Patent Publication Number: US-9841862-B2

Title: Stylus position system

Description:
TECHNICAL FIELD 
     The present invention relates generally to the field of touch-sensing devices and more particularly to a stylus position system. 
     BACKGROUND 
     Conventional touch-sensing devices may detect the presence and location of a touch or the proximity of an object (such as a user&#39;s finger or a stylus) within a touch-sensitive area. A touch-sensing device may be, or may be associated with, a desktop computer, laptop computer, tablet computer, personal digital assistant (PDA), smartphone, satellite navigation device, portable media player, portable game console, kiosk computer, point-of-sale device, household appliance, or other suitable device. 
     Conventional touch-sensing devices may utilize different types of touch-sensitive technologies such as, for example, resistive touch-sensing devices, surface acoustic wave touch-sensing devices, and capacitive touch-sensing devices. In capacitive touch-sensing devices, when an object touches or is brought in proximity to an electrode array of a touch-sensing device, a change in capacitance may occur within the electrode array at the location of the touch or proximity. The touch-sensing device may then process the change in capacitance to determine the position of the object. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present disclosure and its features and advantages, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  illustrates an example touch-sensing system. 
         FIG. 2  illustrates an example stylus that may be used in a touch-sensing system. 
         FIG. 3  illustrates an example sender that may be used in a stylus. 
         FIG. 4  illustrates an example touch-sensing device that may be used in a touch-sensing system. 
         FIG. 5  illustrates an example electrode array that may be used in a touch-sensing device. 
         FIG. 6  illustrates an example measurement circuit that may be used in a touch-sensing device. 
         FIG. 7  illustrates an example stylus and electrode array that may be used in a touch-sensing system. 
         FIG. 8  illustrates relationships between an example stylus and electrode array that may be used in a touch-sensing system. 
     
    
    
     DESCRIPTION OF EXAMPLE EMBODIMENTS 
     According to one embodiment, a method includes generating, by a stylus, a composite signal. The composite signal includes a first signal having a first frequency, the first signal being used by a touch-sensing device to determine a position of the stylus relative to the touch-sensing device, and a second signal having a second frequency. The second signal includes information indicating a status of the stylus, and the second frequency is higher than the first frequency, though in other embodiments, the second frequency may be less than or equal to the first frequency. The information indicating the status of the stylus may include battery information, orientation information, sensory information (such as information indicating an amount of force exerted on the tip of the stylus, information indicating a status of a button of the stylus, etc.) information indicating input from a user of the stylus, and/or information indicating the distance between the tip of the stylus and the touch-sensing device. The stylus sends the composite signal to the touch-sensing device. Utilizing a composite signal in this manner may allow for the transmission of different types of status information, such as battery status, stylus orientation, the stylus&#39;s distance from the touch-sensing device, and the amount of force exerted on a portion of the stylus, over the same components that are used to detect the position of the stylus. This may reduce the need for additional transceiver hardware, allow for more efficient communication between the stylus and the touch-sensing device, make communication between the stylus and touch-sensing device less prone to noise, and/or increase the throughput of data transmission. Various embodiments may provide some, all, or none of these benefits. 
     According to another embodiment, a system includes a touch-sensing device and a stylus. The touch sensing device includes an electrode array and a controller configured to control the electrode array. The electrode array includes a plurality of electrode line pairs, and each electrode line pair includes a first electrode line configured to send a first signal and a second electrode line configured to send a second signal. The stylus includes a sensor configured to measure the first signal and the second signal, a signal processor configured to determine position information based at least on the first signal and second signal, and a transmitter configured to send a signal comprising the position information to the touch sensing device. In certain embodiments, the first and second signals may be differentiated by using quadrature phase-shifting, signal encoding, frequency modulation; amplitude modulation; phase modulation; or other suitable means for differentiating signals. This may allow the stylus to determine its own position, improve positional accuracy, and/or provide more efficient utilization of touch-sensing hardware. Various embodiments may provide some, all, or none of these benefits. Various embodiments may provide some, all, or none of these benefits. 
