows a block diagram of a transmitter  110  in accordance with an embodiment of the present invention. 
         FIG. 4A  depicts a block diagram of a transmitter  110  in accordance with an embodiment of the present invention. 
         FIG. 4B  depicts a block diagram of a transmitter  110  in accordance with an embodiment of the present invention. 
         FIG. 5  depicts a block diagram of a transmitter  110  in accordance with an embodiment of the present invention. 
         FIG. 6  depicts a flow chart diagram of determining the sensing value of the tip of transmitter or active stylus performed by a processing apparatus in accordance with an embodiment of the present invention. 
         FIG. 7A  illustrates a block diagram of a transmitter  110  in accordance with an embodiment of the present invention. 
         FIG. 7B  illustrates a block diagram of a transmitter  110  in accordance with an embodiment of the present invention. 
         FIG. 7C  illustrates a block diagram of a transmitter  110  in accordance with an embodiment of the present invention. 
         FIG. 7D  illustrates a block diagram of a transmitter  110  in accordance with an embodiment of the present invention. 
         FIG. 8  shows a flow chart of determining a sensing value of the tip section of the transmitter in accordance with an embodiment of the present invention. 
         FIG. 9A  shows a timing sequence of signal modulation in accordance with an embodiment of the present invention. 
         FIG. 9B  shows a timing sequence of signal modulation in accordance with an embodiment of the present invention. 
         FIG. 9C  shows a timing sequence of signal modulation in accordance with an embodiment of the present invention. 
         FIG. 9D  shows a timing sequence of signal modulation in accordance with an embodiment of the present invention. 
         FIG. 9E  shows a timing sequence of signal modulation in accordance with an embodiment of the present invention. 
         FIG. 9F  shows a timing sequence of signal modulation in accordance with an embodiment of the present invention. 
         FIG. 10  shows noise propagation path in accordance with an embodiment of the present invention. 
         FIG. 11  depicts a structure diagram of a first capacitor  221  in accordance with an embodiment of the present invention. 
         FIG. 12  shows a diagram of reduced embodiment shown in  FIG. 11 . 
         FIG. 13  is a variation of the embodiment shown in  FIG. 12 . 
         FIG. 14  is a variation of the embodiment shown in  FIG. 13 . 
         FIG. 15  is a variation of the embodiment shown in  FIG. 14 . 
         FIG. 16A  shows a structure in accordance with an embodiment of the present invention. 
         FIG. 16B  is a variation of the embodiment shown in  FIG. 16A . 
         FIGS. 17A and 17B  show structural diagrams of the first capacitor and the second capacitor in accordance with an embodiment of the present invention. 
         FIG. 18  is a variation of the embodiment shown in  FIG. 11 . 
         FIG. 19A  depicts a profiling diagram of the FSC structure used in the transmitter  110  in accordance with an embodiment of the present invention. 
         FIG. 19B  shows an assembled profiling diagram of the structure shown in  FIG. 19A . 
         FIG. 19C  shows another assembled profiling diagram of the structure shown in  FIG. 19A . 
         FIG. 19D  depicts a profiling diagram of the FSC structure used in the transmitter  110  in accordance with an embodiment of the present invention. 
         FIG. 19E  depicts a profiling diagram of the FSC structure used in the transmitter  110  in accordance with an embodiment of the present invention. 
         FIG. 20  shows a profiling diagram of contact surface of the compressible conductor  1974  facing the dielectric film  1973 . 
         FIG. 21  illustrates a pressure sensor according to an embodiment of the present invention. 
         FIG. 22  illustrates a pressure sensor according to an embodiment of the present invention. 
         FIGS. 23A and 23B  depict profiling diagrams of a switch structure in accordance with an embodiment of the present invention. 
         FIGS. 24A and 24B  depict profiling diagrams of a switch structure in accordance with an embodiment of the present invention. 
         FIG. 25  shows a diagram for calculating the tip position. 
         FIG. 26  depicts a flow chart diagram for calculating the inclination angle in accordance with the present invention. 
         FIG. 27  shows embodiments of how display interface reflects strobe according to the inclination angle and/or pressure of the tip section. 
         FIG. 28  depicts other embodiments of how display interface reflects strobe according to the inclination angle and/or pressure of the tip. 
         FIG. 29  illustrates a block diagram of a system for detecting beacon signal in accordance with an embodiment of the present invention. 
         FIG. 30  depicts some waveforms of a spread spectrum technique. 
         FIG. 31  shows a variant of the embodiment as shown in  FIG. 1 . 
         FIG. 32  shows a flowchart of despreading method according to an embodiment of the present invention. 
         FIG. 33  depicts a diagram of an embodiment of an active stylus in accordance with the present invention. 
         FIG. 34  shows a block diagram of a touch sensitive processing apparatus  130  according to an embodiment of the present invention. 
         FIG. 35  illustrates a flowchart diagram practiced by the controller as shown in  FIG. 33  in accordance to an embodiment of the present invention. 
         FIG. 36A  illustrates a flowchart diagram practiced by the embedded processor in accordance to an embodiment of the present invention. 
         FIG. 36B  illustrates another flowchart diagram practiced by the embedded processor in accordance to an embodiment of the present invention. 
         FIG. 37A  illustrates a flowchart diagram practiced by the controller as shown in  FIG. 33  in accordance to an embodiment of the present invention. 
         FIG. 37B  illustrates another flowchart diagram practiced by the controller as shown in  FIG. 33  in accordance to an embodiment of the present invention. 
         FIG. 38A  illustrates a flowchart diagram practiced by the embedded processor in accordance to an embodiment of the present invention. 
         FIG. 38B  illustrates a flowchart diagram practiced by the embedded processor in accordance to an embodiment of the present invention. 
         FIG. 39A  illustrates a schematic diagram of a touch system in accordance with an embodiment of the present invention. 
         FIG. 39B  illustrates a schematic diagram of a variant of the touch system in accordance with an embodiment of the present invention. 
         FIG. 39C  illustrates a schematic diagram of a variant of the touch system in accordance with an embodiment of the present invention. 
         FIG. 40  depicts a schematic diagram of a touch sensitive processing apparatus in accordance with an embodiment of the invention. 
         FIG. 41A  illustrates a flowchart diagram of an operating method applicable to a corded stylus of an embodiment according to the invention. 
         FIG. 41B  illustrates a flowchart diagram of an operating method applicable to a corded stylus of an embodiment according to the invention. 
         FIG. 41C  illustrates a flowchart diagram of an operating method applicable to a corded stylus of an embodiment according to the invention 
         FIG. 42  depicts a flowchart diagram applicable to a touch sensitive processing apparatus according to an embodiment of the present invention. 
         FIG. 43  depicts a flowchart diagram applicable to a touch sensitive processing apparatus according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Some embodiments of the present invention are described in details below. However, in addition to the descriptions given below, the present invention can be applicable to other embodiments, and the scope of the present invention is not limited by such, rather by the scope of the claims. Moreover, for better understanding and clarity of the description, some components in the drawings may not necessary be drawn to scale, in which some may be exaggerated relative to others, and irrelevant parts are omitted. 
     Please refer to  FIG. 1 , which illustrates a block diagram of a touch sensitive system  100  in accordance with an embodiment of the present invention. The touch sensitive system  100  comprises at least one transmitter  110 , a touch panel  120 , a touch sensitive processing apparatus  130 , and a host  140 . The transmitter  110  may be an active stylus which emits electric signal in one embodiment of the present invention. However, the implementations of the transmitter  110  are not restricted to that. The touch sensitive system  100  may comprises a plurality of transmitters  110 . The touch panel  120  is formed on a substrate. The touch panel  120  may be a touch sensitive screen. The present application does not limit implementations of the touch panel  120 . 
     In one embodiment, the touch sensitive area of the touch panel  120  includes a plurality of first electrodes  121  and a plurality of second electrodes  122 . Multiple capacitive coupling sensing points are located where the intersections of these two kinds of electrodes. The first and second electrodes  121  and  122  are connected to the touch sensitive processing apparatus  130 , respectively. In a mutual capacitance detecting mode, the first electrodes  121  may be called as driving electrodes, the second electrodes  122  may be called as sensing electrodes. The touch sensitive processing apparatus  130  provides driving voltage (voltage of driving signal) to those first electrodes  121  and measures signal variation occurs to the second electrodes  122  to detecting foreign conductive object approximating or touching the touch panel  120 . Ordinary people skilled in the art could understand the touch sensitive processing apparatus  130  could use self-capacitance mode or mutual-capacitance mode to detecting approximating or touching event and object. No description is elaborated further. In addition to self-capacitance mode or mutual-capacitance mode, the touch sensitive processing apparatus  130  could further detect the electric signal emitted from the transmitter  110  to calculate a position of the transmitter  110  in relative to the touch panel  120 . In one embodiment, signal variations occurs to the first electrodes  121  and the second electrodes  122  are measured, respectively, to detect the electric signal and the position of the transmitter  110  in relative to the touch panel  120 . Since frequency of the electric signal emitted from the transmitter  110  is not identical or harmonic to frequency of driving signals in self-capacitance mode or mutual-capacitance mode, the touch sensitive processing apparatus  130  could distinguish the electric signals from the transmitter  110  and the driving signals during self-capacitance mode or mutual-capacitance mode. In another embodiment, the touch panel  120  may be surface capacitance touch sensitive panel which has four electrodes attaching to four corners or four sides. The touch sensitive processing apparatus  130  detects the position of the transmitter  110  in relative to the touch panel  110  by measuring signal variations of these four electrodes. 
     A host  140  is also shown in  FIG. 1 . It could be a central processing unit, a master processor in an embedded system, or any other form of computer. In one embodiment, the touch sensitive system  110  could be a tablet computer. The host  140  could be a CPU which runs an operating system of the tablet computer. For example, the tablet computer relies on Android operating system and the host  140  is an ARM processor which runs Android operating system. The present application does not limit the format of information transmitted between the host  140  and the touch sensitive processing apparatus  130 . It only requires that the information is related to approximating or touching event occurs to the touch panel  120 . 
     Since electric signals are emitted, the transmitter  110  or active stylus needs electric power to supply the energy of electric signals. In one embodiment, power source of the transmitter  110  may be battery or a rechargeable battery. Alternatively, power source of the transmitter  110  may be capacitor, especially a ultra-capacitor or a super-capacitor, such as one of EDLC (Electrical Double Layered Capacitor), pseudo-capacitor, and hybrid capacitor. The charging time of ultra-capacitor is counted in seconds and the discharging time is counted in hours. In other words, active stylus endures long requiring short charging time. 
     In one embodiment, the touch panel  120  periodically emits a beacon signal. When the tip of the transmitter  110  or active stylus contacts the touch panel  120 , the transmitter  110  could detect the beacon signal via the tip. In response to the detection, the transmitter  110  begins to emit the electric signal for a while to the touch panel  120 . Consequently, the transmitter  110  may stop emitting the electric signal if no beacon signal is detected. Thus the operating time of the transmitter could be extended accordingly. 
     The beacon signal could be emitted via the first electrodes  121  and/or the second electrodes  122 . In one embodiment, in case driving signals are transmitted from the first electrodes for mutual capacitance detection, frequency of the driving signals is not identical or harmonic to frequency of the beacon signal. Therefore it is possible to transmit the driving signals and the beacon signals simultaneously. In other words, mutual-capacitance detection and the electric signal detection could be performed simultaneously. Alternatively, it takes turn to transmit the driving signals and the beacon signals. Thus mutual-capacitance detection and the electric signal detection are done in time-sharing fashion. In such case, frequency of the driving signals may or may not be identical to frequency of the beacon signals. 
     In one embodiment, in order to make the transmitter  110  detecting the beacon signals further away above the touch panel  120 , the touch sensitive processing apparatus  130  commands all of the first and the second electrodes  121  and  122  of the touch panel  120  emitting the driving signals simultaneously, such that the total signal strength emitted from the touch panel  120  could be maximized. 
     Please refer to  FIG. 2 , which depicts a block diagram of a transmitter  110  in accordance with an embodiment of the present invention. The transmitter  110  comprises a first signal source  211 , a second signal source  212 , a first component  221  with a first impedance Z1, a second component  222  with a second impedance Z2, and a tip section  230 . A first signal emitted from the first signal source  211  transmits to the touch panel  120  via the first component  221  and the tip section  230 . Similarly, a second signal emitted from the second signal source  212  transmits to the touch panel  120  via the second component  222  and the tip section  230 . 
     In one embodiment, the first signal includes a signal with a first frequency f1, the second signal includes a signal with a second frequency f2. The first signal with frequency f1 and the second signal with frequency f2 may be square-wave signals, sinuous signals, or PWM (pulse width modulation) signals. In one embodiment, the first frequency f1 is not identical or harmonic to frequency of the beacon signal and frequency of the driving signal. The second frequency f2 does not equal to the first frequency f1. Furthermore, the second frequency f2 is not identical or harmonic to frequency of the beacon signal and frequency of the driving signal. 
     These signals with two frequencies get mixed and fed into the tip section  230  via the first component  221  with the first impedance Z1 and the second component  222  with the second impedance Z2, respectively. The first and second components  221  and  222  could be any combination of resistor, inductor, and capacitor (e.g. solid state capacitor). In the embodiment as shown in  FIG. 2 , the second impedance Z2 is fixed or constant; the first impedance Z1 is variable or adjustable corresponding to a sensing variation of a sensor. 
     In another embodiment, the first and second impedances Z1 and Z2 both are variable or adjustable. A ratio of these two impedances is corresponding to a sensing variation of a sensor. In one embodiment, the sensor may be a contractible and flexible tip. The first impedance Z1 changes corresponding to the stroke or the pressure level of the flexible tip. In some examples, the first impedance Z1 is linearly proportional to the variation of the sensing value of the sensor. In alternative examples, the first impedance Z1 is non-linearly proportional to the variation of the sensing value of the sensor. 
     The first and second components  221  and  222  may not be the same kind of electric component. For example, the first component  221  is a resistor and the second component  222  is a capacitor, and vice versa. In another example, the first component  221  is a resistor and the second component  222  is an inductor, and vice versa. Alternatively, the first component  221  is an inductor and the second component  222  is a capacitor, and vice versa. At least one of the first impedance Z1 and the second impedance Z2 is variable or adjustable. For example, it may be resistor with variable resistance, capacitor with variable capacitance, or inductor with variable inductance. In case of one of the first impedance Z1 and the second impedance Z2 is fixed or constant; the component may be one of the following: resistor with fixed resistance, capacitor with fixed capacitance, or inductor with fixed inductance. 
     In one embodiment, the first component  221  may be a FSR, force sensing resistor, with a variable and determinable resistance corresponding to an applied force, and the second component  222  may be a resistor with fixed resistance. In alternative embodiment, the first component may be a resistor with variable resistance. Hence, while other conditions are the same, a ratio of a first strength M1 of signal component with the first frequency f1 and a second strength M2 of signal component with the second frequency f2 in the electric signals emitted from the tip section  230  is proportional to an inverse ratio of the first and the second impedances Z1 and Z2. In other words, M1/M2=k (Z2/Z1). 
     When the transmitter  110  hovers above the touch panel  120 , since the tip section  230  is not pressed or moved, the ratio between strength M1 of signal component with the first frequency f1 and strength M2 of signal component with the second frequency f2 is a constant or a predetermined value. Or alternatively, a ratio of (M1−M2)/(M1+M2) or another ratio of (M2−M1)/(M1+M2) is also a constant or a predetermined value. In addition, the pressure level may be represented as M1/(M1+M2) or M2/(M1+M2). Except for those four ratios mentioned above, ordinary people skilled in the art could use any other ratio involving strengths M1 and M2. In other words, when the detected ratio is the constant or the predetermined value, it is concluded that the sensor did not sense any variation. In one embodiment, it means that the transmitter  110  does not contact the touch panel  120 . 
     When the transmitter  110  contacts the touch panel  120 , the tip section  230  is pressed to move. The first impedance Z1 of the first component  221  changes according to the movement or the pressure of the tip section  230  such that the ratio of M1 and M2 is varied accordingly from the constant or the predetermined value. The touch panel  120  could generate corresponding sensing (pressure) value according to the ratio. The fore-mentioned constant or predetermined value may not be a number but a range with a tolerable error. 
     It is noticeable that the relation between the ratio and the sensing value may not be linear. Furthermore, the sensing value may not be linearly proportional to the movement or the pressure of the sensor. The sensing value is just a value sensed by the touch panel  120 . The present application does not limit the correspondence of the sensing value. For example, the touch panel  120  could generate the sensing value according to the ratio by looking into a look-up table or by calculations. 
     Please refer to  FIG. 3 , which shows a block diagram of a transmitter  110  in accordance with an embodiment of the present invention. Similar to the embodiment shown in  FIG. 2 , the transmitter  110  comprises the first signal source  211 , the second signal source  212 , a first capacitor  321  with a first capacitance C1, a second capacitor  322  with a second capacitance C2, and the tip section  230 . 
     The two signal sources  211  and  212  may be a first PWM signal source PWM1 and a second PWM signal source PWM2, respectively. These two signal sources  211  and  212  may emit signals with the same frequency or not. The transmitter  110  comprises the second capacitor  322  with fixed second capacitance C2 and the first capacitor  321  with a variable first capacitance C1, which are connected to the signal sources PWM2  212  and PWM1  211 , respectively. Since the first capacitance C1 changes according to the pressure level of the tip section  230 , the embodiment shown in  FIG. 3  may comprises a capacitive force sensor or a FSC, force sensing capacitor. In one embodiment, the capacitive force sensor may be implemented by PCB (printed circuit board) or any other material. The structure of the FSC would be described in paragraphs below. 
     The strength ratio of these two signal sources is inversely proportional to resistances of these two capacitors  321  and  322 . When the tip section  230  of the stylus does not touch, or the force sensor does not sense any force, resistance of the first capacitor  321  remains the same. The resistance ratio of these two capacitors  321  and  322  keeps unchanged. When the transmitter  110  hovers above the touch panel  120  and the emitted electric signals are detected, the strength ratio of these two signal sources is constant or fixed. 
     However, if the tip section  230  of the transmitter  110  is touched or the force sensor does sense force, the resistance of the first capacitor  321  changes accordingly such that the resistance ratio of these two capacitors  321  and  322  also changes accordingly. When the transmitter  110  contacts the touch panel  120  and the emitted electric signals are detected, the strength ratio of these two signal sources is varied according to the force sensed by the force sensor. 
     Please refer to  FIG. 4A , which depicts a block diagram of a transmitter  110  in accordance with an embodiment of the present invention. Similar to the embodiment as shown in  FIG. 3 , the transmitter  110  comprises the first signal source  211 , the second signal source  212 , the first capacitor  321  with the first capacitance C1, the second capacitor  322  with the second capacitance C2, and the tip section  230 . The transmitter  110  may comprise multiple sensors to detect multiple states. In one embodiment, the tip section  230  comprises a force sensor for detecting the pressure level of the tip and reflecting the pressure level to the emitted electric signal. In another embodiment, the transmitter  110  may comprise multiple buttons, such as eraser button and barrel button. Alternatively, the transmitter  110  may include a switch to reflect whether the tip is touched by the touch panel or anything else. Persons having ordinary skill in the art could understand that the transmitter  110  may include more buttons and other forms of sensors but not limited to those mentioned. 
     In the embodiment shown in  FIG. 4A , the first capacitor  321  connects to an eraser capacitor  441  and a barrel capacitor  442  in parallel, which are connected in series to the eraser button and the barrel button, or switch SWE and switch SWB, respectively. When the corresponding button is pressed or the corresponding switch is shorted, the capacitor  441  or  442  is connected to the first capacitor  321  in parallel, such that it changes the capacitance of the PWM1 signal path and the resistance ratio between the PWM1 signal path and the PWM2 signal path is changed accordingly. Thus the strength ratio of these two signal sources is varied in consequence. 
     Since the capacitance C1 and resistance of the first capacitor  321  is variable, in case it is connected in parallel with the eraser capacitor  441  and the barrel capacitor  442 , the resistance ratio of the connected circuit and the second capacitor  322  resides in a range. In the embodiment as shown in  FIG. 4A , assuming the signal strength ratio of PWM1 versus PWM2 falls into a first range in response to the variable range of the first capacitor  321 . In case the first capacitor  321  is connected with the barrel capacitor  442  in parallel, i.e., the barrel button is pressed, the signal strength ratio of PWM1 versus PWM2 falls into a second range. In case the first capacitor  321  is connected with the eraser capacitor  441  in parallel, i.e., the eraser button is pressed, the signal strength ratio of PWM1 versus PWM2 falls into a third range. Further, in case the first capacitor  321  is connected with the barrel capacitor  442  and the eraser capacitor  441  in parallel, i.e., the barrel button and the eraser button are pressed, the signal strength ratio of PWM1 versus PWM2 falls into a fourth range. In the implementation, the capacitance and resistance of the barrel capacitor  442  and the eraser capacitor  441  could be adjusted such that the first, second, third, and four ranges are not overlapped. Because the ranges are not overlapped, it is able to determine which button is pressed according to which range the signal strength ratio falls into. In consequence, the pressure level of the force sensor could be concluded according to the signal strength ratio. 
     Please refer to  FIG. 4B , which depicts a block diagram of a transmitter  110  in accordance with an embodiment of the present invention. Comparing with the embodiment shown in  FIG. 4A , the second capacitor  322  is configured to connected with the eraser capacitor  441  and the barrel capacitor  442 , which are connected in series to the eraser button and the barrel button, or switch SWE and switch SWB, respectively. When the corresponding button is pressed or the corresponding switch is shorted, the capacitor  441  or  442  is connected to the second capacitor  322  in parallel, the resistance ratio between the PWM1 signal path and the PWM2 signal path is changed accordingly. Thus the strength ratio of these two signal sources is varied in consequence. 
     Since the capacitance C1 and resistance of the first capacitor  321  is variable, in case the second capacitor  322  is connected in parallel with the eraser capacitor  441  and the barrel capacitor  442 , the resistance ratio of the connected circuit and the first capacitor  321  resides in a range. In the embodiment shown in  FIG. 4B , assuming the signal strength ratio of PWM1 versus PWM2 falls into a first range in response to the variable range of the first capacitor  321 . In case the second capacitor  322  is connected with the barrel capacitor  442  in parallel, i.e., the barrel button is pressed, the signal strength ratio of PWM1 versus PWM2 falls into a fifth range. In case the second capacitor  322  is connected with the eraser capacitor  441  in parallel, i.e., the eraser button is pressed, the signal strength ratio of PWM1 versus PWM2 falls into a sixth range. Further, in case the second capacitor  322  is connected with the barrel capacitor  442  and the eraser capacitor  441  in parallel, i.e., the barrel button and the eraser button are pressed, the signal strength ratio of PWM1 versus PWM2 falls into a seventh range. 
     Utilizing the same spirit embodied in  FIG. 4A , the capacitance and resistance of the barrel capacitor  442  and the eraser capacitor  441  could be adjusted such that the first, fifth, sixth, and seventh ranges are not overlapped. Because the ranges are not overlapped, it is able to determine which button is pressed according to which range the signal strength falls into. In consequence, the pressure level of the force sensor could be concluded according to the signal strength ratio. 
     Please refer to  FIG. 5 , which depicts a block diagram of a transmitter  110  in accordance with an embodiment of the present invention. The embodiment as shown in  FIG. 5  may be variation of embodiments shown in  FIGS. 2, 3, 4A, and 4B . Reversely, the variation of the embodiment shown in  FIG. 5  apply to the embodiments shown in  FIGS. 2, 3, 4A, and 4B . 
     Comparing with the embodiment shown in  FIG. 2 , the embodiment shown in  FIG. 5  further comprises a ring electrode  550  and a ring wire  551 . The ring wire  551  as shown in  FIG. 5  connects to a third signal source  513  via a ring capacitor  523  with a fixed capacitance Cr. The tip section  230  is surrounded by the ring electrode  550  which is coupled to the ring wire  551  and the printed circuit board in the aft. Although it is called “ring” electrode  550  in the present application, the ring electrode  550  may comprise multiple electrodes in some embodiments. The present invention does not limit the number of the ring electrode  550 . For convenience, they are collectively called ring electrode  550 . The ring electrode  550  is electrically insulated to the tip section. They are not electrically coupled. 
     Six switches Sw1 through Sw6 are shown in  FIG. 5 . The tip section  230  radiates signals from the first signal source  211  if the switch Sw1 is shorted and switch Sw2 is opened. Otherwise, it could be done if the switch Sw1 is opened or in case the switches Sw1 and Sw2 are shorted. Similarly, the tip section  230  radiates signals from the second signal source  212  if the switch Sw3 is shorted and switch Sw4 is opened. Otherwise, it could be done if the switch Sw3 is opened or in case the switches Sw3 and Sw4 are shorted. The ring electrode  550  radiates signals from the third signal source  513  if the switch Sw5 is shorted and switch Sw6 is opened. Otherwise, it could be done if the switch Sw5 is opened or in case the switches Sw5 and Sw6 are shorted. 
     The first signal source  211  and the second signal source  212  may emit signals with different frequencies or signals with different frequency groups. Analogously, the third signal source  513  may emit signals with frequency or frequency group different to those from the first signal source  211  and the second signal source  212 . Similarly, the first signal source  211  and the second signal source  212  may transmit PWM signals. The frequency of signals transmitted from these two signal sources  211  and  212  may be identical or not. Comparably, the third signal source  513  may transmit PWM signals. The frequency of signals transmitted from these three signal sources  211 ,  212  and  513  may be identical or not. 
     Please refer to  FIG. 6 , which depicts a flow chart diagram of determining the sensing value of the tip of transmitter or active stylus performed by a processing apparatus in accordance with an embodiment of the present invention. The method could be executed by the touch sensitive processing apparatus  130  as shown in  FIG. 1 . The touch sensitive processing apparatus  130  connects multiple first electrodes  121  and second electrodes  122  of the touch panel  120  for detecting the electric signals emitted by the tip section  230  of the transmitter  110 . The touch sensitive processing apparatus  130  is able to determine a position the transmitter  100  in relative to the touch panel  120  according to signal strengths received by individual first electrode  121  and second electrode  122 . In addition, method shown in  FIG. 6  is configured to determine the force sensing value of the transmitter  110 . In one instance, the force sensing value is the pressure level of the tip section  230 . 
     The embodiment shown in  FIG. 6  may be corresponding to the embodiments shown in  FIG. 2  through  FIG. 5 . The first two steps  610  and  620  are calculating signal strength M1 and M2 of the first signal source  211  and the second signal source  212 , respectively. These two steps  610  and  620  could be done simultaneously or in any order. In case the signal from the first signal source  211  with first frequency f1 and the signal from the second signal source  212  with second frequency f2, the signal strength M1 is the strength of signal with f1 and the signal strength M2 is the strength of signal with f2. In case the signal from the first signal source  211  with first frequency group F1 and the signal from the second signal source  212  with second frequency group F2, the signal strength M1 is sum of strength of signals with each frequency of group F1 and the signal strength M2 is sum of strength of signals with each frequency in group F2. As mentioned above, the frequency in this embodiment could be PWM frequency. 
     Then in step  630 , calculating a ratio according to M1 and M2. Five examples of the ratio are already enumerated above, such as M1/M2, (M1−M2)/(M1+M2), (M2−M1)/(M1+M2), M1/(M1+M2), and M2/(M1+M2). Persons having ordinary skill in the art could use any other ratio involving M1 and M2 in addition to those examples. Next, step  640  is performed for determining whether the ratio is a predetermined value or falls into a predetermined range. If the result is true, the flow goes to step  650 . It is determined that the transmitter  110  is hovering above the touch panel  120 . Otherwise, the flow executes step  660  for calculating a sensing value of the tip section  230  according to the ratio. The sensing value may or may not be relevant to the pressure level or moving distance of the tip section  230 . The calculations of the sensing value could be done by looking into a lookup table, linear interpolation, and/or quadratic curve interpolation. It depends on the relation between the ratio and the sensing value. 
     When the method shown in  FIG. 6  applies to the embodiments shown in  FIGS. 4A and 4B , additional steps could be performed in step  660 . For example, when it applies to the embodiment shown in  FIG. 4A , the flow may further determine which one of the first, second, third, and fourth ranges the ratio calculated in step  630  falls into. Hence, it is able to determine whether the barrel button and/or the eraser button are pressed or not in addition to the sensing value of the tip section  230 . Analogously, when it applies to the embodiment shown in  FIG. 4B , the flow may further determine which one of the first, fifth, sixth, and seventh ranges the ratio calculated in step  630  falls into. Hence, it is able to determine whether the barrel button and/or the eraser button are pressed or not in addition to the sensing value of the tip section  230 . 
     In one embodiment of the present application, the controller or circuit inside the transmitter  110  does not need to determine the pressure level of the tip section  230 . It simply requires that one or both the first impedance Z1 of the first component  221  and the second impedance Z2 of the second component  222  change according to the pressure level of the tip section  230  such that one of the signal strength of first frequency f1 or first frequency group F1 and the signal strength of second frequency f2 or second frequency group F2 change in consequence. Therefore the pressure level of the tip section  230  could be calculated according to a ratio between the strength M1 of signals with first frequency f1 or first frequency group F1 and the strength M2 of signals with second frequency f2 or second frequency F2 is demodulated from the electric signals received by the touch panel  120 . 
     Please refer to  FIG. 7A , which illustrates a block diagram of a transmitter  110  in accordance with an embodiment of the present invention. Comparing with embodiments shown in  FIG. 2  through  FIG. 5 , the transmitter  110  shown in  FIG. 7A  also comprises a first component  221  with a first impedance Z1, a second component  222  with a second impedance Z2, and a tip section  230 . The first component  221  and the second component  222  may be any combination of resistor, inductor, and capacitor. In the embodiment as shown in  FIG. 7A , the second impedance Z2 may be fixed and the first impedance Z1 is variable or adjustable corresponding to a variation of a sensor, such as pressure level of the tip section  230 . The first component  221  and the second component  222  as shown in  FIG. 7A  could adopt those components with same numerals shown in  FIG. 2  through  FIG. 5 . No duplicated description is elaborated here. 
     Comparing with the previous embodiments, the difference resides in the embodiment shown in  FIG. 7A  is including a single signal source  714  which is configured to transmit electric signals to the first component  221  and the second component  222  and a controller  760  which is configured to measure a first current value I1 and a second current value I2 outputted from the first component  221  and the second component  222 , respectively. The controller  760  is further configured to calculated a ratio which may be one of the followings: I1/(I1+I2), 12/(I1+I2), I1/I2, (I1−I2)/(I1+I2), (I2−I1)/(I1+I2) and etc. Persons having ordinary skill in the art can calculated any other ratio involving the current values I1 and I2. 
     The calculated ratio could be used to conclude the pressure level of the tip section  230 . The controller  760  can transmit information derived from the first current value I1 and the second current value I2 via a transmitter wireless communication unit  770 . The host  140  may receive the information via a host wireless communication unit  780  to get the pressure level of the tip section  230 . 
     Please refer to  FIG. 7B , which illustrates a block diagram of a transmitter  110  in accordance with an embodiment of the present invention. The difference to the embodiment shown in  FIG. 7A  resides that the controller  760  may transmit information derived from the first current value I1 and the second current value I2 via a transmitter wired communication unit  771 . The host  140  may receive the information via a host wired communication unit  781  to get the pressure level of the tip section  230 . 
     Please refer to  FIG. 7C , which illustrates a block diagram of a transmitter  110  in accordance with an embodiment of the present invention. The difference to the embodiment shown in  FIG. 7B  resides that the transmitter  110  no longer has the single signal source  714 . Instead, the transmitter  110  uses the electric signal from the transmitter wired communication unit  771  as the signal source. Since the transmitter wired communication unit  771  is connected to the host wired communication unit  781 , the electric signal is supplied by the power of the host  140 . 
     Please refer to  FIG. 7D , which illustrates a block diagram of a transmitter  110  in accordance with an embodiment of the present invention. The difference to the embodiment shown in  FIG. 7A  resides that the transmitter  110  no longer has the single signal source  714 . Instead, the transmitter  110  uses received signal from the first electrodes  121  and/or the second electrodes  122  of the touch panel  120  when the tip section  230  approximating or touching the touch panel  120 . 
     It is worthy mentioned that the embodiments shown in  FIG. 7A through 7D  could use the variation shown in  FIG. 3 . The first component  221  may be the fore-mentioned first capacitor  321 . The second component  222  may be the fore-mentioned second capacitor  322 . Similarly, the embodiments shown in  FIG. 7A through 7D  could use the variations shown in  FIGS. 4A and 4B . The first component  221  may be connected with component corresponding to other switch in parallel, or the second component  222  may be connected with components corresponding to other switch in parallel, such that the controller  760  could conclude the state of the switch according to which range where the calculated ratio falls into. 
     Please refer to  FIG. 8 , which shows a flow chart of determining a sensing value of the tip section of the transmitter performed by a touch sensitive processing apparatus in accordance with an embodiment of the present invention. The embodiment shown in  FIG. 8  is quite similar to the embodiment shown in  FIG. 6 , which is configured to calculate the sensing value according to a ratio between a signal strength M1 of a first frequency (group) and a signal strength M2 of a second frequency (group). The embodiment shown in  FIG. 8  is configured to apply to implementation with a single signal source, which is configured to calculate the ratio between a first current value I1 through the first component  221  and a second current value I2 through the second component  222 . 
     The method may be executed by the controller  760  of the embodiments shown in  FIG. 7A through 7D . The first two steps  810  and  820  are configured for calculating a first current value I1 through the first component  221  and a second current value I2 through the second component  222 , respectively. These two steps  810  and  820  may be performed simultaneously, or in any order. Next, in step  830 , calculating a ratio of I1 and I2. Several examples of the ratio are already enumerated above, such as I1/(I1+I2), I2/(I1+I2), I1/I2, I2/I1, (I1−I2)/(I1+I2), (I2−I1)/(I1+I2), and etc. Next, in step  840 , determining whether the ratio is a predetermined value or falls into a predetermined range. If the result is true, the flow goes to step  850 , it is determined that the transmitter is hovering above the touch panel  120 . Otherwise, the flow goes to step  860 , calculating a sensing value of the tip section according to the ratio. The sensing value may or may not be relevant to the pressure level or moving distance of the tip section  230 . The calculations of the sensing value could be done by looking into a lookup table, linear interpolation, and/or quadratic curve interpolation. It depends on the relation between the ratio and the sensing value. 
     When the method shown in  FIG. 8  applies to the embodiments shown in  FIGS. 4A and 4B , additional steps could be performed in step  860 . For example, when it applies to the embodiment shown in  FIG. 4A , the flow may further determine which one of the first, second, third, and fourth ranges the ratio calculated in step  830  falls into. Hence, it is able to determine whether the barrel button and/or the eraser button are pressed or not in addition to the sensing value of the tip section  230 . Analogously, when it applies to the embodiment shown in  FIG. 4B , the flow may further determine which one of the first, fifth, sixth, and seventh ranges the ratio calculated in step  830  falls into. Hence, it is able to determine whether the barrel button and/or the eraser button are pressed or not in addition to the sensing value of the tip section  230 . 
     Please refer to  FIG. 9A , which shows a timing sequence of signal modulation in accordance with an embodiment of the present invention. The embodiment shown in  FIG. 9A  may apply to the transmitter  110  as shown in  FIG. 2  through  FIG. 5 . The horizontal axis of  FIG. 9A  is a time axis by order from left to right. As shown in  FIG. 9A , an optional noise detection period is included prior to a beacon signal is emitted by the touch panel  120 . The noise detected during the period may come from touch panel, the electronics, and/or background environment. The touch panel  120  and the touch sensitive processing apparatus  130  may detect one or more frequencies of noise signals. Noise detection would be described later. 
     In one embodiment, the touch panel  120  transmits beacon signals. The transmitter  110  comprises a demodulator for detecting the beacon signal. Please refer to  FIG. 29 , which illustrates a block diagram of a system for detecting beacon signal in accordance with an embodiment of the present invention. The system  2900  comprises a receiving electrode  2910 , a detecting module  2920 , and a demodulator  2930 . In one embodiment, the receiving electrode  2910  may be the ring electrode  550 , the tip section  230 , or any other electrodes. The receiving electrode  2910  forwards the received signal to the detecting module  2920 . 
     The detecting module comprises an analogous front end  2911  and a comparator  2912 . Persons having ordinary skill in the art could understand what analogous front end  2911  does which is not elaborated here. In this embodiment, the analogous  2911  outputs a voltage signal representing the signal strength. The comparator  2912  is configured to compare a reference voltage Vref and a voltage signal representing the signal strength. If the voltage signal is higher than the reference voltage, it means that the received signal is strong enough. Thus, the comparator  2912  outputs an activation signal or an enable signal to the demodulator  2930  which is configured to demodulate the received signal to determine whether the received signal contains the frequency of the beacon signal. If the voltage signal is lower than the reference voltage, the comparator  2912  may output a disable signal to the demodulator  2930 . Therefore the demodulator  2930  stops demodulating the received signal. 
     When the transmitter  110  did not receive the beacon signal for a while, it could be switched to a sleep mode for shutting the demodulator  2930  down to reduce power consumption. However, since the power consumption of the detecting module  2920  is not significant, it could continue detecting whether the signal strength of the received signal is over a predetermined value in the sleep mode. Once it is more than the predetermined value, the transmitter  110  may switch from the sleep mode to an energy saving mode which consume more power for activating the demodulator  2930 . In the same time, the rest of the transmitter  110  may still rest in the power down state. If the demodulator  2930  determines that the received signal does not contain the beacon signal, the demodulator  2930  may be shut down after some time and the transmitter  110  switches from the energy saving mode back to the sleep mode which consume less power. Instead, if the demodulator  2930  determines that the received signal does contain the beacon signal, the demodulator  2930  can wake up the rest parts of the transmitter  110  such that the transmitter switches from the energy saving mode to normal working mode. 
     Now, back to embodiment of  FIG. 9A , after a delay period enduring L0 length, the transmitter  110  emits electric signal during T0 and T1 periods. There may exist a delay period enduring L1 length between the T0 and T1 periods. The length of T0 period may or may not equal to the length of T1 period. The T0 and T1 periods are collectively called a signal frame. The touch sensitive processing apparatus  130  detects the electric signals emitted from the transmitter  110  during T0 and T1 periods. Next, after another optional delay time enduring L2 length, the touch sensitive processing apparatus  130  may perform optional other detection, e.g., fore-mentioned capacitance detection mode for detecting passive stylus or finger. 
     The present invention does not limit the lengths of delay times L0, L1, and L2, which may be zero or any other duration. The lengths of delay times L0, L1, and L2 may or may not be relevant. In one embodiment, among those periods shown in  FIG. 9A , only the T0 and T1 periods of the signal frame are mandatory, other periods are optional. 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                   
                 Barrel 
                 Eraser 
                   