     In yet another embodiment, a method includes generating, by a touch-sensing device, a first signal comprising information identifying a first electrode line of an electrode array of the touch-sensing device, the first signal having a first strength. The first electrode line sends the first signal to a stylus, which receives the first signal, the first signal having a received strength. The stylus sends a second signal comprising information based on the received first signal, and the touch-sensing device receives the second the second signal. A position of the stylus is determined based at least in part on the information identifying the first electrode line and the received strength of the first signal. This signaling scheme may improve the ability of stylus and finger-sensing to coexist and may also reduce interference between finger-sensing and stylus-sensing that may occur when both utilize the same electrode array. 
       FIG. 1  illustrates an example touch-sensing system  20 . Touch-sensing system  20  includes stylus  200  and touch-sensing device  100 , which has touch-sensitive area  104 . Touch-sensing device  100  may be a tablet computer, smart phone, touchpad, or other device configured to detect the presence of stylus  200  on or near touch-sensitive area  104 . Touch-sensing device  100  may have a display (not shown) situated behind touch-sensitive area  104 . The display may be a liquid crystal display (LCD), an LED display, an LED-backlight LCD, or any other suitable display, and the display may be visible through an electrode array (not shown) or a cover panel (not shown). 
     Stylus  200  may be an active stylus configured to communicate with touch-sensing device  100 . Stylus  200  may interact or communicate with touch-sensing device  100  when brought in contact with or in proximity to touch-sensitive area  104 . In certain embodiments, interaction between stylus  200  and touch-sensing device  100  may be capacitive or inductive. For example, in some embodiments, when stylus  200  is brought in contact with or in proximity to touch-sensitive area  104 , signals generated by stylus  200  may influence capacitive electrodes of touch-sensing device  100 , or signals generated by touch-sensing device  100  may influence capacitive electrodes of stylus  200 . In other embodiments, a power source of stylus  200  may be inductively charged by touch-sensing device  100 , or a power source of touch-sensing device  100  may be charged by stylus  200 . Other embodiments may utilize any suitable method of interaction and/or communication between stylus  200  and touch-sensing device  100  in place of or in addition to capacitance and induction, such as mechanical forces, current, voltage, or electromagnetic fields. The capacitive coupling, inductive coupling, and other coupling mechanisms may be utilized for a variety of purposes, such as detecting a position of stylus  200  or a finger and communicating information between stylus  200  and touch-sensing device  100 . 
       FIG. 2  illustrates an example stylus  200  that may be used in touch-sensing system  20  from  FIG. 1 . Stylus  200  includes processor  210 , sender  220 , and receiver  260 . In other embodiments, stylus  200  may include processor  210  and sender  220 , but not receiver  260 . Processor  210  may control sender  220  and receiver  260 . Receiver  260  may be configured to detect a signal generated by touch-sensing device  100  (not shown). Sender  220  may be configured to generate a signal that is received by touch-sensitive device  100  and used to determine the position of stylus  200  and/or information indicating a status of stylus  200 . For example, sender  220  may generate a drive signal that is detected by touch-sensing device  100  and used to identify the position of stylus  200 . In some embodiments, the drive signal may be detected by a capacitive electrode array of touch-sensing device  100  as described above. 
     In some embodiments, sender  220  generates a composite signal containing both the drive signal, which may be used to determine the position of stylus  200 , as well as a data signal that contains information indicating a status of stylus  200 . The status of stylus  200  may include, but is not limited to, the orientation of the stylus, whether a portion of the stylus is within a threshold distance of a portion of touch-sensing device  100 , sensory information (such as an amount of force exerted on the tip of the stylus, a status of a button of the stylus, etc.) and/or the status of a battery. For example, stylus  200  may encode the drive signal with information indicating the amount of pressure on the tip of stylus  200 . The composite signal may also communicate the orientation of stylus  200 , which may be based on gyroscopic information, or the distance of stylus  200  from touch-sensitive area  104 , which may be used to determine whether stylus  200  is in a “hover mode” with its tip positioned within a threshold distance. In various embodiments, the composite signal may include some, all, or none of this information. 
     The composite signal may be detected by the same capacitive electrode array of touch-sensing device  100  that is utilized to determine the position of stylus  200 . Communicating this status information to touch-sensing device  100  via electrode array  110  may reduce the need for additional transceiver hardware, allow for more efficient communication between the stylus and the touch-sensing device, make communication between the stylus and touch-sensing device less prone to noise, and/or increase the throughput of data transmission. 
     Sender  220  may also send information to touch-sensing device  100  via a wireless transmitter. For example, in a some embodiments, sender  220  generates a radio frequency (RF) signal (or an electromagnetic signal with another frequency) with an antenna, the signal containing information indicating the position of the stylus and/or a status of the stylus. In various embodiments, stylus  220  may include a single sender  220  configured to perform one of the functions described above, a single sender  220  configured to perform multiple functions, or multiple senders  220 . 
       FIG. 3  illustrates an example sender  220  that may be used in stylus  200  from  FIG. 2 . The example sender  220  may use frequency division multiplexing to combine the drive signal and data signal into a composite signal. Sender  220  includes drive signal generator  230  and data signal generator  240 , which are connected to combiner  250 . Combiner  250  is connected to transmitter  254 . Other embodiments utilizing time division multiplexing (not shown) may not include combiner  250  and may interleave transmission of the drive signal and data signal by alternating between transmission of the drive signal and the data signal. 
     In some embodiments, drive signal generator  230  may generate a drive signal by utilizing a voltage driver. In some embodiments the voltage driver may generate voltages between 5 to 50 V, though this range is not required. In other embodiments, the voltage driver may generate voltages between 12 and 20 V. In a particular embodiment, the voltage driver may generate a voltage of approximately 16 V. Data signal generator  240  may generate a data signal by modulating a carrier signal with a modulation signal that contains information indicating a status of stylus  200 . For example, stylus  200  may encode the drive signal with information indicating its battery status and/or the amount of pressure on its tip. Stylus  200  may also encode information indicating its orientation, which may be based on gyroscopic information, and/or the distance of stylus  200  from touch-sensitive area  104 , which may be used to determine whether stylus  200  is in a hover mode. The drive signal and the data signal may serve as inputs to combiner  250 , which may combine the drive signal and the data signal into a composite signal using, for example, frequency division multiplexing. In alternative embodiments, the composite signal may be generated using time division multiplexing. 
     Combiner  250  may then send the composite signal to transmitter  254 , which may transmit the composite signal to touch-sensing device  100  (not shown). In some embodiments this transmission may utilize the capacitive or inductive touch-sensing elements of touch-sensing device  100  described above. For example, a drive signal, now encoded with status information, may be sensed by electrode array  110  (not shown) based on a change in capacitance caused by the drive signal. This received composite signal may then be processed by one or more receive channels of touch-sensing device  100  so that the same signal can be used to determine stylus position information (which can be determined by measuring the change in capacitance at a plurality of electrode lines of electrode array  110 ) and the status information (which can be determined by processing the composite signal as a function of the data signal frequency). Sending the composite signal in this manner may allow for the transmission of different types of status information (such as the amount of force exerted on a portion of the stylus, the orientation of the stylus, whether a portion of the stylus is within a threshold distance of a portion of touch-sensing device  100 , and/or the status of a battery) over the same components that are used to detect the position of the stylus, which may reduce the need for additional transceiver hardware in stylus  200  and touch-sensing device  100 . Furthermore, the composite signal can be processed simultaneously by two or more receive channels, which may improve data throughput. 
     The data signal may have a higher frequency than the drive signal. For example, in some embodiments, the drive signal may have a frequency between 30 and 300 Hz, though this frequency range is not required. In other embodiments, the drive signal may have a frequency between 50 and 200 Hz. In a particular embodiment, the drive signal may have a frequency of approximately 100 Hz. Furthermore, in some embodiments, the data signal may have a frequency between 300 Hz and 300 GHz, though this frequency range is not required. In other embodiments, the data signal may have a frequency between 1 KHz and 5 GHz. In a particular embodiment, the data signal may have a frequency of approximately 2.4 GHz. In some embodiments, the frequency of the data signal may be at least twice the frequency of the drive signal frequency. The higher frequency of the data signal may allow for transmission of larger quantities of data that may be used to communicate the status of stylus  200 . The higher frequency of the data signal may also allow for transmission of the data signal via the same electrode array used to determine stylus position without disrupting the normal operation of the touch sensor. 