               
               
                   
                   
                   
                 button 
                 button 
               
               
                 State 
                 Signal Source 
                 Period 
                 pressed 
                 pressed 
                 Other state 
               
               
                   
               
             
            
               
                 hovering 
                 1 st  signal source 
                 T0 
                 F0 
                 F1 
                 F0 
               
               
                   
                   
                 T1 
                 F1 
                 F2 
                 F2 
               
               
                   
                 2 nd  signal source 
                 T0 
                 F0 
                 F1 
                 F0 
               
               
                   
                   
                 T1 
                 F1 
                 F2 
                 F2 
               
               
                   
               
            
           
         
       
     
     Please refer to Table 1, which shows a modulation table of electric signals emitted by the transmitter  110  in accordance with an embodiment of the present invention. As shown in Table 1, the state of the transmitter  110  is hovering, i.e., no pressure is measured by the force sensor. Since the tip section  230  of the transmitter  110  does not contact the touch panel  120 , the first and second signal sources  211  and  212  emit the same frequency group Fx simultaneously in the same period in order to enhancing the signal strength in the embodiment shown in Table 1. For example, in case the barrel button is pressed, these two signal sources both emits frequency group F0 during the T0 period and frequency F1 during the T1 period. If the touch sensitive processing apparatus  130  detects signals with frequency group F0 during the T0 period and signals with frequency group F1 during the T1 period, it is determined that the barrel button of the hovering transmitter  110  is pressed. 
     The frequency group Fx comprises at least one frequency. Frequencies classified in the same frequency group are interchangeable. For example, frequency group F0 comprises f0 and f3 frequencies; frequency group F1 comprises f1 and f4 frequencies; and frequency group F2 comprises f2 and f5 frequencies. No matter which one of f0 and f3 frequencies is detected, the touch sensitive processing apparatus  130  takes that frequency group F0 is received. 
     In another embodiment, it is not required to have both signal sources  211  and  212  of the transmitter  110  emitting signals with the same frequency group. Table 1 is just an example of the present embodiment. Besides, the transmitter  110  may comprises more buttons or sensors. The present invention does not limit to two buttons. 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                   
                   
                   
                 Barrel 
                 Eraser 
                   
               
               
                   
                   
                   
                 button 
                 button 
               
               
                 State 
                 Signal Source 
                 Period 
                 pressed 
                 pressed 
                 Other state 
               
               
                   
               
             
            
               
                 Touching 
                 2 nd  signal source 
                 T0 
                 F0 
                 F1 
                 F0 
               
               
                   
                   
                 T1 
                 GND 
                 GND 
                 GND 
               
               
                   
                 1 st  signal source 
                 T0 
                 GND 
                 GND 
                 GND 
               
               
                   
                   
                 T1 
                 F1 
                 F2 
                 F2 
               
               
                   
               
            
           
         
       
     
     Please refer to Table 2, which shows a modulation table of electric signals emitted by the transmitter  110  in accordance with an embodiment of the present invention. As shown in Table 2, the state of the tip section  230  of the transmitter  110  is touching, i.e., pressure is measured by the force sensor. 
     With regard to the embodiment shown in  FIG. 4A , the following describes what happened if the barrel button is pressed. During the T0 period, the first signal source output is grounded and the second signal source emits signals with frequency group F0. During the T1 period, the second signal source output is grounded and the first signal source emits signals with frequency group F1. Furthermore, since the impedance of the first capacitor  321  is changed in the touching state, the pressure level of the tip section  230  could be calculated according to the signal strengths with regard to frequency groups F0 and F1 during the T0 and T1 periods, respectively. Besides, because the touch sensitive processing apparatus  130  detects frequency group F0 during the T0 period and detects frequency group F1 during the T1 period, it is determined that the barrel button is pressed. 
     With regard to the embodiment shown in  FIG. 4A , the following describes what happened if the barrel button is pressed. During the T0 period, the first signal source output is grounded and the second signal source emits signals with frequency group F0. The second capacitor  322  is connected with the barrel capacitor  442  in parallel. Although the electric signals emitted from the transmitter  110  during the T0 period only contains signals with frequency group F0 from the 2 nd  signal source, the signal strength is different from the one which the barrel button is not pressed. During the T1 period, the second signal source output is grounded and the first signal source emits signals with frequency group F1. Furthermore, since the impedance of the first capacitor  321  is changed in the touching state, the pressure level of the tip section  230  could be calculated according to the signal strengths with regard to frequency groups F0 and F1 during the T0 and T1 periods, respectively. Besides, because the touch sensitive processing apparatus  130  detects frequency group F0 during the T0 period and detects frequency group F1 during the T1 period, it is determined that the barrel button is pressed. 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 3 
               
               
                   
               
               
                   
                   
                   
                 Barrel 
                 Eraser 
                   
               
               
                   
                   
                   
                 button 
                 button 
               
               
                 State 
                 Signal Source 
                 Period 
                 pressed 
                 pressed 
                 Other state 
               
               
                   
               
             
            
               
                 hovering 
                 2 nd  signal 
                 T0 
                 F0 
                 F1 
                 F2 
               
               
                   
                 source 
                 T1 
                 F0 
                 F1 
                 F2 
               
               
                   
                 1 st  signal 
                 T0 
                 F0 
                 F1 
                 F2 
               
               
                   
                 source 
                 T1 
                 F0 
                 F1 
                 F2 
               
               
                   
               
            
           
         
       
     
     Please refer to Table 3, which shows a modulation table of electric signals emitted by the transmitter  110  in accordance with an embodiment of the present invention. In this embodiment, according to the received frequency group, it is able to know which button is pressed. 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 4 
               
               
                   
               
               
                   
                   
                   
                 Barrel 
                 Eraser 
                   
               
               
                   
                   
                   
                 button 
                 button 
               
               
                 State 
                 Signal Source 
                 Period 
                 pressed 
                 pressed 
                 Other state 
               
               
                   
               
             
            
               
                 Touching 
                 2 nd  signal 
                 T0 
                 F0 
                 F1 
                 F2 
               
               
                   
                 source 
                 T1 
                 GND 
                 GND 
                 GND 
               
               
                   
                 1 st  signal 
                 T0 
                 GND 
                 GND 
                 GND 
               
               
                   
                 source 
                 T1 
                 F0 
                 F1 
                 F2 
               
               
                   
               
            
           
         
       
     
     Please refer to Table 3, which shows a modulation table of electric signals emitted by the transmitter  110  in accordance with an embodiment of the present invention. In this embodiment, according to the received frequency group, it is able to know which button is pressed. The pressure level of the tip section could be calculated according to a received signal strength ratio between the T0 and T1 periods. 
     Please refer to  FIG. 9B , which shows a timing sequence of signal modulation in accordance with an embodiment of the present invention. The embodiment is a variation of the embodiment shown in  FIG. 9A . The difference resides between these two embodiments shown in  FIGS. 9A and 9B  is that a noise detection taking place after the T1 period. After that, other detection is performed. 
     Please refer to  FIG. 9C , which shows a timing sequence of signal modulation in accordance with an embodiment of the present invention. The modulation shown in  FIG. 9C  may apply to the transmitter  110  shown in  FIG. 5 . One additional function of the ring electrode  550  is to enhancing emitted signal strength of active stylus. Thus the detection range of the hovering active stylus could be increased consequently. 
     The modulation shows in  FIG. 9C  is when the transmitter  110  is hovering. In this state, the time period which the transmitter  110  emits signals contains the R time period, merely. During this R period, both the ring electrode  550  and the tip section  230  transmit electric signals together. In one embodiment, the electric signals may come from the same signal source with the same frequency and modulations. For example, both the ring electrode  550  and the tip section  230  transmit signals from the signal source  513 . In another instance, both the ring electrode  550  and the tip section  230  may simultaneously transmit signals from the first, the second, and the third signal sources in turns, such that it utilizes the maximum power of each signal sources. The touch sensitive processing apparatus  130  can conclude the position the transmitter  110  is hovering above the touch panel  120  by detecting the electric signals emitted from the ring electrode  550  during the R period. If the electric signals from the ring electrode  550  and the tip section  230  comes from the same signal source or have the same frequency group, the signal strength would be maximized. In consequence, the detecting range of the hovering transmitter  110  by the touch panel  120  would be maximized. Alternatively, the transmitter  110  transmits electric signals via only the ring electrode  550  during the R period. 
     Please refer to  FIG. 9D , which shows a timing sequence of signal modulation in accordance with an embodiment of the present invention. The modulation shown in  FIG. 9D  may apply to the transmitter  110  shown in  FIG. 5 . In the embodiment shown in  FIG. 9C , a delay time or blank period L1 is included after the R period. The touch panel  120  performs other detection after the period L1. Comparing with the embodiment shown in  FIG. 9C , the period L1 in the embodiment shown in  FIG. 9D  is extended. Comparing with the embodiment shown in  FIG. 9E , the period L1 in the embodiment shown in  FIG. 9D  equals to the sum of L1, T0, L2, T1, and T3 periods. Thus, if no further electric signal could be detected by the touch sensitive processing apparatus  130  shown in  FIG. 9D , it is determined that the transmitter  110  is in the state of hovering. 
     Please refer to  FIG. 9E , which shows a timing sequence of signal modulation in accordance with an embodiment of the present invention. The modulation shown in  FIG. 9E  may apply to the transmitter  110  shown in  FIG. 5 . The embodiment shown in  FIG. 9E  is equivalent to add an R period prior to the time frame of the embodiment shown in  FIG. 9A . In this embodiment, no matter whether the tip section  230  is touched or not, the transmitter  110  always transmits electric signal from the tip section during the T0 and T1 periods such that some logic design for controlling could be omitted. However, comparing with the embodiments shown in  FIGS. 9C and 9D , the embodiment shown in  FIG. 9E  would waste power consumed during the T0 and T1 periods. On the other hand, the touch sensitive processing apparatus  130  no longer needs to perform detection during the R period as long as the electric signals from the tip section  230  could be detected during the T0 and T1 periods. It could be determined that whether the tip section  230  is pressed or not and further determined that the transmitter  110  is in the state of hovering or not. 
     Please refer to  FIG. 9F , which shows a timing sequence of signal modulation in accordance with an embodiment of the present invention. The modulation shown in  FIG. 9F  may apply to the transmitter  110  shown in  FIG. 5 . In the embodiment shown in  FIG. 9E , no proportional relation is defined over lengths of the R, T0, and T1 periods. Instead, in the embodiment shown in  FIG. 9F , the ratios between lengths of the R, T0, and T1 periods is 1:2:4. Assuming that the touch sensitive processing apparatus  130  could perform N sampling during one time unit, where N is a positive integer. Hence, touch sensitive processing apparatus  130  could perform N, 2N, and 4N samplings during the R, T0, and T1 periods, respectively. The present invention does not limit the ratios between the lengths of these three periods. In one instance, the period with the most powerful electric signal endures the shortest time; the period with the weakest electric signal endures the longest time. For examples, the ratios may be 1:3:2, 1:2:3, or etc. The design of ratios depends on the implementation. Although the paragraphs above enumerate modulations in two periods T0 and T1 merely, the present invention does not limit to that. More periods is applicable to the present invention. 
     In one embodiment, the transmitter  110  could transmit stronger electric signals in the state of hovering and transmit weaker electric signals in the state of touching. Consequently, it increases the chance for the touch sensitive processing apparatus  130  detects the transmitter  110  hovering above the touch panel  120 . When the transmitter  110  contacts the touch panel  120 , it further reduces the power consumption of the transmitter  110 . 
     For examples, in the embodiments shown in  FIGS. 9C and 9D , when the tip section  230  is not touched, the electric signal emitted during the R period is stronger than the electric signal emitted during the L1 period which corresponding to the T0 and T1 periods. 
     The signal modulation represents that the transmitter  110  is in the state of hovering. In such state, the signal frame the transmitter  110  emits electric signal contains only one R period. During this R period, both the ring electrode  550  and the tip section  230  transmit the electric signals concurrently. In one embodiment, the electric signals may be come from the same signal source and having the same frequency and/or modulation. In one instance, both the ring electrode  550  and the tip section  230  transmit signals from the third signal source  513 . Alternatively, the ring electrode  550  and the tip section  230  may transmit signals from the first, second, and third signal sources  211 ,  212 , and  513 . Hence the electric signal emitted during the R period is the sum of output powers of these three signal sources. 
     In the Table 1 embodiment shown in  FIG. 9A , when the transmitter  110  in the state of hovering, output power come from the first signal source  211  and the second signal source  212 . In the Table 2, when the transmitter  110  in the state of touching, output power come from one of first signal source  211  and the second signal source  212  during the T0 and T1 periods. Hence, the transmitter  110  emits stronger electric signal if the tip section is not touched and emits weaker electric signal if the tip section is pressed. 
     Similarly, in the Table 3, the transmitter  110  utilizes output power from both the first signal source  211  and the second signal source  212  in the state of hovering. Instead, in the Table 4, the transmitter  110  makes use of one of the first signal source  211  and the second signal source  212  during the T0 and T1 periods. Hence, the transmitter  110  emits stronger electric signal if the tip section is not touched and emits weaker electric signal if the tip section is pressed. 
     The reason for adding noise detection period in the embodiments shown in  FIG. 9A through 9F  is described below. Please refer to  FIG. 10 , which shows noise propagation path in accordance with an embodiment of the present invention. As shown in  FIG. 10 , the electronics  100  including the touch panel  120  emits noise signals with frequency f0, which is a member of frequency group F0. It is assumed that the frequency group F0 contains another member frequency f3. When user holds the electronics  100 , the noise with frequency f0 would propagate to the touch panel  120  via the user&#39;s finger. If no noise detection is performed, the touch panel  120  may take the noise with frequency f0 from the finger as the electric signal emitted by the transmitter  110 . Hence, if the noise with frequency f0 could be detected in advanced, it could be filtered out from the signal frame. 
     In case the transmitter  110  is capable to change frequency, it can automatically transmit signal with another member frequency f3 of the frequency group F0 if the noise with frequency f0 is detected. Consequently, during the periods of signal frame, the touch sensitive processing apparatus  130  detects signal with frequency f3 from the transmitter  110  and noise signal with frequency f0 from the finger. This confuses the touch sensitive processing apparatus  130 . Therefore it can perform a noise detection after the T1 period or the signal frame as the embodiment shown in  FIG. 9B . At this moment, since the transmitter  110  ceases transmitting signals with frequency f3 while the noise signal with frequency f0 from the finger and the touch panel  120  stands still, it could be determined by the touch sensitive processing apparatus  130  that the signal with frequency f3 detected during the time frame is the signal came from the transmitter  110 . 
     It is mentioned in the description related to  FIG. 2  that the signal strength ratio is changed according to impedance variation of the first component  221 . Please refer to  FIG. 11 , which depicts a structure diagram of a first capacitor  221  in accordance with an embodiment of the present invention. By changing the impedance of the first capacitor  221  to adjust the signal strength ratio of multiple frequencies. Traditional capacitor is formed by two plates of conducting metal. The capacitance C is proportional to the permittivity and the plate areas and inversely proportional to the distance between these two plates. 
     One aspect of the embodiment is to use a mechanic structure for transforming a displacement along the axis of the transmitter  110  to another displacement vertical or angled to the axis. By creating the displacement, the capacitance and first impedance Z1 of the first capacitor  221  are changed accordingly while keeps the capacitance and second impedance Z2 of the second capacitor  222  intact, such that the ratio between the signal strength M1 with first frequency (group) and the signal strength M2 with second frequency (group). 
     There exist three non-contacting metal plates shown in  FIG. 11 . The first capacitor  221  is formed by a first metal plate  1110  and a second metal plate  1120 . The second capacitor  222  is formed by the second metal plate  1120  and a third metal plate  1130 . In one instance, the first metal plate  1110  is formed on a flexible circuit board or printed circuit board which covers with insulating paint or dielectric plate. The second metal plate  1120  and the third metal plate  1130  are formed in the double sides of the same circuit board or printed circuit board which also covers with insulating paint or dielectric plate. The second metal plate  1120  is coupled to the fore-end tip section  230  through wiring. The tip is attached to a lifting element  1140  (e.g. the ramp means). A movement of the tip can directly or indirectly deform whole or part of the first metal plate  1110  (and flexible circuit board or PCB) such that a displacement vertical to along the axis of the transmitter  110  or stylus is created accordingly. 
     The first metal plate  1110  is supplied with electric signal with first frequency (group) and the third metal plate  1130  is supplied with electric signal with second frequency (group). Therefore current induced in the second metal plate  1120  generates signals with the first frequency (group) and the second frequency (group) which is sent to the touch panel  120  via the fore-end tip section  230 . When the tip section  230  is not pressed, the first metal plate  1110  and its circuit board do not have a displacement vertical to the axis of the transmitter  110 . However, when the tip section  230  is pressed, the ramp means  1140  transforms the force parallel to the axis to the direction vertical to the axis such that the circuit board of the first metal plate  1110  deforms and moves. Furthermore, the permittivity of the first capacitor  221  changes accordingly, so do the capacitance C1 and impedance Z1 of the first capacitor  221 . When the tip section  230  is pressed, the circuit board of the second metal plate  1120  and the third metal plate  1130  moves as a whole. Therefore the capacitance C2 and impedance Z2 of the second capacitor  222  remains the same. 
     Since the circuit board of the first metal plate  1110  deforms upward, the embodiment may include at least one supporting element  1150  to provide support downward for helping the circuit board of the first metal plate  1110  recover to the original shape after the pressure to the tip section  230  is dismissed. When the circuit board is not deformed, the supporting force provided by the supporting element may be zero. 
     In one example of the present embodiment, the capacitances of the first capacitor  221  and the second capacitor  222  may equals. If so, the permittivity, distance, and area of these two capacitors are the same. However, the present invention does not limit to the condition. It only requires that the touch sensitive processing apparatus  130  is known about the impedance ratio between these two capacitors of the transmitter  110 . 
     In this embodiment, expensive force sensing resistor is replaced by cheaper circuit board or PCB. Besides, if the capacitances of the first capacitor  221  and the second capacitor  222  are designed to be equal, permittivity of these two capacitors  221  and  222  would be varied in the same rate due to environmental change. Hence the default ratio could be maintained consequently. Besides, it does not require any active controlling component to adjust the ratio of these two impedances Z1 and Z2. The transmitter  110  could provide electric signal passively. So many resources could be saved. 
     Please refer to  FIG. 12 , which shows a diagram of reduced embodiment shown in  FIG. 11 . The circuit board, supporting element  1150 , and the wiring between the second metal plate  1120  and the tip section  230  are omitted. The description of embodiment shown in  FIG. 12  can reference those for  FIG. 11 . 
     Please refer to  FIG. 13 , which is a variation of the embodiment shown in  FIG. 12 . The third metal plate  1130  is moved to the aft of the first metal plate  1110  and they are not electrically coupled. When the tip section  230  is pressed, only the first metal plate  1110  and its circuit board deform. In some examples, the first metal plate  1110  and the third metal plate  1130  may be formed on the same circuit board. 
     Please refer to  FIG. 14 , which is a variation of the embodiment shown in  FIG. 13 . The first metal plate  1110  and the third metal plate  1130  comprise two plates A and B, respectively. They are feed into signals with first frequency (group) and second frequency (group), respectively. When the tip section  230  is pressed, the first metal plate A  1110 A, the first metal plate B  1110 B, and their circuit board deforms, but the third metal plate A  1130 A, the third metal plate B  1130 B, and their circuit board do not deform. Comparing with the embodiment shown in  FIG. 13 , since there are two deforming metal plates  1110 A and  1110 B, the impedance variation would be larger and more obvious than the variation of the embodiment shown in  FIG. 13 . 
     Please refer to  FIG. 15 , which is a variation of the embodiment shown in  FIG. 14 . The second metal plate  1120  also comprise two plate A  1120 A and plate B  1120 B, which are coupled to the tip section  230  through wiring. A first capacitor A  221 A is formed by the first metal plate A  1110 A and the second metal A  1120 A. A second capacitor A  222 A is formed by the second metal plate A  1120 A and the third metal plate A  1130 A. A first capacitor B  221 B is formed by the first metal plate B  1110 B and the second metal B  1120 B. A second capacitor B  222 B is formed by the second metal plate B  1120 B and the third metal plate B  1130 B. When the tip section is pressed, the first metal plate A  1110 A, the first metal plate B  1110 B, and their circuit boards deform. However, the third metal plate A  1130 A, the third metal plate B  1130 B, and their circuit boards remains the same. Comparing with the embodiment shown in  FIG. 13 , since there are two deforming metal plates  1110 A and  1110 B, the impedance variation would be larger and more obvious than the variation of the embodiment shown in  FIG. 13 . 
     Please refer to  FIG. 16A , which shows a structure in accordance with an embodiment of the present invention. In the embodiment shown in  FIG. 16A , there are a first metal plate  1110 , a second metal plate  1120 , and a third metal plate  1130  from top to bottom. The first metal plate  1110  and the third metal plate  1130  are fixed and fed in signals with first frequency (group) and second frequency (group), respectively. Current induced from the second metal plate  1120  generates electric signals mixed with first frequency (group) and second frequency (group). 
     A first capacitor  221  is formed by the first metal plate  1110  and the second metal plate  1120 . A second capacitor  222  is formed by the second metal plate  1120  and the third metal plate  1130 . When the second metal plate  1120  is not deformed, the impedances of the first capacitor  221  and the second capacitor  222  are fixed in the same environment. Hence a strength ratio of signal with first frequency (group) and signal with second frequency (group) contained in the electric signal could be calculated. If the ratio is a predetermined value or falls into a predetermined range, it is concluded that the second metal plate  1120  is not deformed. 
     If the second metal plate  1120  deforms, the impedances and capacitances of the first capacitor  221  and the second capacitor  222  change accordingly. In consequence, a strength ratio could be calculated according to these two signal strength values. Based on the variation of the ratio, the deforming and displacement of the second metal plate  1120  could be calculated. Steps shown in the embodiment of  FIG. 6  could be applicable here. 
     Please refer to  FIG. 16B , which is a variation of the embodiment shown in  FIG. 16A . The second metal plate  1120  and the third metal plate  1130  are fixed and fed in signals with first frequency (group) and second frequency (group), respectively. Current induced from the first metal plate  1110  generates electric signals mixed with first frequency (group) and second frequency (group). 
     A first capacitor  221  is formed by the first metal plate  1110  and the second metal plate  1120 . A second capacitor  222  is formed by the first metal plate  1110  and the third metal plate  1130 . When the first metal plate  1110  is not deformed, the impedances of the first capacitor  221  and the second capacitor  222  are fixed in the same environment. Hence a strength ratio of signal with first frequency (group) and signal with second frequency (group) contained in the electric signal could be calculated. If the ratio is a predetermined value or falls into a predetermined range, it is concluded that the first metal plate  1110  is not deformed. 
     If the first metal plate  1110  deforms, the impedances and capacitances of the first capacitor  221  and the second capacitor  222  change accordingly. In consequence, a strength ratio could be calculated according to these two signal strength values. Based on the variation of the ratio, the deforming and displacement of the first metal plate  1110  could be calculated. Steps shown in the embodiment of  FIG. 6  could be applicable here. The impedance may be changed according to variations of temperature and humanity. However, both impedances of the first capacitor  221  and the second capacitor  222  change together according to the environmental variations of temperature and humanity. Therefore, influence on the ratio caused by temperature and humanity could be reduced or eliminated. 
     Please refer to  FIGS. 17A and 17B , which show structural diagrams of the first capacitor and the second capacitor in accordance with an embodiment of the present invention. In the embodiment shown in  FIGS. 16A and 16B , signals with first frequency (group) and second frequency (group) are fed. However, in the embodiment shown in  FIGS. 17A and 17B , a driving signal with the same frequency is fed. In other words, the embodiments can be applicable to those embodiments shown in  FIGS. 7A through 7D . The driving signal fed in could be the signal source  714  of the embodiments shown in  FIGS. 7A and 7B . The electric signal from the transmitter wired communication unit  771  of the embodiment shown in  FIG. 7C  could be the signal source. Moreover, the electric signal received from the first electrodes  121  and/or the second electrodes  122  of the touch panel when the tip section  230  shown in  FIG. 7D  approximates or touches could be used as the signal source. 
     The structure of three metal plates as shown in  FIG. 17A  is identical to the structure of three metal plates as shown in  FIG. 16A . A driving signal with a frequency may feed into the deformable second metal plate  1120 . Due to capacitive effect between the second metal plate  1120 , the first metal plate  1110  outputs the induced current with a current value I1. Analogously, Due to capacitive effect between the second metal plate  1120 , the third metal plate  1130  outputs the induced current with a current value I2. 
     A first capacitor  221  is formed by the first metal plate  1110  and the second metal plate  1120 . A second capacitor  222  is formed by the second metal plate  1120  and the third metal plate  1130 . When the second metal plate  1120  is not deformed, the impedances of the first capacitor  221  and the second capacitor  222  are fixed. Hence, the current values I1 and I2 are analyzed and a ratio is calculated according to these two current values. When the ratio is a predetermined value or falls into a predetermined range, it is determined that the second metal plate  1120  is not deformed. 
     When the second metal plate  1120  is deformed, the impedances and capacitance of the first capacitor  221  and the second capacitor  222  are changed. Hence, a ratio is calculated according to these two current values. Based on the variation of the ratio, the deforming and displacement of the second metal plate  1120  could be deduced in consequence. The embodiment shown in  FIG. 8  could be applicable here. 
     Please refer to  FIG. 17B , which is a variation of the embodiment shown in  FIG. 17A . The second metal plate  1120  and the third metal plate  1130  are fixed. The driving signal with a frequency is fed into the deformable first metal plate  1110 . Due to capacitive effect between the first metal plate  1110 , the second metal plate  1120  outputs the induced current with a current value I1. Analogously, Due to capacitive effect between the first metal plate  1110 , the third metal plate  1130  outputs the induced current with a current value I2. 
     A first capacitor  221  is formed by the first metal plate  1110  and the second metal plate  1120 . A second capacitor  222  is formed by the first metal plate  1110  and the third metal plate  1130 . When the first metal plate  1110  is not deformed, the impedances of the first capacitor  221  and the second capacitor  222  are fixed. Hence, the current values I1 and I2 are analyzed and a ratio is calculated according to these two current values. When the ratio is a predetermined value or falls into a predetermined range, it is determined that the first metal plate  1110  is not deformed. 
     When the first metal plate  1110  is deformed, the impedances and capacitance of the first capacitor  221  and the second capacitor  222  are changed. Hence, a ratio is calculated according to these two current values. Based on the variation of the ratio, the deforming and displacement of the first metal plate  1110  could be deduced in consequence. The embodiment shown in  FIG. 8  could be applicable here. 
     Please refer to  FIG. 18 , which is a variation of the embodiment shown in  FIG. 11 . The embodiment shown in  FIG. 11  requires feeding signals with two different frequencies. Instead, in the embodiment shown in  FIG. 18  as well as those shown in  FIGS. 17A and 17B , it is required to feed driving signal with a frequency or some kind of signal, merely. No matter how many frequencies contained in the signal fed in. 
     A first capacitor  221  is formed by the first metal plate  1110  and the second metal plate  1120 . A second capacitor  222  is formed by the second metal plate  1120  and the third metal plate  1130 . Since the distance and permittivity between the second metal plate  1120  and the third metal plate  1130 , the capacitance and impedance of the second capacitor  222  is fixed. When the first metal plate  1110  is not deformed, the impedances of the first capacitor  221  and the second capacitor  222  are fixed. Hence, a ratio of analyzed current value I1 and I2 could be calculated. When the ratio is a predetermined value or falls into a predetermined range, it is determined that the first metal plate  1110  is not deformed. Moreover, the deforming of the first metal plate  1110  changes its own capacitance and impedance. Thus when it is deformed due to external force, the current value I1 is changed accordingly. In consequence, the ratio involving the current values I1 and I2 also changes. Based on the variation of the ratio, the deforming and displacement of the first metal plate  1110  could be deduced in consequence. The embodiment shown in  FIG. 8  could be applicable here. 
     In alternative embodiment of the present invention, the controller or circuit of the transmitter  110  may feed driving signal with a frequency into the second metal plate  1120  and calculate the current values I1 and I2 through the first capacitor  221  and the second capacitor  222 , respectively. By using the ratio of these two current values, a sensing value of pressure level of the tip section is deduced accordingly. In other words, utilizing the mechanism including the first impedance Z1 and the second impedance Z2, the present invention provides a design of FSC, force sensing capacitor, which may replace traditional force sensing components, such as FSR (force sensing resistor), for detecting pressure level. The FSC provided by the present invention has characteristics such as low cost and immune to influence of temperature and humanity. As shown in the figures above, FSC utilizing flexible PCB is disclosed by present invention. One aspect of the present application is to provide novel forms of FSC. 
     Please refer to  FIG. 19A , which depicts a profiling diagram of the FSC structure used in the transmitter  110  in accordance with an embodiment of the present invention. Please be noted that scales of  FIGS. 19A through 19E  are changed to highlight some important parts. Besides, some fixed components are omitted for simplifying the figure. As shown in  FIG. 19A , the most left component is a long rod tip or the tip section  230 , which is a conductor. For convenience, the tip section is at the fore end of the transmitter  110  or active stylus. When the tip section contacts the fore moving part  1971 , the tip section  230  is electrically coupled to the fore moving part  1971 . The fore-moving part  1971  could be joined together with a rear moving part  1972  by protruding fasteners in the middle of the fore moving part  1971  and corresponding recessed fasteners in the middle of the rear moving part  1972 . In one embodiment, the protruding and recessed fasteners comprise screw thread or whorl. Both the fore and rear moving parts  1971  and  1972  may be conductors or conductive elements, such as metal. 
     A shell component  1980 , shown in  FIG. 19A , circularly embraces the fore and rear moving parts  1971  and  1972 . Only parts of the shell component  1980  are illustrated in  FIG. 19A . A neck part with smaller diameter of the shell component  1980  is constructed nearby the tip section  230 . A shoulder part with larger diameter next to the neck part of the shell component is used to be a bearing part. As shown in  FIG. 19A , at least one elastic element  1978  is placed between the bearing part and the fore moving part  1971 . The elastic element  1978 , such as spring, elastic piece, or in any other forms, is supposed to provide force between the shell component  1980  and the fore moving part  1971  along the axis of the stylus. In some embodiments, the elastic element  1978  unlike the one shown in  FIG. 19A  is surrounded the moving part  1970  and the neck part of the shell component  1980 . 
     In another embodiment, the elastic element  1978  may provide force to both the shell component  1980  and the rear moving part  1972  along the axis of the stylus. Because a whole moving part  1970  composed of the fore and the rear moving parts  1971  and  1972  by fasteners, no matter which one of the fore and the rear moving part  1971  and  1972  is pressed, the whole moving part  1970  is pushed to the tip and the tip section  230  is also pushed forward accordingly. 
     In case the tip section  230  is pressed toward the right hand side of  FIG. 19A  or toward the rear, the force provided by the elastic element  1978  is compromised and the elastic element  1978  would be compressed such that a portion of the moving part  1970  touches the bearing part of the shell component  1980 . Hence, the design provided by the present application creates a stroke that moving part  1970  moves inside the neck part of the shell component  1980  along the axis of the stylus. Accordingly, the tip section  230  touching the moving part  1970  also moves the same distance of the stroke along the axis. The distance of the stroke could be varied according to different designs, e.g., 1 mm or 0.5 mm. The present invention does not limit the distance of the stroke. 
     In the rear of the rear moving part  1972 , a dielectric film  1973  is formed. In the rear of the dielectric film  1973 , a compressible conductor  1974  is arranged. In one embodiment, the compressible conductor  1974  may be a conductive rubber or an elastic element formed by conductors. A sandwich structure comprising the moving part  1970 , the dielectric film  1973 , and the compressible conductor  1974  makes a capacitor or a FSC. The FSC provided by the present invention may be applicable to the first capacitor  221  shown in  FIG. 2  through  FIG. 5 . In short, the FSC disclosed in the present application could be used in the embodiments. 
     The compressible conductor  1974  is attached to a conductor base  1975  which is further attached to an inner face of the shell component  1980  by fasteners. In case the moving part  1970  moves toward rear side or right hand side, the compressible conductor  1974  is compressed by the rear moving part  1972  because the conductor base  1975  is fixed. Thus the capacitance of the FSC is changed accordingly. 
     Because of the restriction of stylus shape, circuits and battery module may be placed in the rear of the conductor base  1975 . As shown in  FIG. 19A , those components are represented by a PCB  1990 . As a first plate of the FSC, the moving part  1970  is connected to the PCB through a moving part wire  1977 . As a second plate of the FSC, the conductor base  1975  is connected to the PCB  1990  through a base wire  1976 . 
     The base wire  1976  may be another elastic element. In some embodiments, the base wire  1976 , unlike the one shown in  FIG. 19A , is surrounded the conductor base  1975 . In other embodiments, the conductor base  1975  is not conductive. Hence the base wire  1976  is electrically coupling to the compressible conductor  1974  through the conductor base  1975 . 
     In one embodiment, the manufacturing method of the dielectric film  1973  is submerging the right hand side surface of the rear moving part  1972  in a dielectric liquid. After the liquid stayed on the surface dried, a dielectric film  1973  is naturally formed on the right hand side surface of the rear moving part  1972 . 
     Please refer to  FIG. 20 , which shows a profiling diagram of contact surface of the compressible conductor  1974  facing the dielectric film  1973 . The figure depicts four embodiments of the contact surface of the compressible conductor  1974  facing the dielectric film  1973 . The embodiment (a) shows a surface having a central bulge. The embodiment (c) shows a sloped surface. The embodiment (b) shows a conical surface. And the embodiment (d) illustrates a surface with multiple protruding bulges. The present application does not limit to the surfaces shown in those embodiments. 
     Although the surface attaching the dielectric film  1973  of the moving part  1970  is a plane surface, the present invention does not limit to that. The surface may be constructed as the surfaces shown in  FIG. 20 , such as having a central bulge, having multiple bulges, sloped, or conical. In other words, both the surfaces of the compressible conductor  1974  and the dielectric film  1973  are not planes in some embodiments. 
     Please refer to  FIG. 19B , which shows an assembled profiling diagram of the structure shown in  FIG. 19A . In the assembled structure, a single whole moving part  1970  is formed by the fore and the rear moving part  1971  and  1972 . The moving part  1970  and the bearing of the shell component  1980  are connected by the elastic element  1978 . The elastic force provide by the elastic element  1978  pushes the moving part  1970  toward and touches the tip section  230  until portion of the bearing of the shell component  1980  is touched by the rear moving part  1972 . A stroke d of the moving part  1970  is relative to the shell component  1980 . In this situation, the compressible conductor  1974  is not deformed or compressed. It is assumed that a first capacitance value provided by the FSC. 
     Please refer to  FIG. 19C , which shows another assembled profiling diagram of the structure shown in  FIG. 19A . Comparing with  FIG. 19B , the tip section  230  is pressed toward the rear side. Influenced by the movement of the tip section  230 , the moving part  1970  overcomes the force provided by the elastic element  1978  and moves the whole distance of the stroke d until the fore moving part  1971  touches the bearing of the shell component  1980 . In this situation, the compressible conductor  1974  is compressed by the moving part  1970  and the dielectric film  1973  and deformed. It is assumed that a second capacitance value provided by the FSC is different to the first capacitance value. 
     Between the positions shown in  FIGS. 19B and 19C , countless positions the moving part  1970  can stay. In other words, there exist countless compressible levels of the compressible conductors  1974 . Or the area of contact surface between the compressible conductor  1974  and the dielectric film  1973  could be varied indefinitely. Each of the positions, the compressed levels, or the areas can be corresponding to a particular capacitance value of the FSC. 
     Please refer to  FIG. 19D , which depicts a profiling diagram of the FSC structure used in the transmitter  110  in accordance with an embodiment of the present invention. Comparing to  FIG. 19B , the difference is that the compressible conductor  1974  and the dielectric film  1973  exchange their positions. Nevertheless, in case the moving part  1970  moves to the rear side, the compressible conductor  1974  is compressible by the dielectric film  1973  and deformed. The capacitance value of the FSC is changed accordingly. 
     Please refer to  FIG. 19E , which depicts a profiling diagram of the FSC structure used in the transmitter  110  in accordance with an embodiment of the present invention. Comparing with  FIG. 19B , the differences include that a compressible dielectric material  1979  rather than the dielectric film  1973  is place in the right hand side of the rear moving part  1972 . The compressible dielectric material  1979  may be dielectric rubber, plastic, foam or etc. The conductor attached to the conductor base  1975  is replaced by an incompressible conductor such as metal or graphite. When pressed by the moving part  1970 , the thickness of the compressible dielectric material  1979  decreases, the distance between the moving part  1970  and the conductor also decreases consequently. Hence the capacitance of the FSC is changed accordingly. However, the cost of the incompressible conductor shown in  FIG. 19E  is more expensive than the compressible conductor shown in  FIG. 19A . 
     In a variation of the embodiment shown in  FIG. 19E , the contact surface of the conductor facing the compressible dielectric material  1979  may adopt those shown in  FIG. 20 . In another variation, the contact surface of the compressible dielectric material  1979  facing the conductor may adopt those shown in  FIG. 20 . 
     Similar to the embodiment shown in  FIG. 19D , the positions of the compressible dielectric material  1979  and the conductor may be exchanged such that the compressible dielectric material  1979  is attached to the conductor base  1975  and the conductor is attached to the rear of the moving part  1970 . When the moving part  1970  moves to the rear side, the conductor causes the compressible dielectric material  1979  deformed such that the capacitance of the FSC is changed accordingly. 
     Please refer to  FIG. 21 , which illustrates a pressure sensor according to an embodiment of the present invention. As shown in the figure, the pressure sensor  2110  has two input terminals a and b and an output terminal c, which are all connected to a control unit  2120 . The control unit  2120  feeds signals with first frequency (group) F1 and second frequency (group) F2 into the input terminals a and b, respectively, and receives the output signal of the pressure sensor  2120 . The control unit  2120  may embody the method disclosed in  FIG. 6 . 
     When external pressure makes capacitance change of a capacitor C1, the control unit  2120  could deduce the pressure according to the capacitance change. Hence, the pressure sensor  2110  could be widely adapted to pressure measure devices such as weight sensor. In one application, the pressure sensor  2120  could be used in another form of stylus. After the pressure on the tip of the stylus is deduced, the control unit  2120  drives a signal transmitter for transmitting an electric signal with a predetermined frequency f0 to a touch panel. 
     It is mentioned that the transmitter  110  may transmit the electric signal at some time after receiving the beacon signals emitted from the touch panel  120 , such that the touch panel  120  could detect the position of the transmitter  110  as well as the sensor states of the transmitter  110 . If no beacon signal is received during a first period, the transmitter  110  may enter a power saving mode. In this mode, the transmitter  110  detects the beacon signal every detection period. Once the beacon signal is detected, the transmitter  110  recovers back to normal working mode. The detection period is longer than the transmission period of the beacon signal. 
     Moreover, if no beacon signal is received during a second period in the power saving mode, the transmitter  110  may enter a sleep mode to turn off circuits and most parts until being waked up. In one embodiment of the present invention, in the sleep mode, the receiving circuit of the beacon signal and the transmitter of the electric signal of the transmitter  110  are turned off. A button or a switch of the transmitter  110  could be used to wake itself up by user. In another embodiment of the present application, examples shown in  FIGS. 23A, 23B, 24A and 24B  could be used to wake up the transmitter  110 . After the tip section  230  touches object, the voltage level of a connection port or GPIO1 is raised to high from low such that the transmitter  110  begins to transmit electric signals. 
     In the present application, one function of the ring electrode  550  is to receive the beacon signal in additional to the tip section  230 . Since the surface area and volume of the ring electrode  550  is larger than the top of the tip section  230 , it can receive the beacon signal distant away from the touch panel. Or the touch panel  120  may transmit weaker beacon signal to save power consumption. If no beacon signal is received for a while, active stylus may enter deeper sleep mode to save more power. When in this sleep mode, user may recover the transmitter  110  back to the normal working mode by pressing the tip section  230 . Examples shown in  FIGS. 23A, 23B, 24A and 24B  could be used to wake up the transmitter  110 . After the tip section  230  touches object, the voltage level of a connection port or GPIO1 is raised to high from low such that the transmitter  110  begins to transmit electric signals. 
     When multiple transmitters  110  operate on one touch panel  120 , the touch panel  120  could transmit different beacon signals for corresponding transmitter  110  to emit its electric signal. The transmitter  110  may adjust the signal frequency or modulation of the first signal source  211 , the second signal source  212 , and the third signal source  513  such that the touch panel  120  could distinguish the source transmitter  110  of the received electric signals. Analogously, the different beacon signals may have different frequencies or different modulations. 
     Please refer to  FIG. 22 , which illustrates a pressure sensor according to an embodiment of the present invention. In this embodiment, the control unit  2220  may feed driving signal with a frequency to an input terminal c of the pressure sensor  2210  and receive currents with current values I1 and I2 corresponding to a first capacitor C1 and a second capacitor C2, respectively. A ratio of these two current values is calculated by the control unit  2220 . Therefore a pressure level could be deduced accordingly. The control unit  2220  may embody the method shown in  FIG. 8 . In one application, the driving signal with the frequency is fed externally into the input terminal c of the pressure sensor  2220 . 
     Please refer to  FIGS. 23A and 23B , which depict profiling diagrams of a switch structure in accordance with an embodiment of the present invention. In the embodiment shown in  FIG. 23A , there are three circuit boards. As seen in previous figures, there is a ramp at the right hand side. Before the ramp pushes to left, a first contact point p1 of the upper circuit board is coupled to a voltage source Vdd and a first connection port (GPIO1). If no displacement vertical to the axis of the stylus, the first contact point p1 is contacted with a second contact point p2 on the middle circuit board. There is also a third contact point p3 on the middle circuit board coupled to the second contact point p2. A fourth contact point p4 of the lower circuit board is coupled to a ground level and a second connection port (GPIO2). Besides, the fourth contact point p4 is electrically coupled to the third contact point p3. There is a resistor between the power source Vdd and the first connection port (GPIO1). If the circuit between the upper and the middle circuit boards is shorted, i.e., the first contact point p1 contacts with the second contact point p2, and the circuit between the middle and lower circuit boards is shorted, i.e., the third contact point p3 contacts with the fourth contact point p4, the voltage level of the first connection port (GPIO1) is low or ground. 
     Please refer to  FIG. 23B , after the ramp is pressed, the movement of the ramp deforms the contacting parts of the upper and the lower circuit boards. Due to the deformations, the circuit between the upper and the middle circuit boards is open, i.e., the first contact point p1 separates with the second contact point p2, and the circuit between the middle and lower circuit boards is open, i.e., the third contact point p3 separates with the fourth contact point p4, the voltage level of the first connection port (GPIO1) is high or as high as Vdd. 
     In response to the voltage level of the first connection port (GPIO1) from low to high, the transmitter  110  in sleep mode is waked up. Already seen in previous figures, supporting elements corresponding to the upper and the lower circuit boards help to recover these two circuit boards&#39; position, respectively, if the pressure of the ramp disappears. At this moment, the voltage level of the first connection turns to low from high. The first and the second connection ports may be pins of processor in the transmitter  110 . 
     Please refer to  FIGS. 24A and 24B , which depict profiling diagrams of a switch structure in accordance with an embodiment of the present invention. The embodiment shown in  FIGS. 23A and 23B  has two potential openings. No matter which opening is open, it turns the voltage level of the first connection to high from low. However, the embodiment shown in  FIGS. 24A and 24B , only one potential opening is presented. The circuit along the middle circuit board connects to ground. In case the circuit between the upper and the middle circuit board is shorted, the voltage level of the first connection port is low or ground. Instead, if the circuit between the upper and the middle circuit board is open, the voltage level of the first connection port is high or as high as Vdd. In the embodiment shown in  FIGS. 24A and 24B , the second contact point p2 is electrically coupled to the second connection port (GPIO2). 
     Please refer to  FIG. 25 , which shows a diagram for calculating the tip position. There are two transmitters  110  shown in  FIG. 25 , both include the ring electrode  550  and the tip section  230 . The left-hand side transmitter  110  is perpendicular to the touch panel  120 , the angle is approaching or equals to 90 degree. The angle between the right-hand side transmitter  110  and the touch panel  120  is less than 90 degree. Moreover, a transparent surface layer of the touch panel  120  has a thickness. Normally, the transparent surface layer is a reinforced glass. A display layer is underneath the transparent surface layer. 
     Since the transmitters  110  emits electric signals via the ring electrode  550  and/or the tip section  230  during the time period R, the touch sensitive processing apparatus  130  could calculate a centroid position R_cg of the electric signals which is corresponding to a centroid position of the ring electrode  550  and/or the tip section  230  projecting to the touch panel  120 . After that, during the time periods T0 and T1, transmitter  110  emits electric signals only via the tip section  230 . Similarly, the touch sensitive processing apparatus  130  could calculate a centroid position Tip_cg of the electric signals which is corresponding to a centroid position of the tip section  230  projecting to the touch panel  120 . 
     For the left-hand side transmitter  110  shown in  FIG. 25 , since it is perpendicular to the touch panel  120 , the position R_cg equals or is approaching to the position Tip_cg. Thus, a position Tip_surface where top of the tip section  230  touches the transparent surface layer of the touch panel  120  equals or is approaching to the positions R_cg and Tip_cg. Moreover, a position Tip_display where the top of the tip section  230  projecting on the display layer of the touch panel  120  equals or is approaching to the positions, R_cg, Tip_cg, and Tip_surface. 
     For the right-hand side transmitter  110  shown in  FIG. 25 , there exist an inclination angle between the transmitter  110  and the touch panel  120 . More distant between the positions R_cg and Tip_cg, the inclination angle is larger. Depends on the implementations of the transmitter  110 , the inclination angle or positions Tip_surface or Tip_display could be found by the touch sensitive processing apparatus  130  via calculating or checking a look-up table according to the positions R_cg and Tip_cg. 
     Please refer to  FIG. 26 , which depicts a flow chart diagram for calculating the inclination angle in accordance with the present invention. The embodiment is applicable to the transmitter  110  having a ring electrode  550  shown in  FIG. 5 . It is also applicable to the signal modulations shown in  FIGS. 9E and 9F . The method could be performed by the touch sensitive processing apparatus  130  shown in  FIG. 1 . The embodiment shown in  FIG. 25  could be reference, too. 
     In step  2610 , calculating a first centroid position R_cg according to the ring electrode  550  and/or the tip section  230  projecting to the touch panel  120 . In step  2620 , calculating a second centroid position Tip_cg according to the tip section  230  projecting to the touch panel  120 . The present invention does not limit the executing order of these two steps  2610  and  2620 . Next, in optional step  2630 , calculating an inclination angle according to the first and the second centroid positions R_cg and Tip_cg. In optional step  2640 , calculating a position Tip_surface where top of the tip section  230  touches the transparent surface layer of the touch panel  120  according to the first and the second centroid positions R_cg and Tip_cg. In optional step  2650 , calculating a position Tip_display where the tip section  230  projecting on the display layer of the touch panel  120  according to the first and the second centroid positions R_cg and Tip_cg. Not all but at least one of steps  2630 ,  2640 , and  2650  has to be performed in the embodiment. And the present invention does not limit the executing order of these three steps  2630 ,  2640 , and  2650 . 
     Please refer to  FIG. 27 , which shows embodiments of how display interface reflects strobe according to the inclination angle and/or pressure of the tip section. There exists 5 rows of embodiments (a) through (e) shown in  FIG. 27 . Each row comprises three examples corresponding to three inclination angles. The examples of the most left column are corresponding to which the active stylus is perpendicular to the touch sensitive panel. The examples of the most right column are corresponding to an inclination angle larger than another inclination angle corresponding to the examples of the middle column. The so-called stroke in the present invention usually refers to a rendering area on the display by image processing software. 
     Please be noted that in the embodiment, it is not required to utilize the embodiment using the ring electrode to calculate the inclination angle and positions Tip_surface and Tip_display. In one embodiment, other forms of sensor may be installed on the active stylus to measure the inclination angle. For example, IMU, inertial measurement unit, gyroscope, and accelerometer made by microelectronics technology are configured to measure the inclination angle and report it and/or derived data to computer system comprising the touch sensitive panel via wired or wireless communication. Therefore the computer system could implement the embodiments shown in  FIG. 27 . The fore-mentioned wired or wireless communication may follow industrial or proprietary standards such as Bluetooth or Wireless USB etc. 
     Now assuming that active stylus touches the touch panel using the same pressure level in those embodiments shown in  FIG. 27 . In some embodiments, each intersection point of vertical and horizontal lines represents the positions Tip_surface corresponding to where top of the tip touches the transparent surface layer of the touch sensitive panel. In other embodiments, each intersection point of vertical and horizontal lines represents the positions Tip_cg corresponding to where the centroid of the tip. Of course, they may represent the locations Tip_display where the tip projecting the display layer of the touch sensitive panel. For convenience, those three positions are collectively named as a representative point, Tip. In other words, the representative point Tip may be one of the points, Tip_display, Tip_surface, or Tip_cg. 
     In the embodiment (a), in response to the increase of the inclination angle, the stroke shape changes from circle to ellipse. In other words, the distance between two focal points of the ellipse is corresponding to the inclination angle. The inclination angle increases with the distance between two focal points of the ellipse. Center of the ellipse is corresponding to the representative point Tip. 
     The difference between the embodiments (b) and (a) is that one intersection point of the semi-major axis and the ellipse is corresponding to the representative point Tip. The difference between the embodiments (c) and (a) is that one of the focal point of the ellipse is corresponding to the representative point Tip. The difference between the embodiments (d), (e), and (a) is that the stroke shape changes from ellipse to tear drop. Top of the tear drop of the embodiment (d) is corresponding to the representative point Tip. Somewhere from the top toward the end of the tear drop of the embodiment (e) is corresponding to the representative point Tip. 
     Although shown in  FIG. 27 , two stroke shapes and different points corresponding to the intersection point are enumerated. The present invention does not limit the stroke shape and the types of the representative point. In addition, in one embodiment, pressure of the tip may control the size of the shape. For example, the pressure may be corresponding to radius of circle or the distance between the focal points of the ellipse. In summarized, human-machine interface can change display content according to pressure of the tip and/or inclination angle of the active stylus. 
     In additional to change the stroke shape, the pressure of the tip and/or inclination angle of the stylus may be corresponding to different commands. For example of 3 dimensional design software, color temperature, strength, or scope of illuminating source could be changed according to the inclination angle. Or in case an object is selected by touch of the tip, orientation of the selected object could be changed according to direction of the inclination angle. Moreover, direction of the selected object could be rotated according to the inclination angle. 
     It is worthy noted that relation of the inclination angle and corresponding value is not limited as linearly in the present invention. In some embodiments, the relation may be non-linear and could be found in a lookup table or calculated in the quadratic function. 
     Please refer to  FIG. 28 , which depicts other embodiments of how display interface reflects strobe according to the inclination angle and/or pressure of the tip. It depicts two embodiments (a) and (b) which include left and right strokes, respectively. The inclination angle of the left hand side stroke is zero. The stroke includes five circles C1 through C5 with increasing radius. The inclination angle of the right hand side stroke is a non-zero constant. The stroke includes five ellipses E1 through E5 with increasing major and minor radius. Sizes of the ellipses E1 through E5 depends on pressure values of the tip which are as the same as corresponding circles C1 through C5. In addition, semi-major axes of these ellipses E1 through E5 are 30 degree off horizontal according to direction of the inclination angle. The direction of the inclination angle and the stroke direction are different. In this figure, these two directions are off a 15-degree angle. 
     The embodiment (a) shown in  FIG. 28  is corresponding to the embodiment (a) shown in  FIG. 27 , i.e., center of the ellipse is corresponding to the representative point Tip. Analogously, The embodiment (b) shown in  FIG. 28  is corresponding to the embodiment (b) shown in  FIG. 27 , i.e., the intersection point between the semi-major axis and the ellipse is corresponding to the representative point Tip. Could be seen in these two embodiments shown in  FIG. 28 , under the same pressure level, the stroke shapes are different according to different inclination angles. In consequence, strokes of some soft and flexible tips such as brush pen and quill pen could be simulated according to the pressure level and inclination angle. 
     One aspect of the present application is to provide a transmitter which comprises: a first component for receiving signal with a first frequency group, wherein a first impedance of the first component changes according to a pressure; a second component for receiving signal with a second frequency group, wherein the second component has a second impedance; and a tip section for receiving outputs of the first component and the second component and transmitting an electric signal, wherein the tip section is used to receive the pressure. 
     In one embodiment, the second impedance is not changed according to the pressure. Alternatively, the second impedance is changed according to the pressure, too. 
     In one embodiment, the transmitter further comprises a third switch and a third component serially connected to the third switch, wherein the first component is connected with the third switch and the third component in parallel. The transmitter may further comprise a fourth switch and a fourth component serially connected to the fourth switch, wherein the first component is connected with the fourth switch and the fourth component in parallel. 
     Alternatively, the transmitter further comprises a third switch and a third component serially connected to the third switch, wherein the second component is connected with the third switch and the third component in parallel. The transmitter may further comprise a fourth switch and a fourth component serially connected to the fourth switch, wherein the second component is connected with the fourth switch and the fourth component in parallel. 
     In one embodiment, the first frequency group comprises one or more first frequency, the second frequency group comprises one or more second frequency. The first frequency is different from the second frequency. 
     In one embodiment, the first impedance equals to the second impedance if the pressure is absent. In one embodiment, the tip section does not touch anything if the pressure is absent. 
     In one embodiment, a ratio of a first signal strength M1 corresponding to signal with the first frequency group and a second signal strength M2 corresponding to signal with the second frequency group is related to the pressure. The ratio is one of the followings: M1/M2, M2/M1, M1/(M1+M2), M2/(M1+M2), (M1−M2)/(M1+M2), and (M2−M1)/(M1+M2). 
     In one embodiment, if the ratio equals or falls into a first range, the pressure is absent. If the ratio equals or falls into a second range, the third switch is shorted and the first component is connected with the third component in parallel. If the ratio equals or falls into a third range, the fourth switch is shorted and the first component is connected with the fourth component in parallel. If the ratio equals or falls into a fourth range, the third switch and the fourth switch are shorted and the first component is connected with the third component and the fourth component in parallel. Alternatively, if the ratio equals or falls into a fifth range, the third switch is shorted and the second component is connected with the third component in parallel. If the ratio equals or falls into a sixth range, the fourth switch is shorted and the second component is connected with the fourth component in parallel. If the ratio equals or falls into a seventh range, the third switch and the fourth switch are shorted and the second component is connected with the third component and the fourth component in parallel. 
     In one embodiment, the first component is a force sensitive capacitor. The second component is a capacitor. 
     In one embodiment, the transmitter further comprises a ring electrode surrounding the tip section. The ring electrode is not electrically coupled to the tip section. In one embodiment, the ring electrode comprises one or more separate electrodes. 
     One aspect of the present application is to provide a transmitting method for a transmitter, which comprises a first component, a second component, and a tip section. The tip section is used to receive the outputs of the first and the second components. The method comprises changing a first impedance of the first component according to a pressure on the tip section; providing signal with a first frequency group to the first component; providing signal with a second frequency group to the second component; and transmitting an electric signal from the tip section. 
     One aspect of the present application is to provide a method for determining a pressure received by a transmitter, comprises: receiving an electric signal transmitted from the transmitter; calculating a first signal strength M1 corresponding to signal with a first frequency group contained in the electric signal; calculating a second signal strength M2 corresponding to signal with a second frequency group contained in the electric signal; calculating the pressure based on a ratio of the first signal strength M1 and the second signal strength M2. 
     In one embodiment, the step of calculating the pressure may comprises one of the followings: looking into a lookup table, linear interpolation, and quadratic curve interpolation 
     In one embodiment, the method further comprises determining the state of the third switch according to the ratio. Alternatively, the method further comprises determining the state of the fourth switch according to the ratio. 
     One aspect of the present application is to provide a touch sensitive processing apparatus for determining a pressure received by a transmitter, comprises: an interface configured to connects to a plurality of first electrodes and a plurality of second electrodes of a touch panel, wherein multiple sensing points are located where the intersections of the first and second electrodes; at least one demodulator for calculating a first signal strength M1 and a second signal strength M2 corresponding to signal with a first frequency group and signal with a second frequency group contained in the electric signal, respectively; and a calculating unit for calculating the pressure based on a ratio of the first signal strength M1 and the second signal strength M2. 
     In one embodiment, the calculating unit further determining the state of the third switch according to the ratio. Alternatively, the calculating unit further determining the state of the fourth switch according to the ratio. 
     One aspect of the present application is to provide a touch sensitive system for determining a pressure received by a transmitter, comprises: the transmitter, the touch panel; and a touch sensitive processing apparatus, the transmitter comprises: a first component for receiving signal with a first frequency group, wherein a first impedance of the first component changes according to a pressure; a second component for receiving signal with a second frequency group, wherein the second component has a second impedance; and a tip section for receiving outputs of the first component and the second component and transmitting an electric signal, wherein the tip section is used to receive the pressure. The touch panel comprises a plurality of first electrodes and a plurality of second electrodes, wherein multiple sensing points are located where the intersections of the first and second electrodes. The touch sensitive processing apparatus comprises: an interface configured to connects to the plurality of first electrodes and the plurality of second electrodes of the touch panel; at least one demodulator for calculating a first signal strength M1 and a second signal strength M2 corresponding to signal with a first frequency group and signal with a second frequency group contained in the electric signal, respectively; and a calculating unit for calculating the pressure based on a ratio of the first signal strength M1 and the second signal strength M2. 
     One aspect of the present application is to provide a transmitter, comprises: a first component for receiving a signal source, wherein a first impedance of the first component changes according to a pressure; a second component for receiving the signal source, wherein the second component has a second impedance; and a control unit for calculating a first current value I1 and a second current value I2 from the first component and the second component, respectively, and calculating the pressure according to a ratio of the first current value I1 and the second current value I2; and a communication unit for transmitting the pressure value. 
     In one embodiment, the second impedance is not changed according to the pressure. Alternatively, the second impedance is changed according to the pressure, too. 
     In one embodiment, the communication unit comprises a wireless communication unit for transmitting the pressure value. Alternatively, the communication unit comprises a wired communication unit for transmitting the pressure value. 
     In one embodiment, the signal source is the wired communication unit. In one embodiment, the signal source is a signal received from the tip section. 
     In one embodiment, the ratio is corresponding to the pressure. The ratio may be one of the followings: I1/I2, I2/I1, I1/(I1+I2), I2/(I1+I2), (I1−I2)/(I1+I2), and (I2−I1)/(I1+I2). 
     In one embodiment, the first impedance equals to the second impedance if the pressure is absent. 
     In one embodiment, the transmitter further comprises a third switch and a third component serially connected to the third switch, wherein the first component is connected with the third switch and the third component in parallel. The transmitter may further comprise a fourth switch and a fourth component serially connected to the fourth switch, wherein the first component is connected with the fourth switch and the fourth component in parallel. In one embodiment, if the ratio equals or falls into a first range, the pressure is absent. If the ratio equals or falls into a second range, the third switch is shorted and the first component is connected with the third component in parallel. If the ratio equals or falls into a third range, the fourth switch is shorted and the first component is connected with the fourth component in parallel. If the ratio equals or falls into a fourth range, the third switch and the fourth switch are shorted and the first component is connected with the third component and the fourth component in parallel. 
     Alternatively, the transmitter further comprises a third switch and a third component serially connected to the third switch, wherein the second component is connected with the third switch and the third component in parallel. The transmitter may further comprise a fourth switch and a fourth component serially connected to the fourth switch, wherein the second component is connected with the fourth switch and the fourth component in parallel. Alternatively, if the ratio equals or falls into a fifth range, the third switch is shorted and the second component is connected with the third component in parallel. If the ratio equals or falls into a sixth range, the fourth switch is shorted and the second component is connected with the fourth component in parallel. If the ratio equals or falls into a seventh range, the third switch and the fourth switch are shorted and the second component is connected with the third component and the fourth component in parallel. 
     In one embodiment, the control unit further determining the state of the third switch according to the ratio. Alternatively, the control unit further determining the state of the fourth switch according to the ratio. 
     In one embodiment, the communication unit further transmitting the state of the third switch. Alternatively, the communication unit further transmitting the state of the fourth switch. 
     One aspect of the present application is to provide a transmitting method for a transmitter, which comprises a first component, a second component, and a tip section. The tip section is used to receive the outputs of the first and the second components. The method comprises changing a first impedance of the first component according to a pressure on the tip section; providing a signal source to the first component and the second component; and calculating the pressure according to a ratio of the first current value I1 and the second current value I2; and transmitting the pressure value. 
     One aspect of the present application is to provide a touch sensitive system for determining a pressure received by a transmitter, comprises: the transmitter; and a host. The transmitter comprises: a first component for receiving a signal source, wherein a first impedance of the first component changes according to a pressure; a second component for receiving the signal source, wherein the second component has a second impedance; and a control unit for calculating a first current value I1 and a second current value I2 from the first component and the second component, respectively, and calculating the pressure according to a ratio of the first current value I1 and the second current value I2; and a communication unit for transmitting the pressure value to the host. The host comprises a host communication unit for receiving the pressure value. 
     In one embodiment, the touch sensitive system further comprises a touch panel and a touch sensitive processing apparatus, wherein the touch sensitive processing apparatus coupled to the touch panel is configured to detect a position the transmitter is relative to the touch panel and to send the position to the host. 
     In one embodiment, the control unit further determining the state of the third switch according to the ratio. Alternatively, the control unit further determining the state of the fourth switch according to the ratio. In one embodiment, the communication unit further transmitting the state of the third switch to the host. Alternatively, the communication unit further transmitting the state of the fourth switch to the host. In one embodiment, the host communication unit is configured to receive the state of the third switch. Alternatively, the host communication unit is configured to receive the state of the fourth switch. 
     One aspect of the present application is to provide a force sensor, comprises a first input terminal for receiving signal with a first frequency group; a second input terminal for receiving signal with a second frequency group; and an output terminal for transmitting an electric signal, wherein a ratio of a first signal strength M1 and a second signal strength M2 corresponding to signal with a first frequency group and signal with a second frequency group contained in the electric signal, respectively, is corresponding to a pressure. 
     In one embodiment, the ratio is one of the followings: M1/M2, M2/M1, M1/(M1+M2), M2/(M1+M2), (M1−M2)/(M1+M2), and (M2−M1)/(M1+M2). 
     In one embodiment, the force sensor further comprises a third switch. In one embodiment, if the ratio equals or falls into a first range, the pressure is absent. If the ratio equals or falls into a second range, the third switch is shorted. 
     Alternatively, the force sensor further comprises a fourth switch. In one embodiment, if the ratio equals or falls into a third range, the fourth switch is shorted. If the ratio equals or falls into a fourth range, the third switch and the fourth switch are shorted. 
     One aspect of the present application is to provide a force sensor, comprises a first output terminal for outputting signal with a first current value I1; and a second output terminal for outputting signal with a second current value I2, wherein a ratio of the first current value I1 and the second current value I2 is corresponding to a pressure. 
     In one embodiment, the ratio may be one of the followings: I1/I2, I2/I1, I1/(I1+I2), I2/(I1+I2), (I1−I2)/(I1+I2), and (I2−I1)/(I1+I2). 
     In one embodiment, the force sensor further comprises a third switch. In one embodiment, if the ratio equals or falls into a first range, the pressure is absent. If the ratio equals or falls into a second range, the third switch is shorted. 
     Alternatively, the force sensor further comprises a fourth switch. In one embodiment, if the ratio equals or falls into a third range, the fourth switch is shorted. If the ratio equals or falls into a fourth range, the third switch and the fourth switch are shorted. 
     One aspect of the present application is to provide a force sensor, comprises: a first circuit board containing a first metal plate for receiving signal with a first frequency group; a second circuit board in parallel with the first circuit board, containing a second metal plate and a third metal plate which are intact, wherein the third metal plate for receiving signal with a second frequency group, whether the second metal plate for outputting an electric signal, wherein the second metal plate is in the middle of the first and the third metal plates; and a ramp means for bending the first circuit board upward. 
     One aspect of the present application is to provide a force sensor, comprises: a first circuit board containing a first metal plate for outputting signal with a first current value I1; a second circuit board in parallel with the first circuit board, containing a second metal plate and a third metal plate which are intact to each other, wherein the third metal plate for outputting signal with a second current value I2, whether the second metal plate for receiving a signal source, wherein the second metal plate is in the middle of the first and the third metal plates; and a ramp means for bending the first circuit board upward. 
     In one embodiment, part of the first metal plate is located in the bent part of the first circuit board. 
     In one embodiment, the force sensor further comprises a supporting element for supporting the first circuit board. 
     In one embodiment, the first metal plate, the second metal plate, and the third metal plate are in parallel. Alternatively, the distance between the first and the second metal plate equals to the distance between the second metal plate and the third metal plate. 
     In one embodiment, a first capacitor is formed by the first and the second metal plates; a second capacitor is formed by the second and the third metal plates. Alternatively, the impedance of the first capacitor equals to the impedance of the second capacitor if the first circuit board is not bending. 
     In one embodiment, both the first and the second circuit boards are printed circuit boards. 
     One aspect of the application is to provide a force sensor, comprises a first circuit board containing a first metal plate and a third metal plate which are intact to each other for receiving signal with a first frequency group and signal with a second frequency group, respectively; a second circuit board in parallel with the first circuit board containing a second metal plate for outputting an electric signal; and a ramp means for bending the first circuit board upward. 
     One aspect of the application is to provide a force sensor, comprises a first circuit board containing a first metal plate and a third metal plate which are intact to each other for outputting signal with a first current value and signal with a second current value, respectively, a second circuit board in parallel with the first circuit board containing a second metal plate for receiving a signal source  1 ; and a ramp means for bending the first circuit board upward. 
     In one embodiment, the force sensor further comprises a supporting element for supporting the first circuit board. 
     In one embodiment, the first metal plate is in parallel with the second metal plate; the second metal plate is in parallel with the third metal plate. Alternatively, the distance between the first and the second metal plate equals to the distance between the second metal plate and the third metal plate. 
     In one embodiment, a first capacitor is formed by the first and the second metal plates; a second capacitor is formed by the second and the third metal plates. Alternatively, the impedance of the first capacitor equals to the impedance of the second capacitor if the first circuit board is not bending. 
     In one embodiment, both the first and the second circuit boards are printed circuit boards. 
     One aspect of the application is to provide a force sensor, comprises a first circuit board containing a first metal plate and a third metal plate which are intact to each other for receiving signal with a first frequency group and signal with a second frequency group, respectively; a second circuit board in parallel with the first circuit board containing a second metal plate for outputting an electric signal; a third circuit board containing a fourth metal plate and a fifth metal plate which are intact to each other for receiving signal with the first frequency group and signal with the second frequency group, respectively; and a ramp means for bending the first circuit board upward and bending the third circuit board downward. 
     In one embodiment, the force sensor further comprises a first supporting element for supporting the first circuit board. In one embodiment, the force sensor further comprises a second supporting element for supporting the third circuit board. 
     In one embodiment, the first metal plate is in parallel with the second metal plate; the second metal plate is in parallel with the third metal plate; the fourth metal plate is in parallel with the second metal plate; the fifth metal plate is in parallel with the second metal plate. Alternatively, the distance between the first and the second metal plate equals to the distance between the second metal plate and the third metal plate. The distance between the fourth and the second metal plate equals to the distance between the second metal plate and the fifth metal plate. 
     In one embodiment, the first metal plate is on top of the fourth metal plate. Alternatively, the third metal plate is on top of the fifth metal plate. 
     In one embodiment, area of the first metal plate equals to area of the fourth metal plate. Alternatively, area of the third metal plate equals to area of the fifth metal plate. 
     In one embodiment, a first capacitor is formed by the first and the second metal plates; a second capacitor is formed by the second and the third metal plates; a third capacitor is formed by the fourth and the second metal plates; a fourth capacitor is formed by the second and the fifth metal plates. Alternatively, the impedance of the first capacitor equals to the impedance of the second capacitor if the first circuit board is not bending. Alternatively, the impedance of the third capacitor equals to the impedance of the fourth capacitor if the third circuit board is not bending. Alternatively, the impedance of the first capacitor equals to the impedance of the third capacitor, the impedance of the second capacitor equals to the impedance of the fourth capacitor. 
     In one embodiment, the first, the second, and the third circuit boards are all printed circuit boards. 
     One aspect of the application is to provide a force sensor, comprises a first circuit board containing a first metal plate for receiving signal with a first frequency group; a second circuit board in parallel with the first circuit board containing a second metal plate, a third metal plate, a fourth metal plate and a fifth metal plate which are intact and parallel to each other, wherein the third metal plate and the fourth metal plate for receiving signal with a second frequency group, wherein the second metal plate is coupled to the fifth metal plate for outputting an electric signal; a third circuit board containing a sixth metal plate for receiving signal with the first frequency board, wherein the second circuit board is placed in between the first and the third circuit boards; and a ramp means for bending the first circuit board upward and bending the third circuit board downward. 
     In one embodiment, the force sensor further comprises a first supporting element for supporting the first circuit board. In one embodiment, the force sensor further comprises a second supporting element for supporting the third circuit board. 
     In one embodiment, the first metal plate is in parallel with the second metal plate; the second metal plate is in parallel with the third metal plate; the third metal plate is in parallel with the fourth metal plate; the fourth metal plate is in parallel with the fifth metal plate; and the fifth metal plate is in parallel with the six metal plate. Alternatively, the distance between the first and the second metal plate equals to the distance between the second metal plate and the third metal plate. The distance between the fourth and the fifth metal plate equals to the distance between the fifth metal plate and the sixth metal plate. 
     In one embodiment, the first metal plate is on top of the sixth metal plate. 
     In one embodiment, area of the first metal plate equals to area of the sixth metal plate. Alternatively, area of the second metal plate is on top of the fifth metal plate. Alternatively, area of the third metal plate is on top of the fourth metal plate. 
     In one embodiment, a first capacitor is formed by the first and the second metal plates; a second capacitor is formed by the second and the third metal plates; a third capacitor is formed by the fourth and the fifth metal plates; a fourth capacitor is formed by the fifth and the sixth metal plates. Alternatively, the impedance of the first capacitor equals to the impedance of the second capacitor if the first circuit board is not bending. Alternatively, the impedance of the third capacitor equals to the impedance of the fourth capacitor if the third circuit board is not bending. Alternatively, the impedance of the first capacitor equals to the impedance of the fourth capacitor, the impedance of the second capacitor equals to the impedance of the third capacitor. 
     In one embodiment, the first, the second, and the third circuit boards are all printed circuit boards. 
     One aspect of the application is to provide a force sensor, comprises: a first metal plate, a second metal plate, and third metal plate which are intact and sequentially parallel to each other, wherein the first metal plate for receiving signal with a first frequency group, the third metal plate for receiving signal with a second frequency group, the second metal plate for outputting an electric signal, wherein one end of the second metal plate is bendable. 
     One aspect of the application is to provide a force sensor, comprises: a first metal plate, a second metal plate, and third metal plate which are intact and sequentially parallel to each other, wherein the first metal plate for outputting signal with a first current value, the third metal plate for outputting signal with a second current value, and the second metal plate for receiving a signal source, wherein one end of the second metal plate is bendable. 
     In one embodiment, the distance between the first metal plate and the second metal plate equals to the distance between the second metal plate and the third metal plate. 
     In one embodiment, a first capacitor is formed by the first and the second metal plates; a second capacitor is formed by the second and the third metal plates. Alternatively, the impedance of the first capacitor equals to the impedance of the second capacitor if the first circuit board is not bending. 
     One aspect of the application is to provide a force sensor, comprises: a first metal plate, a second metal plate, and third metal plate which are intact and sequentially parallel to each other, wherein the first metal plate for outputting an electric signal, the second metal plate for receiving signal with a first frequency group, the third metal plate for receiving signal with a second frequency group, wherein one end of the first metal plate is bendable. 
     One aspect of the application is to provide a force sensor, comprises: a first metal plate, a second metal plate, and third metal plate which are intact and sequentially parallel to each other, wherein the first metal plate for receiving a signal source, the second metal plate for outputting signal with a first current value, the third metal plate for outputting signal with a second current value, wherein one end of the first metal plate is bendable. 
     In one embodiment, the distance between the first metal plate and the second metal plate equals to the distance between the second metal plate and the third metal plate. 
     In one embodiment, a first capacitor is formed by the first and the second metal plates; a second capacitor is formed by the second and the third metal plates. Alternatively, the impedance of the first capacitor equals to the impedance of the second capacitor if the first circuit board is not bending. 
     One aspect of the application is to provide a transmitter, comprises a moving part for moving a stroke along an axis of the transmitter; an dielectric material placing in the rear of the moving part; and a conductor placing in the rear of the dielectric material, wherein a force sensitive capacitor is formed by the moving part, the dielectric, and the conductor. 
     In one embodiment, the transmitter further comprises a tip section placing in the fore of the moving part. In one embodiment, the tip section is a conductor coupling to the moving part. Alternatively, the tip section is configured to transmit an electric signal. 
     In one embodiment, the transmitter further comprises an elastic element and a shell component, wherein the elastic element is configured to provide elastic force between the moving part and the shell component such that the moving part is pushed to the fore end of the stroke by the elastic force. 
     In one embodiment, the dielectric material is a dielectric film. The conductor comprises a compressible conductor and a conductor base. Alternatively, the dielectric material is compressible dielectric material. 
     In one embodiment, a contact surface of the dielectric material facing the conductor comprises one of the following: a sloped surface, a surface with multiple bulges, a conical surface, and a surface with central bulge. Alternatively, a contact surface of the conductor facing the dielectric material comprises one of the following: a sloped surface, a surface with multiple bulges, a conical surface, and a surface with central bulge. 
     In one embodiment, the dielectric material and the conductor reside in an internal chamber of the shell component. Alternatively, the internal chamber is an empty cylinder. 
     In one embodiment, the moving part comprises a fore moving part and a rear moving part. The fore moving part contacts with the tip section and electrically couples to the tip section. 
     In one embodiment, the transmitter further comprises a circuit board which connects to the conductor via a base wire and connects to the moving part via a moving part wire. Alternatively, the moving part wire is coupled to the elastic element. 
     In one embodiment, the elastic element does not surround the moving part. Alternatively, the base wire does not surround the conductor. 
     One aspect of the application is to provide a circuit switch, comprises: a first circuit board, a second circuit board, a third circuit board which are intact and sequentially parallel to each other, and a dual ramp means, wherein a first end of the first circuit board and a first end of the third circuit board contacts with the two ramps of the dual ramp means, respectively, a first end of the second circuit board does not contact with the dual ramp means, the first end of the second circuit board comprises a circuit, a second point and a third point of the circuit contacts with and electrically couples to a first point of the first circuit board and a fourth point of the third circuit board, respectively. 
     In one embodiment, when the dual ramp means moves toward the second circuit board, the first circuit board and the third circuit board pressed by the dual ramp means and bent upward and downward, respectively, whereby the electrically coupling between the first point and the second point is open and the electrically coupling between the third point and the fourth point is open, the voltage level of the first connection port is high. 
     In one embodiment, the first point is connected with a first connection point and a high voltage in parallel, the fourth point is connected with a low voltage, the voltage level of the first connection point is low if the first point and the second point are shorted and the third point and the fourth point are shorted, the voltage level of the first connection point is high if the electrically coupling between the first point and the second point is open or the electrically coupling between the third point and the fourth point is open. 
     In one embodiment, the dual ramp means connects with a tip section. 
     In one embodiment, the circuit is placed at the edge of the first end of the second circuit board. 
     One aspect of the application is to provide a circuit switch, comprises: a first circuit board, a second circuit board, a third circuit board which are intact and sequentially parallel to each other, and a dual ramp means, wherein a first end of the first circuit board and a first end of the third circuit board contacts with the two ramps of the dual ramp means, respectively, a first end of the second circuit board does not contact with the dual ramp means, the first end of the second circuit board comprises a circuit, a second point of the circuit contacts with and electrically couples to a first point of the first circuit board. 
     In one embodiment, when the dual ramp means moves toward the second circuit board, the first circuit board and the third circuit board pressed by the dual ramp means and bent upward and downward, respectively, whereby the electrically coupling between the first point and the second point is open. 
     In one embodiment, the first point is connected with a first connection point and a high voltage, the second point is connected with a low voltage, the voltage level of the first connection point is low if the first point and the second point are shorted, the voltage level of the first connection point is high if the electrically coupling between the first point and the second point is open. 
     In one embodiment, the dual ramp means connects with a tip section. 
     In one embodiment, the circuit is placed at the edge of the first end of the second circuit board. 
     One aspect of the application is to provide a stylus, comprises: a control unit, a tip section; and a circuit switch, which comprises: a first circuit board, a second circuit board, a third circuit board which are intact and sequentially parallel to each other, and a dual ramp means, wherein a first end of the first circuit board and a first end of the third circuit board contacts with the two ramps of the dual ramp means, respectively, a first end of the second circuit board does not contact with the dual ramp means, the first end of the second circuit board comprises a circuit, a second point and a third point of the circuit contacts with and electrically couples to a first point of the first circuit board and a fourth point of the third circuit board, respectively, wherein the first point connects with a first connection point of the control unit and a high voltage in parallel, the fourth point is connected with a low voltage, the voltage of the first connection port is low. 
     In one embodiment, when the dual ramp means moves toward the second circuit board, the first circuit board and the third circuit board pressed by the dual ramp means and bent upward and downward, respectively, whereby the electrically coupling between the first point and the second point is open and the electrically coupling between the third point and the fourth point is open, the voltage level of the first connection port is high. 
     In one embodiment, the control unit is waked up if the voltage level of the first connection port turns high from low. 
     One aspect of the application is to provide a stylus, comprises: a control unit, a tip section; and a circuit switch, which comprises: a first circuit board, a second circuit board, a third circuit board which are intact and sequentially parallel to each other, and a dual ramp means, wherein a first end of the first circuit board and a first end of the third circuit board contacts with the two ramps of the dual ramp means, respectively, a first end of the second circuit board does not contact with the dual ramp means, the first end of the second circuit board comprises a circuit, a second point of the circuit contacts with and electrically couples to a first point of the first circuit board, wherein the first point connects with a first connection point of the control unit and a high voltage in parallel, the second point is connected with a low voltage, the voltage of the first connection port is low. 
     In one embodiment, when the dual ramp means moves toward the second circuit board, the first circuit board and the third circuit board pressed by the dual ramp means and bent upward and downward, respectively, whereby the electrically coupling between the first point and the second point is open, the voltage level of the first connection port is high. 
     In one embodiment, the control unit is waked up if the voltage level of the first connection port turns high from low. 
     One aspect of the application is to provide a method for a transmitter, comprises: transmitting a first period electric signal during a first time period; and transmitting a second period electric signal during a second time period, wherein frequency group contained in the first period electric signal is different from frequency group contained in the second period electric signal. 
     One aspect of the application is to provide a transmitter, which is configured for transmitting a first period electric signal during a first time period; and transmitting a second period electric signal during a second time period, wherein frequency group contained in the first period electric signal is different from frequency group contained in the second period electric signal. 
     One aspect of the application is to provide a touch sensitive system, comprises a transmitter, a touch panel and a touch sensitive processing apparatus coupled to the touch panel, which is configured for detecting the transmitter according to a first period electric signal and a second period electric signal. The transmitter is configured for transmitting the first period electric signal during a first time period; and transmitting the second period electric signal during a second time period, wherein frequency group contained in the first period electric signal is different from frequency group contained in the second period electric signal. 
     In one embodiment, the frequency group contains one or more frequencies. 
     In one embodiment, the first time period is after a beacon signal detected by the transmitter. Alternatively, there exists a first delay time between the beacon signal detection and the first time period. 
     In one embodiment, there exists a second delay time between the first time period and the second time period. 
     In one embodiment, there exists a third delay time after the second time period. 
     In one embodiment, prior to the detection of the beacon signal, the transmitter detects an interference signal. Alternatively, the interference signal comprises signals which are coherent to the first period electric signal and the second electric signal. 
     Please refer to the Table 1, in one embodiment, if a tip section of the transmitter does not touch, a first signal source and a second signal source of the transmitter simultaneously transmit signals with the same frequency group. 
     Please refer to the Table 1, in one embodiment, if the tip section of the transmitter does not touch and a first switch of the transmitter is open, the first signal source and the second signal source simultaneously transmit signals with a first frequency group; if the tip section does not touch and the first switch is shorted, the first signal source and the second signal source simultaneously transmit signals with a second frequency group, the first frequency group is different to the second frequency group. 
     Please refer to the Table 1, in one embodiment, if the tip section of the transmitter does not touch and a second switch of the transmitter is open, the first signal source and the second signal source simultaneously transmit signals with the first frequency group; if the tip section does not touch and the first switch is shorted, the first signal source and the second signal source simultaneously transmit signals with a third frequency group, the first frequency group is different to the third frequency group. 
     Please refer to the Table 2, in one embodiment, if a tip section of the transmitter does touch, a first signal source and a second signal source of the transmitter transmit signals with different frequency groups during the second time period and the first time period. 
     Please refer to the Table 2, in one embodiment, if the tip section of the transmitter does touch and a first switch of the transmitter is open, the second signal source transmits signal with a first frequency group during the first time period; if a tip section of the transmitter does touch and the first switch of the transmitter is shorted, the second signal source transmits signal with a second frequency group during the first time period, the first frequency group is different to the second frequency group. 
     Please refer to the Table 2, in one embodiment, if the tip section of the transmitter does touch and a second switch of the transmitter is open, the first signal source transmits signal with a third frequency group during the second time period; if a tip section of the transmitter does touch and the second switch of the transmitter is shorted, the first signal source transmits signal with the second frequency group during the second time period, the third frequency group is different to the second frequency group. 
     In one embodiment, a ratio of a first signal strength M1 transmitted by the first signal source during the second time period and a second signal strength M2 transmitted by the second signal source during the first time period is corresponding to a pressure on the transmitter. 
     In one embodiment, a ring electrode transmits a zeroth period electric signal during a zeroth time period, the zeroth time period is after the transmitter detects the beacon signal. Alternatively, there exists a zeroth delay time between the detection of the beacon signal and the zeroth time period. 
     In one embodiment, the ring electrode does not transmit electric signal during the first time period and the second time period. 
     In one embodiment, frequency group contained in the zeroth period electric signal is different to frequency group contained the first period electric signal and the second period electric signal. 
     One aspect of the application is to provide a method for a transmitter, comprises: transmitting a first period electric signal during a first time period; and transmitting a second period electric signal during a second time period, wherein frequency group contained in the first period electric signal is as the same as frequency group contained in the second period electric signal. 
     One aspect of the application is to provide a transmitter, which is configured for transmitting a first period electric signal during a first time period; and transmitting a second period electric signal during a second time period, wherein frequency group contained in the first period electric signal is as the same as frequency group contained in the second period electric signal. 
     One aspect of the application is to provide a touch sensitive system, comprises a transmitter, a touch panel and a touch sensitive processing apparatus coupled to the touch panel, which is configured for detecting the transmitter according to a first period electric signal and a second period electric signal. The transmitter is configured for transmitting the first period electric signal during a first time period; and transmitting the second period electric signal during a second time period, wherein frequency group contained in the first period electric signal is as the same as frequency group contained in the second period electric signal. 
     In one embodiment, the frequency group contains one or more frequencies. 
     In one embodiment, the first time period is after a beacon signal detected by the transmitter. Alternatively, there exists a first delay time between the beacon signal detection and the first time period. 
     In one embodiment, there exists a second delay time between the first time period and the second time period. 
     In one embodiment, there exists a third delay time after the second time period. 
     In one embodiment, prior to the detection of the beacon signal, the transmitter detects an interference signal. Alternatively, the interference signal comprises signals which are coherent to the first period electric signal and the second electric signal. 
     Please refer to the Table 3, in one embodiment, if a tip section of the transmitter does not touch, a first signal source and a second signal source of the transmitter simultaneously transmit signals with the same frequency group. 
     Please refer to the Table 3, in one embodiment, if the tip section of the transmitter does not touch and a first switch of the transmitter is open, the first signal source and the second signal source simultaneously transmit signals with a first frequency group; if the tip section does not touch and the first switch is shorted, the first signal source and the second signal source simultaneously transmit signals with a second frequency group, the first frequency group is different to the second frequency group. 
     Please refer to the Table 3, in one embodiment, if the tip section of the transmitter does not touch and a second switch of the transmitter is open, the first signal source and the second signal source simultaneously transmit signals with the first frequency group; if the tip section does not touch and the first switch is shorted, the first signal source and the second signal source simultaneously transmit signals with a third frequency group, the first frequency group is different to the third frequency group. 
     Please refer to the Table 4, in one embodiment, if a tip section of the transmitter does touch, a first signal source and a second signal source of the transmitter transmit signals with the same frequency groups during the second time period and the first time period, respectively. 
     Please refer to the Table 4, in one embodiment, if a tip section of the transmitter does touch and a first switch of the transmitter is open, the second signal source transmits signal with a first frequency group during the first time period; if a tip section of the transmitter does touch and the first switch of the transmitter is shorted, the second signal source transmits signal with a second frequency group during the first time period, the first frequency group is different to the second frequency group. 
     Please refer to the Table 4, in one embodiment, if the tip section of the transmitter does touch and a second switch of the transmitter is open, the first signal source transmits signal with a third frequency group during the second time period; if a tip section of the transmitter does touch and the second switch of the transmitter is shorted, the first signal source transmits signal with the second frequency group during the second time period, the third frequency group is different to the second frequency group. 
     In one embodiment, a ring electrode transmits a zeroth period electric signal during a zeroth time period, the zeroth time period is after the transmitter detects the beacon signal. Alternatively, there exists a zeroth delay time between the detection of the beacon signal and the zeroth time period. 
     In one embodiment, the ring electrode does not transmit electric signal during the first time period and the second time period. 
     In one embodiment, frequency group contained in the zeroth period electric signal is different to frequency group contained the first period electric signal and the second period electric signal. 
     In one embodiment, a ratio of a first signal strength M1 transmitted by the first signal source during the second time period and a second signal strength M2 transmitted by the second signal source during the first time period is corresponding to a pressure on the transmitter. 
     One aspect of the application is to provide a method for detecting a transmitter, comprises: detecting a first period electric signal emitted from the transmitter during a first time period; and detecting a second period electric signal emitted from the transmitter from a second time period, wherein frequency group contained in the first period electric signal is different from frequency group contained in the second period electric signal. 
     One aspect of the application is to provide a touch sensitive processing apparatus for detecting a transmitter, coupled to a touch panel which comprises a plurality of first electrodes and a plurality of second electrodes as well as multiple sensing points located where the intersections, the touch sensitive processing apparatus is configured for detecting a first period electric signal emitted from the transmitter during a first time period; and detecting a second period electric signal emitted from the transmitter from a second time period, wherein frequency group contained in the first period electric signal is different from frequency group contained in the second period electric signal. 
     One aspect of the application is to provide a touch sensitive system comprises a transmitter, a touch panel, and a touch sensitive processing apparatus, coupled to the touch panel, configured for detecting a first period electric signal emitted from the transmitter during a first time period; and detecting a second period electric signal emitted from the transmitter from a second time period, wherein frequency group contained in the first period electric signal is different from frequency group contained in the second period electric signal. 
     In one embodiment, the frequency group contains one or more frequencies. 
     In one embodiment, the first time period is after a beacon signal detected by the transmitter. Alternatively, there exists a first delay time between the beacon signal detection and the first time period. 
     In one embodiment, there exists a second delay time between the first time period and the second time period. 
     In one embodiment, there exists a third delay time after the second time period. 
     In one embodiment, prior to the detection of the beacon signal, the transmitter detects an interference signal. In one embodiment, an interference signal is detected after the first time period. In one embodiment, an interference signal is detected after the second time period. Alternatively, the interference signal comprises signals which are coherent to the first period electric signal and the second electric signal. 
     Please refer to the Table 1, in one embodiment, if the transmitter simultaneously transmit signals with the same frequency group, it is determined that a tip section of the transmitter does not touch. 
     Please refer to the Table 1, in one embodiment, if the transmitter transmits signals with a first frequency group during a first time period, it is determined that the tip section does not touch and a first switch of the transmitter is open; if the transmitter transmits signals with a second frequency group during the first time period, it is determined that the tip section does not touch and the first switch of the transmitter is shorted, wherein the first frequency group is different to the second frequency group. 
     Please refer to the Table 1, in one embodiment, if the transmitter transmits signals with a first frequency group during a second time period, it is determined that the tip section does not touch and a second switch of the transmitter is open; if the transmitter transmits signals with a third frequency group during the second time period, it is determined that the tip section does not touch and the first switch of the transmitter is shorted, wherein the first frequency group is different to the third frequency group. 
     Please refer to the Table 2, in one embodiment, if the transmitter transmits signals with different frequency groups during the first time period and the second time period, it is determined that a tip section of the transmitter does touch. 
     Please refer to the Table 2, in one embodiment, if the transmitter transmits signal with a first frequency group during the first time period, it is determined that the tip section does touch and a first switch of the transmitter is open; if the transmitter transmits signal with a second frequency group during the first time period, it is determined that the tip section does touch and the first switch of the transmitter is shorted, wherein the first frequency group is different to the third frequency group. 
     Please refer to the Table 2, in one embodiment, if the transmitter transmits signal with a third frequency group during the second time period, it is determined that the tip section does touch and a second switch of the transmitter is open; if the transmitter transmits signal with a second frequency group during the second time period, it is determined that the tip section does touch and the second switch of the transmitter is shorted, wherein the first frequency group is different to the third frequency group. 
     In one embodiment, a ratio of a first signal strength M1 transmitted by the first signal source during the second time period and a second signal strength M2 transmitted by the second signal source during the first time period is calculated; and a pressure on the transmitter according to the ratio is calculated. 
     In one embodiment, detecting a zeroth period electric signal transmitted by the transmitter during a zeroth time period, the zeroth time period is after the transmitter detects the beacon signal. Alternatively, there exists a zeroth delay time between the detection of the beacon signal and the zeroth time period. 
     In one embodiment, frequency group contained in the zeroth period electric signal is different to frequency group contained the first period electric signal and the second period electric signal. 
     One aspect of the application is to provide a method for detecting a transmitter, comprises: detecting a first period electric signal emitted from the transmitter during a first time period; and detecting a second period electric signal emitted from the transmitter from a second time period, wherein frequency group contained in the first period electric signal is as the same as frequency group contained in the second period electric signal. 
     One aspect of the application is to provide a touch sensitive processing apparatus for detecting a transmitter, coupled to a touch panel which comprises a plurality of first electrodes and a plurality of second electrodes as well as multiple sensing points located where the intersections, the touch sensitive processing apparatus is configured for detecting a first period electric signal emitted from the transmitter during a first time period; and detecting a second period electric signal emitted from the transmitter from a second time period, wherein frequency group contained in the first period electric signal is as the same as frequency group contained in the second period electric signal. 
     One aspect of the application is to provide a touch sensitive system comprises a transmitter, a touch panel, and a touch sensitive processing apparatus, coupled to the touch panel, configured for detecting a first period electric signal emitted from the transmitter during a first time period; and detecting a second period electric signal emitted from the transmitter from a second time period, wherein frequency group contained in the first period electric signal is as the same as frequency group contained in the second period electric signal. 
     In one embodiment, the frequency group contains one or more frequencies. 
     In one embodiment, the first time period is after a beacon signal detected by the transmitter. Alternatively, there exists a first delay time between the beacon signal detection and the first time period. 
     In one embodiment, there exists a second delay time between the first time period and the second time period. 
     In one embodiment, there exists a third delay time after the second time period. 
     In one embodiment, prior to the detection of the beacon signal, the transmitter detects an interference signal. In one embodiment, an interference signal is detected after the first time period. In one embodiment, an interference signal is detected after the second time period. Alternatively, the interference signal comprises signals which are coherent to the first period electric signal and the second electric signal. 
     Please refer to the Table 3, in one embodiment, if the first period electric signals with the same frequency group and the second period electric signals with the same frequency group, it is determined that a tip section of the transmitter does not touch. 
     Please refer to the Table 3, in one embodiment, if the transmitter transmits signals with a first frequency group, it is determined that the tip section does not touch and a first switch of the transmitter is open; if the transmitter transmits signals with a second frequency group, it is determined that the tip section does not touch and the first switch of the transmitter is shorted, wherein the first frequency group is different to the second frequency group. 
     Please refer to the Table 3, in one embodiment, if the transmitter transmits signals with a first frequency group, it is determined that the tip section does not touch and a second switch of the transmitter is open; if the transmitter transmits signals with a third frequency group, it is determined that the tip section does not touch and the first switch of the transmitter is shorted, wherein the first frequency group is different to the third frequency group. 
     Please refer to the Table 4, in one embodiment, if the first period electric signals with the same frequency group and the second period electric signals with the same frequency group and a ratio of a signal strength M1 of the first period electric signal and a signal strength M2 of the second period electric signal does not fall into a first range, it is determined that a tip section of the transmitter does not touch. 
     Please refer to the Table 4, in one embodiment, if the transmitter transmits signal with a first frequency group during the first time period and the ratio does not fall into a first range, it is determined that the tip section does touch and a first switch of the transmitter is open; if the transmitter transmits signal with a second frequency group during the first time period and the ratio does not fall into the first range, it is determined that the tip section does touch and the first switch of the transmitter is shorted, wherein the first frequency group is different to the third frequency group. 
     Please refer to the Table 4, in one embodiment, if the transmitter transmits signal with a third frequency group during the second time period and the ratio does not fall into a first range, it is determined that the tip section does touch and a first switch of the transmitter is open; if the transmitter transmits signal with a second frequency group during the second time period and the ratio does not fall into the first range, it is determined that the tip section does touch and the second switch of the transmitter is shorted, wherein the first frequency group is different to the third frequency group. 
     In one embodiment, a ratio of a first signal strength M1 transmitted by the first signal source during the second time period and a second signal strength M2 transmitted by the second signal source during the first time period is calculated; and a pressure on the transmitter according to the ratio is calculated. 
     In one embodiment, detecting a zeroth period electric signal transmitted by the transmitter during a zeroth time period, the zeroth time period is after the transmitter detects the beacon signal. Alternatively, there exists a zeroth delay time between the detection of the beacon signal and the zeroth time period. 
     In one embodiment, frequency group contained in the zeroth period electric signal is as the same as frequency group contained the first period electric signal and the second period electric signal. 
     One aspect of the present application is to provide a transmitter, comprises: a tip section and a ring electrode surrounding the tip section, wherein the tip section is not electric coupling to the ring electrode. 
     In one embodiment, the ring electrode comprises multiple disconnected electrodes. 
     In one embodiment, the transmitter transmits electric signals via the ring electrode and the tip section during a zeroth time period. In another embodiment, the transmitter transmits electric signals via the tip section during a first time period. Alternatively, the first time period is after the zeroth time period. 
     In one embodiment, electric signals emitted from the ring electrode and the tip section contains the same frequency group. Alternatively, electric signal emitted from the ring electrode contains frequency group different to the frequency group contained in the electric signal emitted from the tip electrode. 
     One aspect of the present application is to provide a method for detecting a position of a transmitter, wherein the transmitter comprises a tip section and a ring electrode surrounding the tip section, wherein the tip section is not electric coupling to the ring electrode, the method comprises detecting electric signals emitted from the ring electrode and the tip section during a zeroth time period; and detecting electric signals emitted from the tip section during a first time period. 
     One aspect of the present application is to provide a touch sensitive processing apparatus for detecting a position of a transmitter, wherein the transmitter comprises a tip section and a ring electrode surrounding the tip section, wherein the tip section is not electric coupling to the ring electrode, the touch sensitive processing apparatus is coupled to a touch panel which comprises a plurality of first electrodes and a plurality of second electrodes and multiple sensing points located where the intersections, the touch sensitive processing apparatus is configured for detecting electric signals emitted from the ring electrode and the tip section during a zeroth time period; and detecting electric signals emitted from the tip section during a first time period. 
     One aspect of the present application is to provide a touch sensitive system, comprises a transmitter, a touch panel, and a touch sensitive processing apparatus coupled to the touch panel. The transmitter comprises a tip section and a ring electrode surrounding the tip section, wherein the tip section is not electric coupling to the ring electrode. The touch sensitive processing apparatus is coupled to a touch panel which comprises a plurality of first electrodes and a plurality of second electrodes and multiple sensing points located where the intersections, the touch sensitive processing apparatus is configured for detecting electric signals emitted from the ring electrode and the tip section during a zeroth time period; and detecting electric signals emitted from the tip section during a first time period. 
     In one embodiment, electric signal emitted from the ring electrode and the tip section contains the same frequency group. Alternatively, electric signal emitted from the ring electrode contains frequency group different to the frequency group contained in the electric signal emitted from the tip electrode. 
     In one embodiment, the method further comprises calculating a first centroid position of the transmitter according to the electric signal detected during the zeroth time period. Alternatively, the method further comprises calculating a second centroid position of the transmitter according to the electric signal detected during the first time period. 
     In one embodiment, the method further comprises calculating a surface position where the transmitter touches the touch panel according to the first centroid position and the second centroid position, wherein the surface position is the position where the axis of the tip section projecting to a surface layer of the touch panel. 
     In one embodiment, the method further comprises calculating a display position where the transmitter touches the touch panel according to the first centroid position and the second centroid position, wherein the display position is the position where the axis of the tip section projecting to a display layer of the touch panel. 
     In one embodiment, the method further comprises calculating an inclination angle of the transmitter touches the touch panel according to the first centroid position and the second centroid position. 
     One aspect of the present application is to provide a method for calculating a surface position where a transmitter touches a touch panel, the method comprises: receiving a first centroid position of the transmitter, wherein the first centroid is calculated according to electric signals emitted from a ring electrode and a tip section of the transmitter, receiving a second centroid position of the transmitter, wherein the first centroid is calculated according to electric signals emitted from the a tip section of the transmitter; and calculating the surface position where the transmitter touches the touch panel according to the first centroid position and the second centroid position, wherein the surface position is the position where the axis of the tip section projecting to a surface layer of the touch panel. 
     One aspect of the present application is to provide a method for calculating a display position where a transmitter touches a touch panel, the method comprises: receiving a first centroid position of the transmitter, wherein the first centroid position is calculated according to electric signals emitted from a ring electrode and a tip section of the transmitter, receiving a second centroid position of the transmitter, wherein the second centroid position is calculated according to electric signals emitted from the a tip section of the transmitter; and calculating the display position where the transmitter touches the touch panel according to the first centroid position and the second centroid position, wherein the display position is the position where the axis of the tip section projecting to a display layer of the touch panel. 
     One aspect of the present application is to provide a method for calculating an inclination angle of a transmitter touches a touch panel, the method comprises: receiving a first centroid position of the transmitter, wherein the first centroid position is calculated according to electric signals emitted from a ring electrode and a tip section of the transmitter, receiving a second centroid position of the transmitter, wherein the second centroid position is calculated according to electric signals emitted from the a tip section of the transmitter; and calculating the inclination angle according to the first centroid position and the second centroid position. 
     In one embodiment, the first centroid position is calculated during a zeroth time period. In one embodiment, the second centroid position is calculated during a first time period. Alternatively, the first time period is after the zeroth time period. In one embodiment, electric signal emitted from the ring electrode contains frequency group different to the frequency group contained in the electric signal emitted from the tip electrode. 
     One aspect of the present application is to provide a display method, comprises: receiving a position of a transmitter; receiving an inclination angle of the transmitter; determining a display area according to the position and the inclination angle. 
     In one embodiment, the position is one of the followings: a first centroid position, a second centroid position, a surface position; and a display position. The first centroid position is calculated according to electric signals emitted from a ring electrode and a tip section of the transmitter. The second centroid position is calculated according to electric signals emitted from the tip section of the transmitter. The surface position is the position where the axis of the tip section projecting to a surface layer of the touch panel. The display position is the position where the axis of the tip section projecting to a display layer of the touch panel. In one embodiment, electric signal emitted from the ring electrode contains frequency group different to the frequency group contained in the electric signal emitted from the tip electrode. 
     In one embodiment, the display area comprises an ellipse. Alternatively, the position is located one of the followings: a center of the ellipse, one of two focal points of the ellipse; and one of intersections of the semi-major axis and the ellipse. In one embodiment, the semi-major axis is corresponding to the direction of the inclination angle. 
     In one embodiment, the display area comprises a tear drop shape. Alternatively, the position is located one of the followings: a center of the tear drop shape, a top of the tear drop shape; and an end of the tear drop shape. In one embodiment, the direction of the tear drop shape is corresponding to the direction of the inclination angle. 
     In one embodiment, the direction of the display area is corresponding to the direction of the inclination angle. Alternatively, the size of the display area is corresponding to the inclination angle. Alternatively, the color of the display area is corresponding to one of the followings: the inclination angle; and the direction of the inclination angle. 
     In one embodiment, it further comprises receiving a pressure of the transmitter; the size of the display area is corresponding to the pressure. 
     One aspect of the present application is to provide a method for controlling the transmitter, comprises: transmitting a first electric signal with a first signal strength if a force sensor of the transmitter does not sense any force; transmitting a second electric signal with a second signal strength if the force sensor does sense force, wherein the first signal strength is larger than the second signal strength. 
     In one embodiment, the force sensor comprises a tip section of the transmitter. 
     In one embodiment, the transmitter further comprises a ring electrode. The first electric signal is transmitted via the tip section and the ring electrode, the second electric signal is transmitted via the tip section. 
     One aspect of the application is to provide a transmitter, comprises a force sensor and a control unit, which is configured to transmitting a first electric signal with a first signal strength if a force sensor of the transmitter does not sense any force; transmitting a second electric signal with a second signal strength if the force sensor does sense force, wherein the first signal strength is larger than the second signal strength. 
     Code Division Multiple Access (CDMA) is a wireless spread spectrum telecommunication technology adopted in the third generation of mobile telecommunication service. In wireless telecommunication techniques, spread spectrum means the bandwidth consumed by the carrier signal itself exceeds the bandwidth of the contents carried by the carrier signal. Using a carrier signal with bigger bandwidth allows for better tolerance to interfering noise signals during transmission. Direct Sequence Spread Spectrum (DSSS) is one of spread spectrum techniques. DSSS modulation technique employs a bit sequence code called a pseudo noise (PN). The bit sequence code or PN code includes pulse waves each with a short period, which period may be called a chip. The period of a chip is shorter than that of a data or signal code (thereinafter data code). In other words, the bandwidth consumed by a PN code is larger than that consumed by a data code. Therefore, modulating a data code of a smaller bandwidth into a PN code of a larger bandwidth means the bandwidth of the carrier signal after modulation matches or is similar to that of the PN code. 
     During the process of modulation with a carrier signal, a main step is to multiply a data code and a PN code, which PN code is usually a pseudo random sequence usually including a combination of 1 and −1. One characteristic of PN code is that multiplying a sequence of PN code by the same PN code returns the same PN code, because 1×1=1 and −1×−1=1. This multiplication with the same PN code is called despreading. Accordingly, when the receiving end also knows the sequence of PN code used in the modulation process, it can perform a process of despreading to obtain the data or content code carried by the carrier signal. 
     Referring to  FIG. 30 , some waveforms of a spread spectrum technique are illustrated. The waveform on the top portion of  FIG. 30  is a data code, the waveform on the middle portion of  FIG. 30  is a pseudo random sequence or a so-called PN code, and the waveform on the bottom portion of  FIG. 30  is a carrier signal. According to  FIG. 30  it can be known that when the electric potential of the data code is high, the waveforms of the carrier signal and the PN code are opposite to each other. When the electric potential of the data code is low, the waveforms of the carrier signal and the PN code are the same. In other words, the receiving end can compare the waveforms of the carrier signal and the PN code, and when the two waveforms are opposite to each other, the receiving end can infer that the electric potential of the data code is high at this time. Conversely, when the waveforms of the carrier signal and the PN code are the same, the receiving end can infer that the electric potential of the data code is low at this time. Accordingly, the receiving end can infer the state of the electric potential of the data code as long as the PN code used is known. 
     Referring to  FIG. 31 , which shows a variant of the embodiment as shown in  FIG. 1 . The touch sensitive system  100  further includes a first stylus  111  and/or a second stylus  112 . In one embodiment, these styli  111  and  112  are active. 
     In some embodiments, the active stylus  111  or  112  may be commanded to code the sensing values from each sensor thereon to the data codes mentioned above. The so-called sensing value of a sensor may include but not limited to the following: a pressure value on a tip section of stylus; sensing value presenting whether a button being pressed or not; sensing value of attitude of a gyroscope; sensing value of acceleration of an accelerometer; sensing value of battery power; serial number of stylus; and wireless signal intensity received by stylus. Then, the active stylus  111  or  112  codes the data code(s) mentioned above to carrier signal(s) by the process of spread spectrum according to certain a PN code. After that, the active stylus  111  or  112  emits the electrical signals including the carrier signals by the tip section thereof. After receiving the electrical signals, the touch sensitive processing apparatus of the touch sensitive screen at least obtains the following message: the proximate position of the active stylus  111  or  112  on the touch sensitive screen; the PN code form used by the active stylus  111  or  112 , as well as the content of the aforementioned data code. 
     In the above-described process, the touch sensitive processing apparatus  130  at the receiving end must synchronize or align the received carrier signal and PN code, in order to obtain the correct (state of the) data code. However, when the active stylus  111  or  112  emits electrical signal, the touch sensitive processing apparatus  130  can not necessarily immediately synchronize the received carrier signal and PN code, which results in difficulties in obtaining/inferring the data code. 
     The receiving end can usually postpone the multiplication of a received known carrier signal or a local oscillator (L0) signal produced by the receiving end, and a known PN code, for a period of time, and then perform the multiplication, which postponing of multiplication may be called a correlation. When two signals are not synchronous, the calculated value of their correlation will not exceed a threshold value. Conversely, when the two signals are synchronous, the calculated value of their correlation will exceed the threshold value. And when the two signals are not synchronous, the receiving end can repetitively adjust the postponing period until the two signals are synchronous or aligned. 
     In one embodiment of the present invention, electrical signal or the carrier signal emitted by the active stylus may comprise a signal frame including a preamble code followed by a data code section. The data code section may be used for transmitting a sensing state of a sensor on the stylus. For example, sensing values e.g. resulting from sensing whether a button on the stylus has been pressed down, or associated with the pressure value sensed by the tip section of the stylus, can be transmitted. 
     In a variant of this embodiment, the active stylus  111  or  112  can emit a complete signal frame described above at intervals, to inform of the state of the sensor thereof. In another variant of this embodiment, different active styluses may have different preamble codes and/or PN codes, enabling the touch sensitive processing apparatus  130  to identify and/or distinguish at least two active styluses simultaneously approaching or touching the touch sensitive screen  120 . For example, the first active stylus  111  emits a first preamble code modulated by a first PN code, the second active stylus  112  emits a second preamble code modulated by a second PN code. And then, the touch sensitive processing apparatus  130  demodulates or performs despreading to the received signal by the first PN code and the second PN code respectively, it can determine the first preamble code and/or the second preamble code having been received. 
     When the touch sensitive processing apparatus  130  knows the electrical signal having two preamble codes, it can determine the first active stylus  111  and the second active stylus  112  approximate the touch sensitive screen  120  according to the first PN code and the second PN code which are correspondingly associated to the first active stylus  111  and the second active stylus  112 . Since the touch sensitive processing apparatus  130  knows the timing of the first PN code and the second PN code, it can make the first and the second PN codes respectively synchronize the signal frames emitted by the first active stylus  111  and the second active stylus  112 , and then decodes the data code section behind the signal frame. 
     In one embodiment of the present invention, in order to reach the synchronous state soon, some or all of the second electrodes  122  are connected to the same line or channel, called synchronization line or synchronization channel, and the touch sensitive processing apparatus is responsible for detecting on the synchronization line or synchronization channel and performing synchronization with respect to the known preamble code. 
     Persons having ordinary skill in the art can appreciate that when the touch sensitive processing apparatus  130  has known the PN code and the intendedly transmitted preamble code, the touch sensitive processing apparatus  130  can synchronize with the carrier signal by using well known technique(s), or find the phase shift between the carrier signal and the local oscillator signal. When ascertaining the phase shift between the two signals, any of the first electrodes  121  receiving the electrical signal is caused to decode the following data code section, in order to obtain the sensor state transmitted by the active stylus  111  or  112 . 
     In one embodiment of the present invention, the aforementioned decoding step may be performed to decode the following data code section with respect to the carrier signal received by one of the first electrodes  121 , wherein the received carrier signal used for decoding has the largest signal amount among all carrier signals received by all the first electrodes  121  and/or second electrodes  122 . 
     In another embodiment of the present invention, the aforementioned decoding step may be performed to decode the following data code section with respect to the carrier signals received by some of the first electrodes  121 , to obtain data codes which should match or be similar to each other. If the data codes obtained do not match, the data codes obtained for the most instances may be regarded as the right one. 
     In addition, among the carrier signals received by the multiple first electrodes  121 , after adjustment using the phase shift, the carrier signal that is the most correlated with the local oscillator signal should have the smallest noise and is usually received by one of the first electrodes  121  that is closest to the active stylus  111  or  112 . Accordingly, the position of the active stylus  111  or  112  relative to each of the first electrodes  121  may be calculated based on deviations of multiple instances of correlation involving the carrier signal received by each first electrode  121  and adjusted by using the phase shift mentioned above. In other words, the coordinate(s) of the position of the active stylus  111  on the second axis can be calculated as well. 
     Referring to  FIG. 32 , a flowchart of despreading method  3200  according to an embodiment of the present invention is illustrated. The touch sensitive processing apparatus  130  shown in  FIG. 31  could perform the steps of the flowchart shown in  FIG. 32 , whatever by software, hardware, or the combination of software and hardware. It should be noted that the step numbers in  FIG. 32  do not affect the steps performed in order except that there is a causal relationship between the steps. Moreover, other steps which do not relate to the present invention may be inserted between the steps as well. 
     At step  3210 , coupling at least two of the second electrodes as a synchronization channel. The touch sensitive processing apparatus  130  may use analog switch or digital adder to implement this step. In a variant, the synchronization channel couples all of the second electrodes. 
     At step  3220 , despreading a first preamble code of a first signal frame of received signal from the synchronization channel to retrieve a first synchronization information according to a first pseudo noise code. 
     At step  3230 , decoding first data codes behind the first preamble code of received signal from at least one of the first electrodes in accordance with the first synchronization information and the first pseudo noise code. 
     In a variation, an electrical signal used for decoding the first data codes is from one of the multiple first electrodes which receive a largest electrical signal amount or a strongest electrical signal. In another variation, an electrical signal used for decoding the first data codes is from some of the multiple first electrodes. In still another variation, the despreading method further includes: calculating multiple deviations of signal correlations of the multiple first electrodes according to the first synchronization information; and calculating a position of the first active stylus on the second axis according to the multiple deviations. 
     At step  3240 , despreading a second preamble code of a second signal frame of received signal from the synchronization channel to retrieve a second synchronization information according to a second pseudo noise code. 
     At step  3250 , decoding second data codes behind the second preamble code of received signal from at least one of the first electrodes in accordance with the second synchronization information and the second pseudo noise code. 
     In a variation, an electrical signal used for decoding the second data codes is from one of the multiple first electrodes which receives a largest electrical signal amount or a strongest electrical signal. In another variation, an electrical signal used for decoding the second data codes is from some of the multiple first electrodes. In still another variation, the despreading method further includes: calculating multiple deviations of signal correlations of the multiple first electrodes according to the second synchronization information; and calculating a position of the second active stylus on the second axis according to the multiple deviations. 
     One of the advantages of this invention is that the touch sensitive processing apparatus  130  can rapidly synchronize the electrical signals modulated by DSSS in one signal frame and then decode the data code section emitted by the active stylus/styli  111  and/or  112 . Another advantage of this invention is that when several active styli, such as  111  and  112 , operate at the same time, all of them are allowed to emit electrical signals simultaneously. For example, as long as they use different pseudo noise codes, even if they emit electrical signals simultaneously, the touch sensitive processing apparatus  130  is still able to distinguish the signal frames and data codes emitted from them in the received signals. 
     In an embodiment, this invention provides a despreading method being applicable to a touch sensitive screen which includes multiple first electrodes being parallel to a first axis and multiple second electrodes being parallel to a second axis. The despreading method includes the following steps: coupling at least two of the second electrodes as a synchronization channel; despreading a first preamble code of a first signal frame of received signal from the synchronization channel to retrieve a first synchronization information according to a first pseudo noise code; and decoding a first data codes behind the first preamble code of received signal from at least one of the first electrodes in accordance with the first synchronization information and the first pseudo noise code. 
     In certain embodiments, the first signal frame is from a first active stylus approaching the touch sensitive screen, the first data codes include at least one type of following information: a pressure on a tip section of stylus; sensing value presenting whether a button being pressed or not; sensing value of attitude of a gyroscope; sensing value of acceleration of an accelerometer; sensing value of battery power; serial number of stylus; and wireless signal intensity received by stylus. 
     In certain embodiments, the synchronization channel couples all of the multiple second electrodes. 
     In certain embodiments, an electrical signal used for decoding the first data codes is from one of the multiple first electrodes which receives a largest electrical signal amount or a strongest electrical signal. 
     In certain embodiments, an electrical signal used for decoding the first data codes is from some of the multiple first electrodes. The despreading method further includes the following steps: calculating multiple deviations of signal correlations of the multiple first electrodes according to the first synchronization information; and calculating a position of the first active stylus (emitting the first signal frame) on the second axis according to the multiple deviations. 
     In certain embodiments, the despreading method further includes the following steps: despreading a second preamble code of a second signal frame of received signal from the synchronization channel to retrieve a second synchronization information according to a second pseudo noise code; and decoding a second data codes behind the second preamble code of received signal from at least one of the multiple first electrodes in accordance with the second synchronization information and the second pseudo noise code, wherein the second signal frame is from a second active stylus approaching the touch sensitive screen. 
     In certain embodiments, the first signal frame and the second signal frame have at least some parts concurrently appearing in the signal received by the multiple first electrodes. 
     In an embodiment, this invention provides a touch sensitive system for despreading. The touch sensitive system includes a touch sensitive screen including multiple first electrodes being parallel to a first axis and multiple second electrodes being parallel to a second axis, and a touch sensitive processing apparatus connected to the multiple first electrodes and the multiple second electrodes. The touch sensitive processing apparatus is configured to perform the following steps including: coupling at least two of the multiple second electrodes as a synchronization channel; despreading a first preamble code of a first signal frame of received signal from the synchronization channel to retrieve a first synchronization information according to a first pseudo noise code; and decoding a first data codes behind the first preamble code of received signal from at least one of the multiple first electrodes in accordance with the first synchronization information and the first pseudo noise code. 
     In an embodiment, this invention provides a touch sensitive processing apparatus for despreading. The touch sensitive processing apparatus is connected to multiple first electrodes on a touch sensitive screen which are parallel to a first axis and multiple second electrodes on the touch sensitive screen which are parallel to a second axis. The touch sensitive processing apparatus is configured to perform the following steps including: coupling at least two of the multiple second electrodes as a synchronization channel; despreading a first preamble code of a first signal frame of received signal from the synchronization channel to retrieve a first synchronization information according to a first pseudo noise code; and decoding a first data codes behind the first preamble code of received signal from at least one of the multiple first electrodes in accordance with the first synchronization information and the first pseudo noise code. 
     In certain embodiments, the first signal frame is from a first active stylus approaching the touch sensitive screen, the first data codes include at least one type of following information: a pressure on a tip section of stylus; sensing value presenting whether a button being pressed or not; sensing value of attitude of a gyroscope; sensing value of acceleration of an accelerometer; sensing value of battery power; serial number of stylus; and wireless signal intensity received by stylus. 
     In certain embodiments, the synchronization channel couples all of the multiple second electrodes. 
     In certain embodiments, an electrical signal used for decoding the first data codes is from one of the multiple first electrodes which receives a largest electrical signal amount. 
     In certain embodiments, an electrical signal used for decoding the first data codes is from some of the multiple first electrodes. The touch sensitive processing apparatus is configured to further perform the following steps including: calculating multiple deviations of signal correlations of the multiple first electrodes according to the first synchronization information; and calculating a position of the first active stylus (emitting the first signal frame) on the second axis according to the multiple deviations. 
     In certain embodiments, the touch sensitive processing apparatus is configured to further perform the following steps including: despreading a second preamble code of a second signal frame of received signal from the synchronization channel to retrieve a second synchronization information according to a second pseudo noise code; and decoding a second data codes behind the second preamble code of received signal from at least one of the multiple first electrodes in accordance with the second synchronization information and the second pseudo noise code, wherein the second signal frame is from a second active stylus approaching the touch sensitive screen. 
     In certain embodiments, the first signal frame and the second signal frame have at least some parts concurrently appearing in the signal received by the multiple first electrodes. 
     Please refer to  FIG. 33 , which depicts a diagram of an embodiment of an active stylus  111  in accordance with the present invention. The active stylus  111  may comprise a controller  3310 , a clock signal module  3320 , a battery  3330 , the first component  221  with a first impedance Z1, the second component  222  with a second impedance Z2, and a tip section  230 . The controller  3310  is configured for simultaneously generating two different pseudo random number coded signals  3311  and  3312  to the first component  221  and the second component  222 , respectively. The controller  3310  may comprise analog and digital circuits, signal processor, generic computing processor, volatile or non-volatile memory for storing instructions and data for the processor(s). The signal processor and/or processor may run on one or more instruction sets such as ARM instruction set, Intel 8051 instruction set, and etc. 
     The battery  3330  may be rechargeable or non-rechargeable. The controller  3310  may include charging circuits for the rechargeable battery  3330 . Electrical power stored in the battery  3330  is supplied to the controller  3310  and the clock signal source  3320  for operations. The clock signal module  3320  may be any kind of oscillator(s) which outputs one or more clock signals to the controller  3310 . For example, the oscillator may be crystal oscillator, XO, TCXO, OCXO, or VCXO. The controller  3310  may comprises frequency divider or frequency multiplier to generate clock signals for data and for carrier. As shown in  FIG. 30 , frequency of data codes is slower than the carrier signal. The clock signal module  3320  are configured to provide one or more clock signals for the encoding process described. 
     Multiple pseudo random number (PN) codes are stored in the controller  3310 . A first PN code is corresponding to the signal  3311  and a second PN code is corresponding to the signal  3312 . All of these applicable PN codes are orthogonal to each other. It means that any two of the PN codes are orthogonal. 
     In one embodiment, mapping relationship between the signal  3311  and the PN code may be configurable and stored in the controller  3310 . For example, there may be 10 PN codes stored in five active styli  111 . Each of the styli  111  is configured to use a set of two PN codes. Hence, five sets of PN codes emitted from the styli  111  simultaneously can be distinguished by the touch sensitive processing apparatus  130 . The position of each of the styli  111  can be found according to the electrical signal emitted from the tip section  230 . 
     For providing configuration interface of the mapping relationship, the stylus  111  may include physical human-machine interface for input and/or output. In one example, the stylus  111  may include visual and/or audio indicator for showing the set of PN codes that the controller  3310  use. The visual or audio indicator is connected and controlled by the controller  3310 . 
     The visual indicator may include multiple light bulbs, LED, or equivalents, where each of the light is corresponding to each set of the PN codes. Alternatively, the visual indicator may include one LED which flashes one or multiple times in a short period to show the configured mapped set of the PN codes. Or the visual indicator may present different colors to show which set of the PN codes is configured. 
     Similarly, the audio indicator may include a beeper which may be used to prompt user by number of beeps in a short period. Or a speaker may be used to output voices and/or sounds to advertise the configured mapped set of the PN codes. 
     An input button, a switch or a knob of the stylus  111  may be used to configure the set of PN codes. The state of the button, the switch or the knob may be used to indicate which set of the PN codes is configured. 
     Apart from the physical human-machine interface, the stylus  111  may comprise a communication unit for receiving the configuration setting from remote machine to the controller  3310 . The communication unit may be compatible to wired or wireless industrial standards such as Bluetooth, USB, Wireless USB, UWB, and etc. Persons having ordinary skill in the art are able to understand similar communication units are widely used in modern consumer electronics such as smartphone, mobile computer, and etc. For example, the transmitter wireless communication unit  770  as shown in  FIGS. 7A-7D  may be used here. 
     A remote machine may be used to connect to the communication unit for reading and/or configuring the set of the PN codes. A configuration program may be run on the remote machine to read or to set the PN codes of the connected stylus  111 . In one embodiment, the remote machine may connect to multiple styli  111  simultaneously for ensuring that each one of the connected styli  111  use different set of PN codes. Once the remote machine detects that sets of the PN codes used by connected styli  111  are conflicted, the remote machine may automatically assign different sets of the PN codes to the conflicted styli  111 . 
     In some embodiments, the set of PN codes used by the stylus  111  is fixed or hard-coded before shipping out of factory. The stylus  111  may be painted in a particular color or a visual identification may be shown on the stylus  111 . Users may check colors or visual identifications of their styli  111 . If they hold different colored styli  111 , the touch sensitive processing apparatus  130  is able to identify each of the styli  111 . 
     The stylus  111  may comprise one or more human interfaces or sensors such as buttons, knobs, attitude sensors, gyroscopes, accelerometers, electrical signal receiver, and etc. The status of these human interfaces and sensors can be collected periodically by the controller  3310 . The status or any other information such as a unique identification code of the stylus  111  to be sent to the touch sensitive processing apparatus  130  may be treated as data codes shown in  FIG. 30 . The data codes to be sent and the first PN code may be modulated by the controller  3310 . A person having ordinary skill in the art can understand that CDMA or direct sequence spread spectrum technique is widely used in the 3G telecommunication. The controller  3310  comprises hardwired circuits and/or embedded processor for modulation. Traditionally, a multiplier is used to generate the carrier signal according to the data code and the PN code. If there is no need to send any data code, the signals  3311  and  3312  received by the tip section  230  may be the first PN code and the second PN code, respectively. 
     The data codes may be modulated according to the first PN code to generate the signal  3311 . The data codes may be also modulated according to the second PN code to generate the signal  3312 . In other words, the data codes may be transmitted via one or both of the signals  3311  and  3312 . The touch sensitive processing apparatus  130  may despread or decode the data codes emitted from the tip section  230  according to one or both the first and the second PN codes. If the data codes decoded according to the first PN code is consistent with the data codes decoded according to the second PN code, the data codes are trustworthy. Otherwise, the two different data codes may be discarded or disregarded. 
     The active stylus  111  may further comprise a receiver for synchronization with the touch sensitive processing apparatus  130 . As described in the previous paragraphs, a beacon signal may be emitted via electrodes of the touch panel  120  by the touch sensitive processing apparatus  130  for synchronization. The tip section  230  may be served as a receiving antenna for receiving the beacon signal. Beacon signals as shown in  FIGS. 9A-9F  may be adopted to this embodiment. 
     The controller  3310  may connect to the tip section  230  for receiving the beacon signal. In order to correctly receive and identify the beacon signal, the controller  3310  may include circuits such as integrator, sampler, amplifier, analog to digital converter, adder, and any other circuits for receiving the beacon signal. The received signal may be further processed by the processor to retrieve the synchronization signal and/or message carried by the beacon signal from interference. Once the beacon signal is received, the controller  3310  may transmit the signals  3311  and  3312  to the tip section  230  after a predetermined turnaround period which is known to the touch sensitive processing apparatus  130 . Or the beacon signal may include a time period parameter to indicate length of the turnaround period. 
     If there are multiple styli  111  operating in the touch sensitive system  100 , the beacon signal with no turnaround time period would cause all of the styli  111  transmitting electrical signals in the same time. However, since the electrical signals transmitted by these styli  111  are encoded by different PN codes, the touch sensitive processing apparatus  130  can distinguish each of the styli  111 . 
     In one embodiment, the beacon signal may further include an identification corresponding to one of the styli  111  and a turnaround time period. If one of the styli  111  receives the beacon signal including its identification, the stylus  111  would transmit the electrical signal via the tip section  230  at the designated turnaround time period indicated in the beacon signal. In order to prevent or alleviate interference in the touch sensitive system  100 , the touch sensitive processing apparatus  130  may emit a beacon signal with multiple combinations of stylus identifications and designated turnaround time periods or time slots. 
     Alternatively, the touch sensitive processing apparatus  130  may transmit multiple beacon signals for the styli  111 . The beacon signals are modulated differently. For example, the modulation of these beacon signals may be varied in frequency, phase, amplitude and etc. Therefore each of the styli  111  can listen to its designated beacon signal. 
     In one embodiment, the touch sensitive system  100  may utilize multiple modulations of beacon signal for multiple groups of styli  111 . In each modulation of beacon signal, multiple combinations of stylus identifications and designated turnaround timer periods or time slots may be included. The touch sensitive processing apparatus  130  may control refresh rates of each modulation of beacon signal. If one of the styli  111  goes idle, the beacon signal sent to the idle stylus  111  may be delayed or omitted. If one of the styli  111  goes wildly, the touch sensitive processing apparatus  130  may send more beacon signal to the stylus  111  than the rest of the styli  111  in order to get the positions and/or the data codes more frequently and precisely. Persons having ordinary skill in the art can understand that the touch sensitive processing apparatus  130  may adjust the refresh/update rate of each stylus  111  by controlling the transmission of the corresponding beacon signal. 
     Alternatively, the beacon signal may be emitted by the host  140 . For example, the touch sensitive processing apparatus  130  may use a wireless communication unit equipped by the host  140  to transmit the beacon signal. Based on nature of the wireless communication protocols, the beacon signal may be broadcasted or unicasted to each of the styli  111 . For example, Bluetooth protocol defines a broadcast mechanism to send advertising message. The beacon signal may be carried out by the broadcast mechanism of Bluetooth protocol. Any stylus  111  receiving the advertising message serving as the beacon signal is synchronized accordingly. Otherwise, the beacon signal may be unicasted wirelessly from the host  140  to the stylus  111 . Persons having ordinary skill in the art can understand the synchronization between the stylus  111  and the touch sensitive processing apparatus  130  is done by the beacon signal which may be transmitted via the touch panel  120  or via wired or wireless communication channel in between. 
     Although the synchronization may be achieved by the beacon signal, the touch sensitive processing apparatus  130  may synchronize the electrical signal by itself. The controller  3310  may transmit signal with a preamble code via one or both of the first component  221  and the second component  222 . The preamble code may be encoded by one or both the first PN code and the second PN code. Eventually the electrical signal emitted via the tip section  230  includes the preamble code and/or data codes. Once the touch sensitive processing apparatus  130  receives electrical signal via the touch panel  120 , the received electrical signal would be amplified, sampled, converted into digital forms and stored in the memory. Hence, circuits or processor embedded in the touch sensitive processing apparatus  130  may compare the stored signal with the preamble code corresponding to the stylus  111 . In case the stored signal is fully or partial matched with the preamble code, the touch sensitive processing apparatus  130  is able to calculate the receiving timing of the stored preamble code. Consequently, timing of a next transmission from the stylus  111  can be calculated by the touch sensitive processing apparatus  130  according to the stored preamble code. In some examples, the match of the preamble code is fast enough that the data codes in the same transmission can be decoded; especially in case the preamble code is sufficiently enduring. A sliding window mechanism on the memory storing the received signal may be applied to find the preamble code. 
     When the preamble code is found, the touch sensitive processing apparatus  130  can calculate a position that the stylus  111  touching or approaching the touch panel  120  according to the received signals. If two or more styli  111  use different sets of the PN codes, the preamble codes of these styli  111  are different and orthogonal. Even the preamble codes are received simultaneously, the touch sensitive processing apparatus  130  are able to find out the positions of the styli  111  touching or approaching the touch panel  120 . 
     Referring to  FIG. 34 , it shows a block diagram of a touch sensitive processing apparatus  130  according to an embodiment of the present invention. The touch sensitive processing apparatus  130  may include an embedded processor  3440 , which is used for connecting and controlling an interconnection network  3410 , a driving circuit  3420 , a sensing circuit  3430 , and a host interface  3450 . The driving circuit  3420  may respectively connect each first electrode  121  and each second electrode  122  via the interconnection network  3410  to use these electrodes to emit a driving signal. The sensing circuit  3430  may respectively connect each first electrode  121  and each second electrode  122  via the interconnection network  3410  to use these electrodes to sense signal(s). The embedded processor  3440  can communicate with the host  140  through the host interface  3450 . The embedded processor  3440  may perform a program module stored in non-volatile memory to detect the abovementioned approximate object(s) and event(s). 
     The interconnection network  3410  is dynamically configurable by the embedded processor  3440 . The driving circuit  3420  may be connected to one or more of the first electrodes  121  and/or the second electrodes  122  via the interconnection network  3410 . Similarly, the sensing circuit  3430  may be connected to one or more of the first electrodes  121  and/or the second electrodes  122  via the interconnection network  3410 . In one embodiment, the driving circuit  3420  and the sensing circuit  3430  are collectively called “analog frontend” circuits which may comprises any combination of amplifiers, filters, samplers, integrator, digital-to-analog converter, analog-to-digital converter, adder, multiplier, variable resistors, and etc. Apart from the analog circuits including the driving circuit  3420  and the sensing circuit  3430 , the embedded processor  3440  may deal with digital parts of signal processing. The host interface  3450  is used to connect the embedded processor  3440  and the host  140 . Typically, the host interface  3450  may be compatible to industrial standards such as USB, I2C, PCI, PCI-Express, SCSI, and etc. Persons with ordinary skill in the art can understand the host interface  3450  is very common in modern electronics. 
     Please refer to  FIG. 35 , which illustrates a flowchart diagram practiced by the controller  3310  as shown in  FIG. 33  in accordance to an embodiment of the present invention. The flow may be also applicable to the stylus  111  as shown in  FIG. 33 . Unless a causal relationship is noted, the present invention does not limit execution sequences of any two of the steps as shown in  FIG. 35 . 
     Optional step  3510 : receiving configuration setting of a first PN code and a second PN code. The configuration mechanism is already described. 
     Optional step  3520 : receiving a beacon signal. The touch sensitive processing apparatus  130  may transmit the beacon signal via at least one of the first electrodes  121  or the second electrodes  122  of the touch panel  120  to the stylus  111 . Alternatively, the touch sensitive processing apparatus  130  may ask a communication unit of the host  140  to transmit the beacon signal to a corresponding communication unit of the stylus  111 . 
     Optional Step  3530 : decoding identification and turnaround time period parameter. If the optional step  3520  is performed and a beacon signal is received, the beacon signal may comprise identification and/or turnaround time period parameter for a specified stylus  111  or a specified group of styli  111 . Thus, the identification of stylus  111  and/or the turnaround time period specified in the beacon signal is decoded. 
     Optional Step  3540 : generating data codes according to status of onboard sensors. If the stylus  111  comprises one or more onboard sensors such as button, switch, knob, battery volume and etc. in additional to the pressure sensor connected to the first component  221 , data codes may be generated to reflect the status of onboard sensors and/or other information such as the identification of the stylus  111 , and/or model and vendor name of the stylus  111 . 
     Step  3550 : transmitting a first preamble code and/or data codes according to the first PN code to a first component having variable impedance reflecting a pressure. The transmitted signal may be the first preamble code, the data codes, or both of them. Since they are all encoded by the first PN code, the touch sensitive processing apparatus  130  is able to detect and decode the transmitted signals via the tip section  230  and the electrodes  121  and/or  122  in theory. 
     Step  3560 : transmitting a second preamble code and/or data codes according to the second PN code to a second component having fixed impedance. The steps  3550  and  3560  may be performed simultaneously. The transmitted signal may be the second preamble code, the data codes, or both of them. Since they are all encoded by the second PN code, the touch sensitive processing apparatus  130  is able to detect and decode the transmitted signals via the tip section  230  and the electrodes  121  and/or  122  in theory. 
     Please refer to  FIG. 36A , which illustrates a flowchart diagram practiced by the embedded processor  3440  in accordance to an embodiment of the present invention. The flow is applicable to the touch sensitive processing apparatus  130  as shown in  FIGS. 33 and 34 . Unless a causal relationship is noted, the present invention does not limit execution sequences of any two of the steps as shown in  FIG. 36A . If a beacon signal is used as a synchronization signal in the system  100 , the flow begins with the step  3610 . 
     Optional step  3610 : transmitting a beacon signal. This step is corresponding to the step  3520  as shown in  FIG. 35 . The touch sensitive processing apparatus  130  may transmit the beacon signal via at least one of the first electrodes  121  or the second electrodes  122  of the touch panel  120  to the stylus  111 . Alternatively, the touch sensitive processing apparatus  130  may ask a communication unit of the host  140  to transmit the beacon signal to a corresponding communication unit of the stylus  111 . Optionally, the beacon signal may comprise one or more identifications and/or turnaround time period parameters for one ore more specified styli  111  or a specified group of styli  111 . 
     Optional step  3620 : waiting for a turnaround time period. If the transmitted beacon signal indicates the turnaround time period, the embedded processor  3440  or the touch sensitive processing apparatus  130  may wait or sleep in this period. Alternatively, the embedded processor  3440  may perform other functions such as capacitive sensing for external conductive objects touching or approaching the touch panel  120  in this turnaround time period. 
     Step  3630 : receiving electrical signals via electrodes of a touch panel. The stylus  111  transmits electrical signals via the tip section  230  to at least one of the electrodes  121  and  122  of the touch panel  120 . The electrical signals are received by the sensing circuit  3430  of the touch sensitive processing apparatus  130  via the electrodes near the tip section  230 . 
     Optional step  3640 : despreading a first preamble code of received electrical signals in accordance with a first PN code. If the electrical signals transmitted by the stylus  111  comprise the first preamble code, the embedded processor  3440  of the touch sensitive processing apparatus  130  is able to despread the first preamble code in accordance with the first PN code. In some embodiments, the system  100  does not utilize the beacon signal to synchronize the timing of transmitting electrical signals, i.e., the steps  3610  and  3620  are omitted, the embedded processor  3440  may be required to use sliding window technique to acquire the first preamble code in the received electrical signals because the embedded processor  3440  has no idea when the electrical signals would be transmitted by the stylus  111 . 
     Optional step  3650 : decoding first data codes of received signals in accordance with the first PN code. If the electrical signals transmitted by the stylus  111  comprise the first data codes, the embedded processor  3440  of the touch sensitive processing apparatus  130  is able to decode the first data codes in accordance with the first PN code. Embodiments of the present application may include one or both of the steps  3640  and  3650 . 
     Optional step  3660 : despreading a second preamble code of received electrical signals in accordance with a second PN code. If the electrical signals transmitted by the stylus  111  comprise the second preamble code, the embedded processor  3440  of the touch sensitive processing apparatus  130  is able to despread the second preamble code in accordance with the first PN code. In some embodiments, the system  100  does not utilize the beacon signal to synchronize the timing of transmitting electrical signals, i.e., the steps  3610  and  3620  are omitted, the embedded processor  3440  may be required to use sliding window technique to acquire the second preamble code in the received electrical signals because the embedded processor  3440  has no idea when the electrical signals would be transmitted by the stylus  111 . 
     Optional step  3670 : decoding second data codes of received signals in accordance with the second PN code. If the electrical signals transmitted by the stylus  111  comprise the second data codes, the embedded processor  3440  of the touch sensitive processing apparatus  130  is able to decode the second data codes in accordance with the second PN code. Embodiments of the present application may include one or both of the steps  3660  and  3670 . 
     In order to save design complexity, the controller  3310  may encode the data codes reflecting status of onboard sensors in one of the signals  3311  and  3312 . Thus, it just needs to perform one of the steps  3650  and  3670  accordingly as well as the steps  3640  and  3660 . 
     In order to increase transmission reliability, the controller  3310  may encode the data codes in both of the signals  3311  and  3312 . The steps  3650  and  3670  may be performed accordingly to retrieve the first data codes and the second data codes. In one embodiment, the flow may further include a comparison step for comparing the first data codes and the second data codes. If these two data codes are inconsistent, the flow may drop out these two data codes because errors apparently happened in the transmission. However, in order to save design complexity, the flow may just include one of the steps  3650  and  3670  although the stylus  111  encode the data codes in both the signals  3311  and  3312 . 
     In the embodiments lacking of beacon signals, if the timing of electrical signals transmitted by the stylus  111  is found at steps  3640  or  3650 , the step  3660  and/or the step  3670  may be performed according to the found timing. In other words, the synchronization is built. Reversely, if the timing of electrical signals is found at steps  3660  or  3670 , the step  3640  and/or the step  3650  may be performed according to the found timing. In other words, in order to synchronize with the stylus  111 , the embedded processor  3440  just need to execute one sliding window algorithm to acquire one of the first and second preamble codes and the first and the second data codes. Otherwise, the steps  3640 - 3670  may be performed simultaneously or independently in an embodiment although sliding windows algorithms may be executed more than once. 
     Step  3680 : calculating a pressure according to signal strength ratio of a first part corresponding to the first PN code and a second part corresponding to the second PN code. The first part corresponding to the first PN code may be one or both of the first preamble code and the first data codes. Similarly, the second part corresponding to the second PN code may be one or both of the second preamble code and the second data codes. If the electrical signals comprise the first preamble code and the second preamble code, the step  3680  may be calculating the pressure reflecting to a pressure sensor of the stylus according to signal strength ratio of the first preamble code and the second preamble code. In case the electrical signals comprise the first data codes and the second data codes, the step  3680  may be calculating the pressure reflecting to a pressure sensor of the stylus according to signal strength ratio of the first data codes and the second data codes. In a variant, if the electrical signals comprise all four codes, the step  3680  may be calculating the pressure reflecting to a pressure sensor of the stylus according to signal strength ratio between the first part and the second part. Assume that the signal strength of the first part is M1 and the signal strength of the second part is M2, the ratio of these two signal strengths may be M1/M2, M2/M1, (M1−M2)/(M1+M2), (M2−M1)/(M1+M2), M1/(M1+M2), M2/(M1+M2) and any other calculations involving these two parameters M1 and M2. In order words, if the calculated ratio is a constant or a predetermined value, it is concluded that the pressure sensor of the stylus  111  does not sense any pressure. If the pressure sensor is configured to receive a pressure on the tip section  230  of the stylus  111 , it means that the tip section  230  of the stylus  111  does not touch anything including the touch panel  120 . 
     When the tip section  230  of the stylus  111  contacts the touch panel  120 , the tip section  230  is pressed to move. The first impedance Z1 of the first component  221  changes according to the movement or the pressure of the tip section  230  such that the ratio of M1 and M2 is varied accordingly from the constant or the predetermined value. The touch sensitive processing apparatus  130  could generate corresponding sensing (pressure) value according to the ratio. The afore-mentioned constant or predetermined value may not be a number but a range with a tolerable error. 
     By realizing well-known algorithm in the art, the touch sensitive processing apparatus  130  may calculate a position on the touch panel where the tip section  230  of the stylus  111  touching or approaching according to the electrical signals received by at least one of the first electrodes  121  and at least one of the second electrodes  122 . Thus, the position, the pressure, status of the onboard sensors and/or any other information of the stylus  111  may be received by the touch sensitive processing apparatus  130 . Consequently, the information received by the touch sensitive processing apparatus  130  may be forwarded to an operating system as well as application programs run on the host  140 . 
     Please refer to  FIG. 36B , which illustrates another flowchart diagram practiced by the embedded processor  3440  in accordance to an embodiment of the present invention. The flow is applicable to the touch sensitive processing apparatus  130  as shown in  FIGS. 33 and 34 . Unless a causal relationship is noted, the present invention does not limit execution sequences of any two of the steps as shown in  FIG. 36B . If a beacon signal is used as a synchronization signal in the system  100 , the flow begins with the step  3610 . 
     The differences between the flowcharts as shown in  FIGS. 36A and 36B  are the steps  3630  through  3670  are replaced by the steps  3210  through  3250  as described in  FIG. 32 . One of the purposes of the flow  3200  is to accelerate the acquisition of preamble codes of one or more styli by coupling at least two of the second electrodes as a synchronization channel. In other words, the touch sensitive processing apparatus  130  is configured to synchronize the stylus without the beacon signal mechanism. Although the flow illustrated in  FIG. 36B  comprises optional steps  3610  and  3620 , these two steps may also serve in a touch sensitive system  100  which comprises at least one stylus  111  which listens to the beacon signal while other stylus  111  does not synchronize the beacon signal. In other words, the touch sensitive processing apparatus  130  may be configured to operate with different styli  111  which may or may not have beacon signal receiver simultaneously. Although it demands more processing capability and more memory space for storing electrical signals to the touch sensitive processing apparatus  130 , the interoperability of such touch system  100  is increased significantly. 
     By comparing the timing of transmitting the electrical signals and the turnaround time period indicated in the beacon signal, the touch sensitive processing apparatus  130  may detect one stylus  111  having no beacon signal synchronization capability because the timing is inconsistent with the indicated turnaround time period. 
     If the touch system  100  comprises a stylus  111  having beacon signal synchronization capability and another stylus  111  having no such capability, the touch sensitive processing apparatus  130  may adjust the timing of the beacon signal and/or the turnaround time period indicated in the beacon signal to have these two styli  111  transmitting their electrical signals simultaneously so as to minimize the time period spent in the receiving electrical signals from the styli  111  and to maximize the time period for detecting external conductive objects such as fingers. Alternatively, the touch sensitive processing apparatus  130  may adjust the timing of the beacon signal and/or the turnaround time period indicated in the beacon signal to have these two styli  111  transmitting their electrical signals in non-overlapping periods so as to minimize the interferences between the two electrical signals. Moreover, since the electrical signal emitted by the stylus can interfere with the reception of the beacon signal, the touch sensitive processing apparatus  130  may adjust the timing of the beacon signal and/or the turnaround time period indicated in the beacon signal to alleviate or to eliminate the interference between the beacon signal and the electrical signal transmitted from the stylus. 
     In the embodiments as shown in  FIGS. 35, 36A and 36B , two PN codes is assigned to each of the stylus  111 . Hence, the touch sensitive processing apparatus  130  is able to identify all styli  111  which transmit electrical signals simultaneously. However, unlike the touch sensitive processing apparatus  130 , computing resources and internal space of the stylus  111  is quite limited. It may be desired to decrease computing complexity of the controller  3310 . Hence, the controller  3310  of the stylus  111  as shown in  FIG. 33  may transmit the same electrical signals  3311  and  3312  encoded by one PN code in two different time periods, respectively. As long as each stylus  111  in one touch system  100  has different PN code, the touch sensitive processing apparatus  130  is able to identify all styli  111  which may transmit electrical signals simultaneously. With regard to electrical signals from the same stylus  111  in two different time periods, the touch sensitive processing apparatus  130  is able to calculate a pressure according to signal strength ratio of these two time periods. Furthermore, the controller  3310  may collect status of the onboard sensors of the stylus  111  twice to generate two data codes before transmitting them through the tip section  230 . By decreasing the number of PN codes from two to one, the design complexity of the controller  3310  is reduced consequently. 
     Please refer to  FIG. 37A , which illustrates a flowchart diagram practiced by the controller  3310  as shown in  FIG. 33  in accordance to an embodiment of the present invention. The flow may be also applicable to the stylus  111  as shown in  FIG. 33 . Unless a causal relationship is noted, the present invention does not limit execution sequences of any two of the steps as shown in  FIG. 37A . Steps  3520 ,  3530  and  3540  are explained above in the paragraphs regarding to the flowchart as shown in  FIG. 35 . 
     Optional step  3710 : receiving configuration setting of a PN code. The configuration mechanism is already described. 
     Step  3750 : transmitting a preamble code and/or data codes according to the PN code to a first component having variable impedance reflecting a pressure in a first time period. The transmitted signal may be the preamble code, the data codes, or both of them. Since they are all encoded by the assigned PN code, the touch sensitive processing apparatus  130  is able to detect and decode the transmitted signals via the tip section  230  and the electrodes  121  and/or  122  in the first time period. 
     Step  3760 : transmitting the preamble code and/or data codes according to the PN code to a second component having fixed impedance in a second time period. The transmitted signal may be the preamble code, the data codes, or both of them. Since they are all encoded by the assigned PN code, the touch sensitive processing apparatus  130  is able to detect and decode the transmitted signals via the tip section  230  and the electrodes  121  and/or  122  in the second time period. 
     In one embodiment, a turnaround time period between the first time period and the second time period may exist. During this turnaround timer period, the controller  3310  may switch signal output from the first component  221  to the second component  222 . 
     Please refer to  FIG. 37B , which illustrates another flowchart diagram practiced by the controller  3310  as shown in  FIG. 33  in accordance to an embodiment of the present invention. The flow may be also applicable to the stylus  111  as shown in  FIG. 33 . Unless a causal relationship is noted, the present invention does not limit execution sequences of any two of the steps as shown in  FIG. 37B . 
     Optional step  3745 : generating first data codes according to status of onboard sensors. If the stylus  111  comprises one or more onboard sensors such as button, switch, knob, battery volume and etc. in additional to the pressure sensor connected to the first component  221 , data codes may be generated to reflect the status of onboard sensors and/or other information such as the identification of the stylus  111 , and/or model and vendor name of the stylus  111 . 
     Step  3755 : transmitting a preamble code and/or first data codes according to the PN code to a first component having variable impedance reflecting a pressure in a first time period. The transmitted signal may be the preamble code, the first data codes, or both of them. Since they are all encoded by the assigned PN code, the touch sensitive processing apparatus  130  is able to detect and decode the transmitted signals via the tip section  230  and the electrodes  121  and/or  122  in the first time period. After step  3755 , the flow may go to optional step  3746  for generating another data codes. 
     Optional step  3746 : generating second data codes according to status of onboard sensors. 
     Step  3765 : transmitting the preamble code and/or second data codes according to the PN code to a second component having fixed impedance in a second time period. The transmitted signal may be the preamble code, the second data codes, or both of them. Since they are all encoded by the assigned PN code, the touch sensitive processing apparatus  130  is able to detect and decode the transmitted signals via the tip section  230  and the electrodes  121  and/or  122  in the second time period. 
     Although in the flowchart as shown in  FIG. 37A , the flow executes the step  3750  before the step  3760 . Persons having ordinary skill in the art can understand that the sequence of steps  3750  and  3760  may be reversed. The flow may go to the step  3760  from the step  3540  in some embodiments. Then the flow may go to the step  3750  after the step  3760 . Similarly, in the flowchart as shown in  FIG. 37B , the flow may go to the steps  3746  and  3765  from the step  3530 . Then the flow may go to the steps  3745  and  3755  after the step  3765 . In short, the present invention does not require which one of the signals  3311  and  3312  is first sent out from the controller  3310 . 
     Please refer to  FIG. 38A , which illustrates a flowchart diagram practiced by the embedded processor  3440  in accordance to an embodiment of the present invention. Adapting to the flowcharts embodied by one or more styli  111  as shown in  FIGS. 37A and 37B , the flow is applicable to the touch sensitive processing apparatus  130  as shown in  FIGS. 33 and 34 . Unless a causal relationship is noted, the present invention does not limit execution sequences of any two of the steps as shown in  FIG. 38A . If a beacon signal is used as a synchronization signal in the system  100 , the flow begins with the step  3610 . Two steps  3610  and  3620  are described in the paragraphs with regard to the embodiment as shown in  FIG. 36A . The flow may go to step  3830  after step  3620  is executed. 
     Step  3830 : receiving electrical signals via electrodes of a touch panel in a first and a second time periods. The step  3830  may be performed concurrently with any of the steps  3850  through  3870  during the second time period. The electrical signals are received by the sensing circuit  3430  of the touch sensitive processing apparatus  130  via the electrodes near the tip section  230 . The electrical signals received in two different time periods are stored, respectively. 
     Optional step  3840 : despreading a first preamble code of electrical signals received in the first time period in accordance with a PN code. If the electrical signals transmitted by the stylus  111  comprise the first preamble code, the embedded processor  3440  of the touch sensitive processing apparatus  130  is able to despread the first preamble code in accordance with the PN code. In some embodiments, the system  100  does not utilize the beacon signal to synchronize the timing of transmitting electrical signals, i.e., the steps  3610  and  3620  are omitted, the embedded processor  3440  may be required to use sliding window technique to acquire the preamble code in the received electrical signals because the embedded processor  3440  has no idea when the electrical signals would be transmitted by the stylus  111 . 
     Optional step  3850 : decoding first data codes of electrical signals received in the first time period in accordance with the PN code. If the electrical signals transmitted by the stylus  111  comprise the first data codes, the embedded processor  3440  of the touch sensitive processing apparatus  130  is able to decode the first data codes in accordance with the PN code corresponding to the stylus  111 . Embodiments of the present application may include one or both of the steps  3840  and  3850 . 
     Optional step  3860 : despreading a second preamble code of electrical signals received in the second time period in accordance with a PN code. If the electrical signals transmitted by the stylus  111  comprise the second preamble code, the embedded processor  3440  of the touch sensitive processing apparatus  130  is able to despread the second preamble code in accordance with the PN code. Please be aware that since the first and the second preamble codes are encoded by the same PN code, they should be the same if their signal strengths are disregarded. In some embodiments, the system  100  does not utilize the beacon signal to synchronize the timing of transmitting electrical signals, i.e., the steps  3610  and  3620  are omitted, the embedded processor  3440  may be required to use sliding window technique to acquire the preamble code in the received electrical signals because the embedded processor  3440  has no idea when the electrical signals would be transmitted by the stylus  111 . 
     Optional  3870 : decoding second data codes of electrical signals received in the second time period in accordance with the PN code. If the electrical signals transmitted by the stylus  111  comprise the second data codes, the embedded processor  3440  of the touch sensitive processing apparatus  130  is able to decode the second data codes in accordance with the PN code corresponding to the stylus  111 . Embodiments of the present application may include one or both of the steps  3860  and  3870 . 
     As described in the embodiment as shown in  FIG. 37B , the controller  3310  may generate two data codes for the two transmissions in the two time periods. If the first data codes are different from the data codes, it tells that the status of the onboard sensors was changed between the two generations. Apparently, the positions of the stylus  111  may also change between the two generations. Therefore the touch sensitive processing apparatus  130  may calculate a first position and a second position according to the electrical signals received during the first time period and the second time period accordingly. Or the touch sensitive processing apparatus  130  may calculate only one position according to either one of the electrical signals received during the first time period or received during the second time period. 
     Step  3880 : calculating a pressure according to signal strength ratio of a first part received in the first time period and a second part received in the second time period. The first part of electrical signals received in the first time period may be one or both of the first preamble code and first data codes. Similarly, the second part of electrical signals received in the second time period may be one or both of the second preamble code and second data codes. If the electrical signals comprise the first preamble code and the second preamble code, the step  3880  may be calculating the pressure reflecting to a pressure sensor of the stylus according to signal strength ratio of the first preamble code and the second preamble code. In case the electrical signals comprise the first data codes and the second data codes, the step  3880  may be calculating the pressure reflecting to a pressure sensor of the stylus according to signal strength ratio of the first data codes and the second data codes. In a variant, if the electrical signals comprise all four codes, the step  3880  may be calculating the pressure reflecting to a pressure sensor of the stylus according to signal strength ratio between the first part received in the first time period and the second part received in the second time period. Assume that the signal strength of the first part is M1 and the signal strength of the second part is M2, the ratio of these two signal strengths may be M1/M2, M2/M1, (M1−M2)/(M1+M2), (M2−M1)/(M1+M2), M1/(M1+M2), M2/(M1+M2) and any other calculations involving these two parameters M1 and M2. In order words, if the calculated ratio is a constant or a predetermined value, it is concluded that the pressure sensor of the stylus  111  does not sense any pressure. If the pressure sensor is configured to receive a pressure on the tip section  230  of the stylus  111 , it means that the tip section  230  of the stylus  111  does not touch anything including the touch panel  120 . 
     Please refer to  FIG. 38B , which illustrates a flowchart diagram practiced by the embedded processor  3440  in accordance to an embodiment of the present invention. Adapting to the flowcharts embodied by one or more styli  111  as shown in  FIGS. 37A and 37B , the flow is applicable to the touch sensitive processing apparatus  130  as shown in  FIGS. 33 and 34 . Unless a causal relationship is noted, the present invention does not limit execution sequences of any two of the steps as shown in  FIG. 38B . If a beacon signal is used as a synchronization signal in the system  100 , the flow begins with the step  3610 . Two steps  3610  and  3620  are described in the paragraphs with regard to the embodiment as shown in  FIG. 36B . The flow may go to step  3210  after step  3620  is executed. 
     Optional step  3815 : despreading a first preamble code of a first signal frame of received in a first timer period from the synchronization channel to retrieve a first synchronization information according to a pseudo noise code. 
     Optional step  3825 : decoding first data codes behind the first preamble code of electrical signal received in the first time period from at least one of the first electrodes in accordance with the first synchronization information and the PN code. 
     Optional step  3835 : despreading a second preamble code of a second signal frame of received in a second timer period from the synchronization channel to retrieve a second synchronization information according to the PN code. 
     Optional step  3845 : decoding second data codes behind the second preamble code of electrical signal received in the second time period from at least one of the first electrodes in accordance with the second synchronization information and the PN code. 
     In an embodiment, once the first synchronization information with regard to the first time period is known, the second synchronization information could be calculated accordingly. 
     In an embodiment, Please be aware that since the first and the second preamble codes are encoded by the same PN code, they should be the same if their signal strengths are disregarded. In some embodiments, the system  100  does not utilize the beacon signal to synchronize the timing of transmitting electrical signals, i.e., the steps  3610  and  3620  are omitted, the embedded processor  3440  may be required to use sliding window technique to acquire the preamble code in the received electrical signals because the embedded processor  3440  has no idea when the electrical signals would be transmitted by the stylus  111 . 
     As described in the embodiment as shown in  FIG. 37B , the controller  3310  may generate two data codes for the two transmissions in the two time periods. If the first data codes are different from the data codes, it tells that the status of the onboard sensors was changed between the two generations. Apparently, the positions of the stylus  111  may also change between the two generations. Therefore the touch sensitive processing apparatus  130  may calculate a first position and a second position according to the electrical signals received during the first time period and the second time period accordingly. Or the touch sensitive processing apparatus  130  may calculate only one position according to either one of the electrical signals received during the first time period or received during the second time period. 
     Step  3880 : calculating a pressure according to signal strength ratio of a first part received in the first time period and a second part received in the second time period. The first part may be one or both of the first preamble code and the first data codes. Similarly, the second part may be one or both of the second preamble code and the second data codes. If the electrical signals comprise the first preamble code and the second preamble code, the step  3880  may be calculating the pressure reflecting to a pressure sensor of the stylus according to signal strength ratio of the first preamble code and the second preamble code. In case the electrical signals comprise the first data codes and the second data codes, the step  3880  may be calculating the pressure reflecting to a pressure sensor of the stylus according to signal strength ratio of the first data codes and the second data codes. In a variant, if the electrical signals comprise all four codes, the step  3880  may be calculating the pressure reflecting to a pressure sensor of the stylus according to signal strength ratio between the first part received in the first time period and the second part received in the second time period. Assume that the signal strength of the first part is M1 and the signal strength of the second part is M2, the ratio of these two signal strengths may be M1/M2, M2/M1, (M1−M2)/(M1+M2), (M2−M1)/(M1+M2), M1/(M1+M2), M2/(M1+M2) and any other calculations involving these two parameters M1 and M2. In order words, if the calculated ratio is a constant or a predetermined value, it is concluded that the pressure sensor of the stylus  111  does not sense any pressure. If the pressure sensor is configured to receive a pressure on the tip section  230  of the stylus  111 , it means that the tip section  230  of the stylus  111  does not touch anything including the touch panel  120 . 
     In real word scenarios, it is not uncommon to get lost of a wireless stylus  111 . Besides, it may need to recharge battery of the wireless stylus  111  quite often. In some scenarios, it is desired to have one or more corded styli which physically connect to the touch system. Utilizing the same mechanism of PN codes, the touch sensitive processing apparatus can select its own timing to transmit signals to corded stylus and to receive the signals from the touch panel  120 . This mechanism is able to omit the synchronization mechanism between the wireless stylus  111  and the touch sensitive processing apparatus  130 . 
     Please refer to  FIG. 39A , which illustrates a schematic diagram of a touch system  3900  in accordance with an embodiment of the present invention. The touch system  3900  may comprises the touch panel  120 , the touch sensitive processing apparatus  130 , the host  140 , and a corded stylus  3910 . The corded stylus  3910  may comprises the first component  221  with variable first impedance Z1 which reflects to a pressure to the first component  221 , the second component  222  with fixed second impedance Z2, the tip section  230  which is coupled to the outputs of the first component  221  and the second component  222 , and a shell or a container which encapsulates the first component  221 , the second component  222  and the tip section  230 . A cord is used to connect the stylus  3910  and the touch sensitive processing apparatus  130 . The cord may be a twisted and shielded cable which may include a first signal circuit  3911 , a second signal circuit  3912 , and a third circuit  3913 . In one embodiment, the third line  3913  may be electrically coupled to the shell which may be grounded if a user holds the stylus  3910  by hand. In addition, the third line  3913  may be electrically coupled to a ground potential port of the touch sensitive processing apparatus  130 . 
     Although there is only one corded stylus  3910  shown in  FIG. 39A , there may be multiple corded styli  3910  connecting to the touch sensitive processing apparatus  130  in some embodiments of the present invention. Based on the proposed mechanism, the multiple corded styli  3910  can operate simultaneously. More importantly, a touch system of embodiments in accordance with the present invention may comprise wireless and corded styli. Persons having ordinary skill art can understand the touch sensitive processing apparatus  130  may use the synchronization mechanism to have the wireless stylus  111  transmit electrical signals at the same time while the touch sensitive processing apparatus  130  transmits electrical signals via the corded stylus  3910  if the electrical signals simultaneously transmitted from each of the wireless and corded styli are encoded by different sets of PN codes. 
     The corded stylus  3910  as shown in  FIG. 39A  does not include a switch or a button. However, a corded stylus  3910  may comprise one or more onboard sensors such as a switch or a button for receiving user&#39;s input. In one embodiment, each of the onboard sensors may connect to the touch sensitive processing apparatus  130  via one or more circuits included in the cord. Hence, the status of the onboard sensor may be detected by the touch sensitive processing apparatus  130  via the cord. For example, the touch sensitive processing apparatus  130  may detect whether an eraser button is pressed or not via one or more circuits connecting to the eraser button. However, just similar to the embodiments as shown in  FIGS. 4A and 4B , the corded stylus  3910  may further comprise a switch and a corresponding component which is connected in parallel with the first or the second components. The touch sensitive processing apparatus  130  is able to tell the status of the switch of the stylus  3910  according to a ratio of signal strength between the two PN codes. 
     Please refer to  FIG. 39B , which illustrates a schematic diagram of a variant of the touch system  3900  in accordance with an embodiment of the present invention. The stylus  3910  may further comprise a third switch  3920  and a third component  3930  which are connected in parallel to the first component  221 . The third component  3930  may be a circuit such as a resistance and/or a capacitor with third impedance Z3. When the third switch  3920  is closed by a user of the stylus  3910 , the signal driven by the signal circuit  3911  propagates through the first component  221  and the third component  3930  to the tip section  230 . Reversely, when the third switch  3920  is opened by the user, the signal driven by the signal circuit  3911  propagates through the first component  221  to the tip section  230 . The signal driven by the signal circuit  3912  propagates through the second component  222  to the tip section  230 . After receiving the signals driven by the signal circuits  3911  and  3912  emitted from the tip section  230 , the touch sensitive processing apparatus  130  is able to tell the status of the third switch  3920  of the stylus  3910  according to a ratio of signal strength between the two signals driven by the signal circuits  3911  and  3912 . If the ratio is fallen into a first interval, the touch sensitive processing apparatus  130  determines that the third switch  3920  is being opened. If the ratio is fallen into a second interval, the touch sensitive processing apparatus  130  determines that the third switch  3920  is being closed. The third impedance characteristics of the third component  3930  may be configured such that the first interval is not interleaved with the second interval. Moreover, the touch sensitive processing apparatus  130  may be able to calculate the pressure on the first component  221  according to the ratio which may be fallen into the first interval or the second interval. 
     Please refer back to  FIG. 4A . The active stylus  110  comprises two switches SWE and SWB, the eraser capacitor  441  corresponding to the switch SWE and the barrel capacitor  442  corresponding to the switch SWB. They are arranged in parallel with the first capacitor  321 . Although the corded stylus  3910  as shown in  FIG. 39B  comprises only one third switch  3920  and one corresponding third component  3930 , persons with ordinary skill in the art may understand that the corded stylus  3910  may have more than one set of third switch  3920  and corresponding third component  3930  which are arranged in parallel with the first component  221 . 
     Please refer to  FIG. 39C , which illustrates a schematic diagram of a variant of the touch system  3900  in accordance with an embodiment of the present invention. The stylus  3910  may further comprise a fourth switch  3940  and a fourth component  3950  which are connected in parallel to the second component  222 . The fourth component  3950  may be a circuit such as a resistance and/or a capacitor with fourth impedance Z4. When the fourth switch  3940  is closed by a user of the stylus  3910 , the signal driven by the signal circuit  3912  propagates through the second component  222  and the fourth component  3950  to the tip section  230 . Reversely, when the fourth switch  3940  is opened by the user, the signal driven by the signal circuit  3912  propagates through the second component  222  to the tip section  230 . The signal driven by the signal circuit  3911  propagates through the first component  221  to the tip section  230 . After receiving the signals driven by the signal circuit  3911  and  3912  emitted from the tip section  230 , the touch sensitive processing apparatus  130  is able to tell the status of the fourth switch  3940  of the stylus  3910  according to a ratio of signal strength between the two signals driven by the signal circuit  3911  and  3912 . If the ratio is fallen into a third interval, the touch sensitive processing apparatus  130  determines that the fourth switch  3940  is being opened. If the ratio is fallen into a fourth interval, the touch sensitive processing apparatus  130  determines that the fourth switch  3940  is being closed. The fourth impedance characteristics of the fourth component  3950  may be configured such that the third interval is not interleaved with the fourth interval. Moreover, the touch sensitive processing apparatus  130  may be able to calculate the pressure on the first component  221  according to the ratio which may be fallen into the third interval or the fourth interval. 
     Please refer back to  FIG. 4B . The active stylus  110  comprises two switches SWE and SWB, the eraser capacitor  441  corresponding to the switch SWE and the barrel capacitor  442  corresponding to the switch SWB. They are arranged in parallel with the second capacitor  322 . Although the corded stylus  3910  as shown in  FIG. 39C  comprises only one fourth switch  3940  and one corresponding fourth component  3960 , persons with ordinary skill in the art may understand that the corded stylus  3910  may have more than one set of fourth switch and corresponding fourth component which are arranged in parallel with the second component  222 . 
     In one embodiment, the touch sensitive processing apparatus  130  may concurrently transmits the signals via the signal circuits  3911  and  3912  to the stylus  3910  which are encoded according to a first PN code and a second PN code, respectively. Therefore, the touch sensitive processing apparatus  130  may receive the signals driven by the signal circuits  3911  and  3912  from the touch panel  120  concurrently. In another embodiment, the touch sensitive processing apparatus  130  may transmits the signals via the signal circuits  3911  and  3912  to the stylus  3910  which are encoded according to one PN code in a time-sharing manner. Therefore, the touch sensitive processing apparatus  130  may receive the signals driven by the signal circuits  3911  and  3912  from the touch panel  120  in two time periods, respectively. In both embodiments, the touch sensitive processing apparatus  130  may be able to determine the status of the third switch  3920  or the fourth switch  3940  according to the ratio of the signals driven by the signal circuits  3911  and  3912 . Moreover, the touch sensitive processing apparatus  130  may be able to calculate the pressure on the first component  221  according to the ratio of the signals driven by the signal circuits  3911  and  3912 . 
     Please refer to  FIG. 40 , which depicts a schematic diagram of a touch sensitive processing apparatus  130  in accordance with an embodiment of the invention. Comparing with the touch sensitive processing apparatus  130  as shown in  FIG. 34 , the touch sensitive processing apparatus  130  further comprise one or more stylus interface  4010  which is coupled to the interconnection network  3410 . The stylus interface  4010  may be compatible to existing industrial standard or a proprietary interface which includes three circuits  3911 ,  3912  and  3913  corresponding to one of the stylus  3910 . For one stylus  3910 , there is one corresponding stylus interface  4010 . 
     The touch sensitive processing apparatus  130  may further include an embedded processor  4040  which is configured to generate signals encoded by one or more pseudo-random number codes corresponding to each stylus  3910 . The generated signals may be sent to the driving circuit  3420  for front-end analog processing. And the interconnection network  3410  is further configured by the embedded processor  4040  to selectively connect the driving circuit  3420  to at least one of the signal circuits  3911  and  3912 . Therefore the signals encoded by PN code is transmitted to the tip section  230  of the corresponding stylus  3910  which connects to the stylus interface  4010 . 
     Moreover, the interconnection network  3410  is further configured by the embedded processor  4040  to connect the sensing circuit  3430  and the electrodes of the touch panel  120 . If the tip section  230  of the corresponding stylus  3910  is placed on or near the touch panel, the signals emitted by the tip section  230  would be received by the sensing circuit  3430  via the electrodes of the touch panel  120 . After doing front-end analog processing and analog-to-digital conversion, the embedded processor  4040  receives the signals from the sensing circuit  3430 . Person having ordinary skill in the art can understand that the embedded processor  4040  is able to calculate the received signal strengths corresponding to the signals sent to the signal circuits  3911  and  3912 , respectively, according to the received signals. Thus, a ratio of the signal strength can be calculated accordingly. As explained in previous paragraphs, based on the received signals and the ratio, the embedded processor  4040  may be able to determine three parameters: the pressure received by the stylus  3910 ; the status of a switch of the stylus  3910 ; and a position where the tip section  230  of the stylus  3910  touching or approaching the touch panel  120 . 
     Please refer to  FIG. 41A , which illustrates a flowchart diagram of an operating method applicable to a corded stylus of an embodiment according to the invention. The flowchart is especially applicable to the corded stylus  3910  as shown in  FIG. 39A . Unless a causal relationship is noted, the present invention does not limit execution sequences of any two of the steps as shown in  FIG. 41A . 
     Step  4110 : receiving a first preamble code according to a first PN code by a first component having variable impedance reflecting a pressure. As shown in  FIG. 39A , the first component  221  of the stylus  3910  receives the first preamble code via the signal circuit  3911 . 
     Step  4120 : receiving a second preamble code according to a second PN code by a second component having fixed impedance. As shown in  FIG. 39A , the second component  222  of the stylus  3910  receives the second preamble code via the signal circuit  3912 . The steps  4110  and  4120  may be being performed concurrently or in a time-sharing manner. 
     Step  4130 : transmitting the first preamble code by the first component to a tip section. 
     Step  4140 : transmitting the second preamble code by the second component to the tip section. If the steps  4110  and  4120  are being performed concurrently, the steps  4130  and  4140  are also being performed concurrently. Or, all these four steps  4110  through  4140  are being performed concurrently. 
     If the touch sensitive processing apparatus  130  connects to multiple styli  3910 , a set of two PN codes can be assigned to each stylus  3910 . For example, a set including a first PN code and a second PN code is assigned to a first corded stylus  3910  and another set including a third PN code and a fourth PN code is assigned to a second corded stylus  3910 . The flowchart diagram as shown in  FIG. 41A  is applicable to the first and the second corded styli  3910 . In other words, two corded styli  3910  can operate on one touch panel  120  concurrently. 
     Please refer to  FIG. 41B , which illustrates a flowchart diagram of an operating method applicable to a corded stylus of an embodiment according to the invention. The flowchart is especially applicable to the corded stylus  3910  as shown in  FIG. 39B . Unless a causal relationship is noted, the present invention does not limit execution sequences of any two of the steps as shown in  FIG. 41B . Because the corded stylus  3910  as shown in  FIG. 39B  comprises the third switch  3920  and the third component  3930 , the flowchart further comprises steps  4122  and  4124 . 
     Step  4122 : selectively receiving the first preamble code by a third component which is connected in parallel with the first component. The selectively receiving is carried out by the third switch  3920  as shown in  FIG. 39B . 
     Step  4124 : selectively transmitting the first preamble code by the third component to a tip section. The selective transmitting is also carried out by the third switch  3920  as shown in  FIG. 39B . The steps  4110 ,  4120 ,  4122  and  4124  may be being performed concurrently. 
     Please refer to  FIG. 41C , which illustrates a flowchart diagram of an operating method applicable to a corded stylus of an embodiment according to the invention. The flowchart is especially applicable to the corded stylus  3910  as shown in  FIG. 39C . Unless a causal relationship is noted, the present invention does not limit execution sequences of any two of the steps as shown in  FIG. 41C . Because the corded stylus  3910  as shown in  FIG. 39C  comprises the fourth switch  3940  and the fourth component  3950 , the flowchart further comprises steps  4126  and  4128 . 
     Step  4126 : selectively receiving the second preamble code by a fourth component which is connected in parallel with the second component. The selectively receiving is carried out by the fourth switch  3940  as shown in  FIG. 39C . 
     Step  4128 : selectively transmitting the second preamble code by the fourth component to a tip section. The selective transmitting is also carried out by the fourth switch  3940  as shown in  FIG. 39C . The steps  4110 ,  4120 ,  4126  and  4128  may be being performed concurrently. 
     Please refer to  FIG. 42 , which depicts a flowchart diagram applicable to a touch sensitive processing apparatus  130  according to an embodiment of the present invention. The flowchart may be applicable to the touch sensitive processing apparatus  130  as shown in  FIG. 40  for controlling a corded stylus  3910  as shown in  FIGS. 41A-41C . For instance, the flowchart may be implemented as instructions for being executed by the embedded processor  4040  of the touch sensitive processing apparatus  130 . Unless a causal relationship is noted, the present invention does not limit execution sequences of any two of the steps as shown in  FIG. 42 . The steps  3630 ,  3640 ,  3660  and  3680  included in this flowchart are already explained in the embodiment as shown in  FIGS. 36A and 36B . 
     Step  4210 : transmitting a first preamble code according to a first PN code to a first circuit of a stylus. For example, the first preamble code is generated by the embedded processor  4040 , processed by the driving circuit  3420 , transmitted by the stylus interface  4010  to the signal circuit  3911 . 
     Step  4220 : transmitting a second preamble code according to a second PN code to a second circuit of the stylus. For example, the second preamble code is generated by the embedded processor  4040 , processed by the driving circuit  3420 , transmitted by the stylus interface  4010  to the signal circuit  3912 . The steps  4210  and  4220  may be being executed concurrently. 
     Optional step  4290 : calculating a switch status of the stylus according to signal strength ratio of the first part and the second part of the electrical signals. 
     Please refer to  FIG. 43 , which depicts a flowchart diagram applicable to a touch sensitive processing apparatus  130  according to an embodiment of the present invention. The flowchart may be applicable to the touch sensitive processing apparatus  130  as shown in  FIG. 40  for controlling a corded stylus  3910  as shown in  FIGS. 41A-41C . For instance, the flowchart may be implemented as instructions for being executed by the embedded processor  4040  of the touch sensitive processing apparatus  130 . Unless a causal relationship is noted, the present invention does not limit execution sequences of any two of the steps as shown in  FIG. 43 . The step  3880  is already explained in the embodiment as shown in  FIGS. 38A and 38B . Besides, the optional step  4290  is also explained in the embodiment as shown in  FIG. 42 . 
     Step  4310 : transmitting a first preamble code according to a first PN code to a first circuit of a stylus in a first time period. 
     Step  4320 : receiving electrical signals via electrodes of a touch panel in the first time period. 
     Step  4330 : despreading the first preamble code of electrical signals received in the first time period in accordance with the first PN code. 
     Step  4340 : transmitting a second preamble code according to a second PN code to a second circuit of the stylus in a second time period. The first time period may be completely separated from the second time period. Alternatively, part of the second time period may be concurrent with part of the first time period. 
     Step  4350 : receiving electrical signals via electrodes of a touch panel in the second time period. 
     Step  4360 : despreading the second preamble code of electrical signals received in the second time period in accordance with the second PN code. 
     Please refer to  FIG. 44 , which depicts a flowchart diagram applicable to a touch sensitive processing apparatus  130  according to an embodiment of the present invention. The flowchart may be applicable to the touch sensitive processing apparatus  130  as shown in  FIG. 40  for controlling a corded stylus  3910  as shown in  FIGS. 41A-41C . For instance, the flowchart may be implemented as instructions for being executed by the embedded processor  4040  of the touch sensitive processing apparatus  130 . Unless a causal relationship is noted, the present invention does not limit execution sequences of any two of the steps as shown in  FIG. 44 . The steps  4320  and  4350  are explained in the embodiment as shown in  FIG. 43 . The step  3880  is already explained in the embodiment as shown in  FIGS. 38A and 38B . Besides, the optional step  4290  is also explained in the embodiment as shown in  FIG. 42 . 
     Step  4410 : transmitting a first preamble code according to a PN code to a first circuit of a stylus in a first time period. 
     Step  4430 : despreading the first preamble code of electrical signals received in the first time period in accordance with the PN code. 
     Step  4440 : transmitting a second preamble code according to the PN code to a second circuit of the stylus in a second time period. 
     Step  4460 : despreading the second preamble code of electrical signals received in the second time period in accordance with the PN code. 
     One object of the present invention is to provide a stylus for transmitting electrical signals carrying pressure information, comprising: a first component with variable impedance reflecting a pressure, wherein the first component is configured for receiving first signals encoded by a first pseudo-random number (PN) code; a second component with fixed impedance, wherein the second component is configured for receiving second signals encoded by a second PN code; and a conductive tip section configured for: receiving, simultaneously, the first signals from the first component and the second signals from the second component; and transmitting electrical signals which is composed of the first signals and the second signals, wherein the first PN code is orthogonal to the second PN code. 
     In one embodiment, in order to provide the first PN code and the second PN code onboard the stylus, the stylus further comprises a controller, configured for: generating the first signals according to the first PN code; generating the second signals according the second PN code; transmitting the first signals to the first component; and transmitting the second signals to the second component. 
     In one embodiment, in order to transmit status of onboard sensor of the stylus, the stylus further comprises: at least one onboard sensor coupled to the controller. The controller is further configured for: generating data codes according to status of the at least one onboard sensor; generating first data codes according to the data codes and the first PN code; and transmitting the first data codes to the first component. The first component is further configured for receiving the first data codes from the controller. The conductive tip section is further configured for: receiving the first data codes from the first component; and transmitting the first data codes. 
     In one embodiment, in order to transmit status of onboard sensor of the stylus, the stylus further comprises: at least one onboard sensor coupled to the controller. The controller is further configured for: generating data codes according to status of the at least one onboard sensor; generating second data codes according to the data codes and the second PN code; and transmitting the second data codes to the second component. The second component is further configured for receiving the second data codes from the controller. The conductive tip section is further configured for: receiving the second data codes from the second component; and transmitting the second data codes. 
     In one embodiment, in order to synchronize with receiving procedure of a touch sensitive processing apparatus of a touch panel, the controller is further configured for: receiving a synchronization signal from an electronic device; and after the synchronization signal is received, executing the generating steps and the transmitting steps. 
     In one embodiment, in order to synchronize with receiving procedure of the touch sensitive processing apparatus of the touch panel where the stylus touches or approximates, the controller is coupled to the conductive tip section for receiving the synchronization signal which is being transmitted from electrodes of a touch panel of the electronic device. 
     In one embodiment, in order to prevent conflicts of PN codes when multiple styli operate with one touch panel, the stylus further comprises a human-machine interface for user&#39;s input of PN codes, wherein the controller is further configured for receiving a setting instruction from the human-machine interface for designating a set of the first PN code and the second PN code. 
     In one embodiment, in order to provide PN code setting information to user, the stylus further comprises at least one of following device coupled to the controller for indicating a set of the first PN code and the second PN code: a visual indicator; and an audio indicator. 
     In one embodiment, in order to provide a wire connection between the corded or tethered stylus and a touch sensitive processing apparatus, the stylus further comprises: a first signal circuit, coupled to the first component and a touch sensitive processing apparatus, configured for propagating the first signals from the touch sensitive processing apparatus to the first component; and a second signal circuit, coupled to the second component and the touch sensitive processing apparatus, configured for propagating the second signals from the touch sensitive processing apparatus to the second component. 
     In one embodiment, in order to provide a switch status to a touch sensitive processing apparatus, the stylus further comprises a third switch configured for receiving the first signals; and a third component with fixed impedance, coupled to the third switch and the conductive tip section, wherein the third switch is selectively being opened or closed, the first signals are propagated through the third switch and the third component to the conductive tip section when the third switch is being closed. 
     In one embodiment, in order to provide a switch status to a touch sensitive processing apparatus, the stylus further comprises a fourth switch configured for receiving the second signals; and a fourth component with fixed impedance, coupled to the fourth switch and the conductive tip section, wherein the fourth switch is selectively being opened or closed, the second signals are propagated through the fourth switch and the fourth component to the conductive tip section when the fourth switch is being closed. 
     One object of the present invention is to provide a method for transmitting electrical signals carrying pressure information from a stylus, comprising: receiving, by a first component with variable impedance reflecting a pressure, first signals encoded by a first PN code; receiving, by a second component with fixed impedance, second signals encoded by a second PN code; receiving, simultaneously, the first signals from the first component and the second signals from the second component by a conductive tip section; and transmitting electrical signals which is composed of the first signals and the second signals by the conductive tip section, wherein the first PN code is orthogonal to the second PN code. 
     In one embodiment, in order to provide the first PN code and the second PN code onboard the stylus, the method further comprises: generating the first signals according to the first PN code; generating the second signals according the second PN code; transmitting the first signals to the first component; and transmitting the second signals to the second component. 
     In one embodiment, in order to transmit status of onboard sensor of the stylus, the method further comprises: generating data codes according to status of at least one onboard sensor; generating first data codes according to the data codes and the first PN code; transmitting the first data codes to the first component; transmitting, by the first component, the first data codes to the conductive tip section; and transmitting, by the conductive tip section, the first data codes. 
     In one embodiment, in order to transmit status of onboard sensor of the stylus, the method further comprises: generating data codes according to status of at least one onboard sensor; generating second data codes according to the data codes and the second PN code; transmitting the second data codes to the second component; transmitting, by the second component, the second data codes to the conductive tip section; and transmitting, by the conductive tip section, the first data codes. 
     In one embodiment, in order to synchronize with receiving procedure of a touch sensitive processing apparatus of a touch panel, the method is further configured for: receiving a synchronization signal from an electronic device; and after the synchronization signal is received, executing the generating steps and the transmitting steps. 
     In one embodiment, in order to synchronize with receiving procedure of the touch sensitive processing apparatus of the touch panel where the stylus touches or approximates, the synchronization signal which is being transmitted from electrodes of a touch panel of the electronic device to the conductive tip section. 
     In one embodiment, in order to prevent conflicts of PN codes when multiple styli operate with one touch panel, the method further comprises: receiving a setting instruction from a human-machine interface of the stylus for designating a set of the first PN code and the second PN code. 
     In one embodiment, in order to provide PN code setting information to user, the method further comprises at least one of following steps: having a visual indicator of the stylus indicating a set of the first PN code and the second PN code; and having an audio indicator of the stylus indicating the set of the first PN code and the second PN code. 
     In one embodiment, in order to provide a wire connection between the corded or tethered stylus and a touch sensitive processing apparatus, the method further comprises: receiving, by a first signal circuit, the first signals from a touch sensitive processing apparatus; propagating, by the first signal circuit, the first signals to the first component; receiving, by a second signal circuit, the second signals from the touch sensitive processing apparatus; and propagating, by the second signal circuit, the second signals to the second component. 
     In one embodiment, in order to provide a switch status to a touch sensitive processing apparatus, the method further comprises: selectively receiving, by a third component with fixed impedance, the first signals; and selectively transmitting, by the third component, the first signals to the conductive tip section. 
     In one embodiment, in order to provide a switch status to a touch sensitive processing apparatus, the method further comprises: selectively receiving, by a fourth component with fixed impedance, the second signals; and selectively transmitting, by the fourth component, the second signals to the conductive tip section. 
     One object of the present invention is to provide a touch sensitive processing apparatus for receiving electrical signals carrying pressure information transmitted from a first stylus, comprising: a sensing circuit, configured for receiving the electrical signals via electrodes of a touch panel; and a processor, coupled to the sensing circuit, configured for: despreading a first preamble code of the received electrical signals in accordance with a first pseudo-random number (PN) code; despreading a second preamble code of the received electrical signals in accordance with a second PN code; and calculating the pressure information according to a first signal strength ratio of a first part of the received electrical signal and a second part of the received electrical signal, wherein the first part comprises the first preamble code and the second part comprises the second preamble code, wherein the first PN code is orthogonal to the second PN code. 
     In one embodiment, in order to trigger the stylus for transmitting electrical signals synchronously, the touch sensitive processing apparatus further comprises a driving circuit, coupled to the electrodes of the touch panel, wherein the processor is further configured for having the driving circuit to transmit a beacon signal via the electrodes of the touch panel before the receiving step is being executed. 
     In one embodiment, in order to receive status of sensor onboard the stylus, the processor is further configured for: decoding first data codes of the received electrical signal in accordance with the first PN code, wherein the first data codes represents status of at least one onboard sensor of the first stylus. 
     In one embodiment, in order to receive status of sensor onboard the stylus, the processor is further configured for: decoding second data codes of the received electrical signal in accordance with the second PN code, wherein the second data codes represents status of at least one onboard sensor of the first stylus. 
     In one embodiment, in order to correctly receive status of sensor onboard the stylus, the processor is further configured for: decoding first data codes of the received electrical signal in accordance with the first PN code; decoding second data codes of the received electrical signal in accordance with the second PN code; and determining data codes if the first data codes and the second data codes are the same, wherein the data codes represents status of at least one onboard sensor of the first stylus. 
     In one embodiment, in order to receive more smooth and averaged pressure information in a longer transmission, the first part further comprises the first data codes and the second part further comprises the second data codes. 
     In one embodiment, in order to synchronize with the transmission of the stylus more quickly, the processor is further configured for: coupling at least two of second electrodes of the touch panel as a synchronization channel, wherein the despreading steps of the first preamble code and the second preamble code are being executed on the received electrical signals of the synchronization channel to retrieve a first synchronization information and a second synchronization information, respectively, wherein the second electrodes are arranged in parallel to each other. 
     In one embodiment, in order to correctly and quickly receive status of sensor onboard the stylus by utilizing synchronization information, the processor is further configured for: decoding first data codes of the received electrical signal from at least one of first electrodes of the touch panel in accordance with the first PN code and the first synchronization information; decoding second data codes of the received electrical signal from at least one of the first electrodes of the touch panel in accordance with the second PN code and the second synchronization information; and determining data codes if the first data codes and the second data codes are the same, wherein the data codes represents status of at least one onboard sensor of the first stylus, wherein the first electrodes are arranged in parallel to each other, and the first electrodes intersect with the second electrodes. 
     In one embodiment, in order to concurrently receive electrical signals from multiple styli, the processor is further configured for: despreading a third preamble code of the received electrical signals in accordance with a third PN code; despreading a fourth preamble code of the received electrical signals in accordance with a fourth PN code; and calculating a pressure information of a second stylus according to a second signal strength ratio of a third part of the received electrical signal and a fourth part of the received electrical signal, wherein the third part comprises the third preamble code and the fourth part comprises the fourth preamble code, wherein the first PN code, the second PN code, the third PN code and the fourth PN code are orthogonal to each other. 
     In one embodiment, in order to provide a wire connection between a corded or tethered stylus and the touch sensitive processing apparatus, the touch sensitive processing apparatus further comprises: a stylus interface, coupled to a first signal circuit and a second signal circuit of the first stylus, wherein the processor, coupled to the stylus interface, is further configured for: generating the first preamble code in accordance with the first PN code; generating the second preamble code in accordance with the second PN code; and transmitting the first preamble code and the second preamble code to the first signal circuit and the second signal circuit via the stylus interface, respectively. 
     In one embodiment, in order to receive status of a switch of the stylus, the processor is further configured for: calculating a switch status of the first stylus according to the first signal strength ratio of the first part of the received electrical signal and the second part of the received electrical signal. 
     In one embodiment, in order to concurrently connect with multiple corded or tethered styli, the stylus interface is further coupled to a third signal circuit and a fourth signal circuit of a second stylus. The processor, coupled to the stylus interface, is further configured for: generating a third preamble code in accordance with a third PN code; generating a fourth preamble code in accordance with a fourth PN code; and transmitting the third preamble code and the fourth preamble code to the third signal circuit and the fourth signal circuit via the stylus interface, respectively, wherein the first PN code, the second PN code, the third PN code and the fourth PN code are orthogonal to each other. 
     One object of the present invention is to provide a method for receiving electrical signals carrying pressure information transmitted from a first stylus, comprising: receiving the electrical signals via electrodes of a touch panel; despreading a first preamble code of the received electrical signals in accordance with a first PN code; despreading a second preamble code of the received electrical signals in accordance with a second PN code; and calculating the pressure information according to a first signal strength ratio of a first part of the received electrical signal and a second part of the received electrical signal, wherein the first part comprises the first preamble code and the second part comprises the second preamble code, wherein the first PN code is orthogonal to the second PN code. 
     In one embodiment, in order to trigger the stylus for transmitting electrical signals synchronously, the method further comprises: transmitting a beacon signal via the electrodes of the touch panel before the receiving step is being executed. 
     In one embodiment, in order to receive status of sensor onboard the stylus, the method further comprises: decoding first data codes of the received electrical signal in accordance with the first PN code, wherein the first data codes represents status of at least one onboard sensor of the first stylus. 
     In one embodiment, in order to receive status of sensor onboard the stylus, the method further comprises: decoding second data codes of the received electrical signal in accordance with the second PN code, wherein the second data codes represents status of at least one onboard sensor of the first stylus. 
     In one embodiment, in order to correctly receive status of sensor onboard the stylus, the method further comprises: decoding first data codes of the received electrical signal in accordance with the first PN code; decoding second data codes of the received electrical signal in accordance with the second PN code; and determining data codes if the first data codes and the second data codes are the same, wherein the data codes represents status of at least one onboard sensor of the first stylus. 
     In one embodiment, in order to receive more smooth and averaged pressure information in a longer transmission, the first part further comprises the first data codes and the second part further comprises the second data codes. 
     In one embodiment, in order to synchronize with the transmission of the stylus more quickly, the method further comprises: coupling at least two of second electrodes of the touch panel as a synchronization channel, wherein the despreading steps of the first preamble code and the second preamble code are being executed on the received electrical signals of the synchronization channel to retrieve a first synchronization information and a second synchronization information, respectively, wherein the second electrodes are arranged in parallel to each other. 
     In one embodiment, in order to correctly and quickly receive status of sensor onboard the stylus by utilizing synchronization information, the method further comprises: decoding first data codes of the received electrical signal from at least one of first electrodes of the touch panel in accordance with the first PN code and the first synchronization information; decoding second data codes of the received electrical signal from at least one of the first electrodes of the touch panel in accordance with the second PN code and the second synchronization information; and determining data codes if the first data codes and the second data codes are the same, wherein the data codes represents status of at least one onboard sensor of the first stylus, wherein the first electrodes are arranged in parallel to each other, and the first electrodes intersect with the second electrodes. 
     In one embodiment, in order to concurrently receive electrical signals from multiple styli, the method further comprises: despreading a third preamble code of the received electrical signals in accordance with a third PN code; despreading a fourth preamble code of the received electrical signals in accordance with a fourth PN code; and calculating a pressure information of a second stylus according to a second signal strength ratio of a third part of the received electrical signal and a fourth part of the received electrical signal, wherein the third part comprises the third preamble code and the fourth part comprises the fourth preamble code, wherein the first PN code, the second PN code, the third PN code and the fourth PN code are orthogonal to each other. 
     In one embodiment, in order to provide a wire connection between a corded or tethered stylus and the touch sensitive processing apparatus, the method further comprises: generating the first preamble code in accordance with the first PN code; generating the second preamble code in accordance with the second PN code; and transmitting the first preamble code and the second preamble code to a first signal circuit and a second signal circuit of the first stylus, respectively. 
     In one embodiment, in order to receive status of a switch of the stylus, the method further comprises: calculating a switch status of the first stylus according to the first signal strength ratio of the first part of the received electrical signal and the second part of the received electrical signal. 
     In one embodiment, in order to concurrently connect with multiple corded or tethered styli, the method further comprises: generating a third preamble code in accordance with a third PN code; generating a fourth preamble code in accordance with a fourth PN code; and transmitting the third preamble code and the fourth preamble code to a third signal circuit and a fourth signal circuit of a second stylus, respectively, wherein the first PN code, the second PN code, the third PN code and the fourth PN code are orthogonal to each other. 
     One object of the present invention is to provide a touch system, which comprising: a touch panel; a first stylus; and a touch sensitive processing apparatus for receiving electrical signals carrying pressure information transmitted from the first stylus. The touch sensitive processing apparatus comprises: a sensing circuit, configured for receiving the electrical signals via electrodes of the touch panel; and a processor, coupled to the sensing circuit, configured for: despreading a first preamble code of the received electrical signals in accordance with a first PN code; despreading a second preamble code of the received electrical signals in accordance with a second PN code; and calculating the pressure information according to a first signal strength ratio of a first part of the received electrical signal and a second part of the received electrical signal, wherein the first part comprises the first preamble code and the second part comprises the second preamble code, wherein the first PN code is orthogonal to the second PN code. 
     In one embodiment, the first stylus further comprises: a first component with variable impedance reflecting a pressure, wherein the first component is configured for receiving first signals encoded by the first PN code; a second component with fixed impedance, wherein the second component is configured for receiving second signals encoded by the second PN code; and a conductive tip section configured for: receiving, simultaneously, the first signals from the first component and the second signals from the second component; and transmitting the electrical signals which is composed of the first signals and the second signals. 
     One object of the present invention is to provide a stylus for transmitting electrical signals carrying pressure information, comprising: a first component with variable impedance reflecting a pressure, wherein the first component is configured for receiving first signals encoded by a pseudo-random number (PN) code in a first time period; a second component with fixed impedance, wherein the second component is configured for receiving second signals encoded by the PN code in a second time period; and a conductive tip section configured for: receiving the first signals from the first component in the first time period; receiving the second signals from the second component in the second time period; transmitting electrical signals which is composed of the first signals in the first time period; and transmitting electrical signals which is composed of the second signals in the second time period. 
     In one embodiment, in order to provide the PN code onboard the stylus, the stylus further comprises a controller, configured for: generating the first signals according to the PN code; generating the second signals according the PN code; transmitting the first signals to the first component; and transmitting the second signals to the second component. 
     In one embodiment, in order to transmit status of onboard sensor of the stylus, the stylus further comprises: at least one onboard sensor coupled to the controller, wherein the controller is further configured for: generating data codes according to status of the at least one onboard sensor; generating first data codes according to the data codes and the PN code; and transmitting the first data codes to the first component. The first component is further configured for receiving the first data codes from the controller in the first time period. The conductive tip section is further configured for in the first time period: receiving the first data codes from the first component; and transmitting the first data codes. 
     In one embodiment, in order to transmit status of onboard sensor of the stylus, the stylus further comprises: at least one onboard sensor coupled to the controller, wherein the controller is further configured for: generating data codes according to status of the at least one onboard sensor; generating second data codes according to the data codes and the PN code; and transmitting the second data codes to the second component. The second component is further configured for receiving the second data codes from the controller in the second time period. The conductive tip section is further configured for in the second time period: receiving the second data codes from the second component; and transmitting the second data codes. 
     In one embodiment, in order to synchronize with receiving procedure of a touch sensitive processing apparatus of a touch panel, the controller is further configured for: receiving a synchronization signal from an electronic device; and after the synchronization signal is received, executing the generating steps and the transmitting steps. 
     In one embodiment, in order to synchronize with receiving procedure of the touch sensitive processing apparatus of the touch panel where the stylus touches or approximates, the controller is coupled to the conductive tip section for receiving the synchronization signal which is being transmitted from electrodes of a touch panel of the electronic device. 
     In one embodiment, in order to prevent conflicts of PN codes when multiple styli operate with one touch panel, the stylus further comprises a human-machine interface for user&#39;s input of PN codes, wherein the controller is further configured for receiving a setting instruction from the human-machine interface for designating the PN code. 
     In one embodiment, in order to provide PN code setting information to user, the stylus further comprises at least one of following device coupled to the controller for indicating the PN code: a visual indicator; and an audio indicator. 
     In one embodiment, in order to provide a wire connection between the corded or tethered stylus and a touch sensitive processing apparatus, the stylus further comprises: a first signal circuit, coupled to the first component and a touch sensitive processing apparatus, configured for propagating the first signals from the touch sensitive processing apparatus to the first component; and a second signal circuit, coupled to the second component and the touch sensitive processing apparatus, configured for propagating the second signals from the touch sensitive processing apparatus to the second component. 
     In order to provide a switch status to a touch sensitive processing apparatus, the stylus further comprises: a third switch configured for receiving the first signals in the first time period; and a third component with fixed impedance, coupled to the third switch and the conductive tip section, wherein the third switch is selectively being opened or closed, the first signals are propagated through the third switch and the third component to the conductive tip section when the third switch is being closed. 
     In order to provide a switch status to a touch sensitive processing apparatus, the stylus further comprises: a fourth switch configured for receiving the second signals in the second time period; and a fourth component with fixed impedance, coupled to the fourth switch and the conductive tip section, wherein the fourth switch is selectively being opened or closed, the second signals are propagated through the fourth switch and the fourth component to the conductive tip section when the fourth switch is being closed. 
     One object of the present invention is to provide a method for transmitting electrical signals carrying pressure information from a stylus, comprising: receiving, by a first component with variable impedance reflecting a pressure, first signals encoded by a PN code in a first time period; receiving, by a second component with fixed impedance, second signals encoded by the PN code in a second time period; receiving the first signals from the first component by a conductive tip section in the first time period; receiving the second signals from the second component by the conductive tip section in the second time period; and transmitting electrical signals which is composed of the first signals in the first time period by the conductive tip section; and transmitting electrical signals which is composed of the second signals in the second time period by the conductive tip section. 
     In one embodiment, in order to provide the PN code onboard the stylus, the method further comprises: generating the first signals according to the PN code; generating the second signals according the PN code; transmitting the first signals to the first component; and transmitting the second signals to the second component. 
     In one embodiment, in order to transmit status of onboard sensor of the stylus, the method further comprises: generating data codes according to status of at least one onboard sensor; generating first data codes according to the data codes and the PN code; transmitting the first data codes to the first component; transmitting, by the first component, the first data codes to the conductive tip section; and transmitting, by the conductive tip section, the first data codes. 
     In one embodiment, in order to transmit status of onboard sensor of the stylus, the method further comprises: generating data codes according to status of at least one onboard sensor; generating second data codes according to the data codes and the PN code; and transmitting the second data codes to the second component; transmitting, by the second component, the second data codes to the conductive tip section; and transmitting, by the conductive tip section, the second data codes. 
     In one embodiment, in order to synchronize with receiving procedure of a touch sensitive processing apparatus of a touch panel, the method further comprises: receiving a synchronization signal from an electronic device; and after the synchronization signal is received, executing the generating steps and the transmitting steps. 
     In one embodiment, in order to synchronize with receiving procedure of the touch sensitive processing apparatus of the touch panel where the stylus touches or approximates, wherein the synchronization signal which is being transmitted from electrodes of a touch panel of the electronic device to the conductive tip section. 
     In one embodiment, in order to prevent conflicts of PN codes when multiple styli operate with one touch panel, the method further comprises: receiving a setting instruction from a human-machine interface of the stylus for designating the PN code. 
     In one embodiment, in order to provide PN code setting information to user, the method further comprises at least one of following steps: having a visual indicator of the stylus indicating the PN code; and having an audio indicator of the stylus indicating the PN code. 
     In one embodiment, in order to provide a wire connection between the corded or tethered stylus and a touch sensitive processing apparatus, the method further comprises: receiving, by a first signal circuit, the first signals from a touch sensitive processing apparatus; propagating, by the first signal circuit, the first signals to the first component; receiving, by a second signal circuit, the second signals from the touch sensitive processing apparatus; and propagating, by the second signal circuit, the second signals to the second component. 
     In one embodiment, in order to provide a switch status to a touch sensitive processing apparatus, the method further comprises: selectively receiving, by a third component with fixed impedance, the first signals; and selectively transmitting, by the third component, the first signals to the conductive tip section. 
     In one embodiment, in order to provide a switch status to a touch sensitive processing apparatus, the method further comprises: selectively receiving, by a fourth component with fixed impedance, the second signals; and selectively transmitting, by the fourth component, the second signals to the conductive tip section. 
     One object of the present invention is to provide a touch sensitive processing apparatus for receiving electrical signals carrying pressure information transmitted from a first stylus, comprising: a sensing circuit, configured for receiving the electrical signals via electrodes of a touch panel; and a processor, coupled to the sensing circuit, configured for: despreading a first preamble code of the received electrical signals in accordance with a pseudo-random number (PN) code in a first time period; despreading a second preamble code of the received electrical signals in accordance with the PN code in a second time period; and calculating the pressure information according to a first signal strength ratio of a first part of the received electrical signal and a second part of the received electrical signal, wherein the first part comprises the first preamble code and the second part comprises the second preamble code. 
     In one embodiment, in order to trigger the stylus for transmitting electrical signals synchronously, the touch sensitive apparatus further comprises: a driving circuit, coupled to the electrodes of the touch panel, wherein the processor is further configured for having the driving circuit to transmit a beacon signal via the electrodes of the touch panel before the receiving steps are being executed. 
     In one embodiment, in order to receive status of sensor onboard the stylus, the processor is further configured for: decoding first data codes of the electrical signal received in the first time period in accordance with the PN code, wherein the first data codes represents status of at least one onboard sensor of the first stylus. 
     In one embodiment, in order to receive status of sensor onboard the stylus, the processor is further configured for: decoding second data codes of the electrical signal received in the second time period in accordance with the PN code, wherein the second data codes represents status of at least one onboard sensor of the first stylus. 
     In one embodiment, in order to correctly receive status of sensor onboard the stylus, the processor is further configured for: decoding first data codes of the electrical signal received in the first time period in accordance with the PN code; decoding second data codes of the electrical signal received in the second time period in accordance with the PN code; and determining data codes if the first data codes and the second data codes are the same, wherein the data codes represents status of at least one onboard sensor of the first stylus. 
     In one embodiment, in order to receive more smooth and averaged pressure information in a longer transmission, the first part further comprises the first data codes and the second part further comprises the second data codes. 
     In one embodiment, in order to synchronize with the transmission of the stylus more quickly, the processor is further configured for: coupling at least two of second electrodes of the touch panel as a synchronization channel, wherein the despreading steps of the first preamble code and the second preamble code are being executed on the received electrical signals of the synchronization channel to retrieve a first synchronization information and a second synchronization information, respectively, wherein the second electrodes are arranged in parallel to each other. 
     In one embodiment, in order to correctly and quickly receive status of sensor onboard the stylus by utilizing synchronization information, the processor is further configured for: decoding first data codes of the received electrical signal from at least one of first electrodes of the touch panel in accordance with the PN code and the first synchronization information; decoding second data codes of the received electrical signal from at least one of the first electrodes of the touch panel in accordance with the PN code and the second synchronization information; and determining data codes if the first data codes and the second data codes are the same, wherein the data codes represents status of at least one onboard sensor of the first stylus, wherein the first electrodes are arranged in parallel to each other, and the first electrodes intersect with the second electrodes. 
     In one embodiment, in order to receive electrical signals from multiple styli, the processor is further configured for: despreading a third preamble code of the electrical signals received in a third time period in accordance with a second PN code; despreading a fourth preamble code of the electrical signals received in a fourth time period in accordance with the second PN code; and calculating a pressure information of a second stylus according to a second signal strength ratio of a third part of the received electrical signal and a fourth part of the received electrical signal, wherein the third part comprises the third preamble code and the fourth part comprises the fourth preamble code, wherein the PN code and the second PN code are orthogonal to each other, wherein part of the third time period is overlapped with part of the first time period or part of the second time period. 
     In one embodiment, in order to provide a wire connection between a corded or tethered stylus and the touch sensitive processing apparatus, the touch sensitive processing apparatus further comprises: a stylus interface, coupled to a first signal circuit and a second signal circuit of the first stylus, wherein the processor, coupled to the stylus interface, is further configured for: generating the first preamble code in accordance with the PN code; generating the second preamble code in accordance with the PN code; transmitting the first preamble code to the first signal circuit via the stylus interface in the first time period; and transmitting the second preamble code to the second signal circuit via the stylus interface in the second time period. 
     In one embodiment, in order to receive status of a switch of the stylus, the processor is further configured for: calculating a switch status of the first stylus according to the first signal strength ratio of the first part of the received electrical signal and the second part of the received electrical signal. 
     In one embodiment, in order to concurrently connect with multiple styli, the stylus interface is further coupled to a third signal circuit and a fourth signal circuit of a second stylus. The processor, coupled to the stylus interface, is further configured for: generating a third preamble code in accordance with a second PN code in a third time period; generating a fourth preamble code in accordance with the second PN code in a fourth time period; transmitting the third preamble code to the third signal circuit in the third time period via the stylus interface; and transmitting the fourth preamble code to the fourth signal circuit in the fourth time period via the stylus interface, respectively, wherein the PN code and the second PN code are orthogonal to each other, wherein part of the third time period is overlapped with part of the first time period or part of the second time period. 
     One object of the present invention is to provide a method for receiving electrical signals carrying pressure information transmitted from a first stylus, comprising: receiving the electrical signals via electrodes of a touch panel; despreading a first preamble code of the electrical signals received in a first time period in accordance with a PN code; despreading a second preamble code of the electrical signals received in a second time period in accordance with the PN code; and calculating the pressure information according to a first signal strength ratio of a first part of the received electrical signal and a second part of the received electrical signal, wherein the first part comprises the first preamble code and the second part comprises the second preamble code. 
     In one embodiment, in order to trigger the stylus for transmitting electrical signals synchronously, the method further comprises transmitting a beacon signal via the electrodes of the touch panel before the receiving step is being executed. 
     In one embodiment, in order to receive status of sensor onboard the stylus, the method further comprises: decoding first data codes of the electrical signal received in the first time period in accordance with the PN code, wherein the first data codes represents status of at least one onboard sensor of the first stylus. 
     In one embodiment, in order to receive status of sensor onboard the stylus, the method further comprises: decoding second data codes of the electrical signal received in the second time period in accordance with the PN code, wherein the second data codes represents status of at least one onboard sensor of the first stylus. 
     In one embodiment, in order to correctly receive status of sensor onboard the stylus, the method further comprises: decoding first data codes of the electrical signal received in the first time period in accordance with the PN code; decoding second data codes of the electrical signal received in the second time period in accordance with the PN code; and determining data codes if the first data codes and the second data codes are the same, wherein the data codes represents status of at least one onboard sensor of the first stylus. 
     In one embodiment, in order to receive more smooth and averaged pressure information in a longer transmission, the first part further comprises the first data codes and the second part further comprises the second data codes. 
     In one embodiment, in order to synchronize with the transmission of the stylus more quickly, the method further comprises: coupling at least two of second electrodes of the touch panel as a synchronization channel, wherein the despreading steps of the first preamble code and the second preamble code are being executed on the received electrical signals of the synchronization channel to retrieve a first synchronization information and a second synchronization information, respectively, wherein the second electrodes are arranged in parallel to each other. 
     In one embodiment, in order to correctly and quickly receive status of sensor onboard the stylus by utilizing synchronization information, the method further comprises: decoding first data codes of the received electrical signal from at least one of first electrodes of the touch panel in accordance with the PN code and the first synchronization information; decoding second data codes of the received electrical signal from at least one of the first electrodes of the touch panel in accordance with the PN code and the second synchronization information; and determining data codes if the first data codes and the second data codes are the same, wherein the data codes represents status of at least one onboard sensor of the first stylus, wherein the first electrodes are arranged in parallel to each other, and the first electrodes intersect with the second electrodes. 
     In one embodiment, in order to concurrently receive electrical signals from multiple styli, the method further comprises: despreading a third preamble code of the electrical signals received in a third time period in accordance with a second PN code; despreading a fourth preamble code of the electrical signals received in a fourth time period in accordance with the second PN code; and calculating a pressure information of a second stylus according to a second signal strength ratio of a third part of the received electrical signal and a fourth part of the received electrical signal, wherein the third part comprises the third preamble code and the fourth part comprises the fourth preamble code, wherein the PN code and the second PN code are orthogonal to each other, wherein part of the third time period is overlapped with part of the first time period or part of the second time period. 
     In one embodiment, in order to provide a wire connection between a corded or tethered stylus and the touch sensitive processing apparatus, the method further comprises: generating the first preamble code in accordance with the PN code in the first time period; generating the second preamble code in accordance with the PN code in the second time period; transmitting the first preamble code to a first signal circuit of the first stylus in the first time period; and transmitting the second preamble code to a second signal circuit of the first stylus in the second time period. 
     In one embodiment, in order to receive status of a switch of the stylus, the method further comprises: calculating a switch status of the first stylus according to the first signal strength ratio of the first part of the received electrical signal and the second part of the received electrical signal. 
     In one embodiment, in order to concurrently connect with multiple corded or tethered styli, the method further comprises: generating a third preamble code in accordance with a second PN code in a third time period; generating a fourth preamble code in accordance with the second PN code in a fourth time period; transmitting the third preamble code to a third signal circuit of a second stylus in the third time period; and transmitting the fourth preamble code to a fourth signal circuit of the second stylus in the fourth time period, wherein the PN code and the second PN code are orthogonal to each other, wherein part of the third time period is overlapped with part of the first time period or part of the second time period. 
     One object of the present invention is to provide a touch system comprising: a touch panel; a first stylus; and a touch sensitive processing apparatus. The touch sensitive processing apparatus for receiving electrical signals carrying pressure information transmitted from the first stylus, comprising: a sensing circuit, configured for receiving the electrical signals via electrodes of the touch panel; and a processor, coupled to the sensing circuit, configured for: despreading a first preamble code of the received electrical signals in accordance with a PN code in a first time period; despreading a second preamble code of the received electrical signals in accordance with the PN code in a second time period; and calculating the pressure information according to a first signal strength ratio of a first part of the received electrical signal and a second part of the received electrical signal, wherein the first part comprises the first preamble code and the second part comprises the second preamble code. 
     In one embodiment, the first stylus comprising: a first component with variable impedance reflecting a pressure, wherein the first component is configured for receiving first signals encoded by the PN code in the first time period; a second component with fixed impedance, wherein the second component is configured for receiving second signals encoded by the PN code in the second time period; and a conductive tip section configured for: receiving the first signals from the first component in the first time period; receiving the second signals from the second component in the second time period; transmitting electrical signals which is composed of the first signals in the first time period; and transmitting electrical signals which is composed of the second signals in the second time period. 
     The above embodiments are only used to illustrate the principles of the present invention, and they should not be construed as to limit the present invention in any way. The above embodiments can be modified by those with ordinary skill in the art without departing from the scope of the present invention as defined in the following appended claims.