       FIG. 4  illustrates an example touch-sensing device  100  that may be used in touch-sensing system  20  from  FIG. 1 . Touch-sensing device  100  includes electrode array  110 , measurement circuit  150 , controller  174 , processor  176 , receiver  180 , and memory  190 . As shown in  FIG. 4 , electrode array  110  is connected to measurement circuit  150  and controller  174 , which are both connected to processor  176 . Processor  176  may also be connected to receiver  180  and memory  190 . Receiver  180  may receive signals from a different medium or using different techniques from those involving electrode array  110 , described above. Some embodiments may have multiple receivers  180 , while others may not include receiver  180 . 
     Touch sensor  108  and controller  174  may detect the presence and location of a touch or the proximity of an object within a touch-sensitive area of touch sensor  108 . Herein, reference to a touch sensor may encompass both the touch sensor and its controller, where appropriate. Touch sensor  108  includes one or more touch-sensitive areas. In some embodiments, touch sensor  108  may include electrode array  110  (shown in  FIG. 6 ). Electrode array  110  may be a plurality of electrode lines, which may be drive and sense electrodes (or an array of electrodes of a single type), disposed on one or more substrates, which may be made of a dielectric material. Herein, an electrode line may refer to a single conductive wire, a series of electrodes position in a line, or any other suitable electronic structure or series of electronic structures defining a line shape or other pattern. Such electrode lines may operate to detect finger and/or stylus position by mutual capacitance, self capacitance, induction, or any other suitable method of position detection. Herein, reference to an electrode array may encompass both the electrodes of the touch sensor as well as the substrate(s) on which they are disposed. An electrode (whether a ground electrode, a guard electrode, a drive electrode, or a sense electrode) may be an area of conductive material forming a shape, such as for example a disc, square, rectangle, thin line, loop, other suitable shape, or suitable combination of these. In some embodiments, one or more cuts in one or more layers of conductive material may create the shape of an electrode, and the area of the shape may be bounded by those cuts. Furthermore, touch sensors, electrode arrays, and electrode lines may be referred to as generating and/or sending a signal. In such cases, while the signal itself may be produced as a result of physical changes in the touch sensor or components of the touch sensor, the generation of the signal may be driven by the electrode array itself, the controller, and/or other components of touch-sensing device  100 . 
     Measurement circuit  150  may include circuitry configured to process signals received by electrode array  110 . The output of measurement circuit  150  may then be passed to processor  176  for further analysis, and the resulting information may be stored in memory  190 . Memory  190  also stores instructions that may be operable to, when executed by processor  176 , direct the operation of controller  174  and perform other operations. Controller  174  may be configured to control the operation of electrode array  110 . For example, controller  174  may control the generation and/or sending of signals by electrode array  110 . In some embodiments, controller  174  may control the generation and/or sending of a composite signal including a data signal and a drive signal by electrode array  110 . Controller  174  may also control the detection of signals by electrode array  110  and/or measurement circuit  150 . 
     Measurement circuit  150  and controller  174  may each contain multiple electronic structures on one or more chips. In some embodiments, measurement circuit  150  and controller  174  may be included in a single chip or other structure. Various operations of measurement circuit  150  and controller  174  may be controlled by hardware or by software stored in memory  190  or another memory device of touch-sensing device  100 . 
       FIG. 5  illustrates an example electrode array  110  that may be used in touch-sensing device  100  from  FIG. 4 . Electrode array  100  includes electrode lines  120  and electrode lines  130 . Electrode lines  120  and  130  may be drive and/or sense lines. Controller  174  may control the operation of electrode lines  120  and  130  such that each electrode line may operate as a drive line at one time and as a signal line at another time. 
     As shown in  FIG. 5 , in some embodiments, electrode lines  120  and  130  form a grid pattern, and electrode lines  120  may be orthogonal to electrode lines  130 . In other embodiments, electrode lines  120  and  130  may have other orientations and layouts. For example, electrode lines  120  may be curved, zigzagged, randomized, or have different orientations from one another, as may electrode lines  130 . Furthermore, certain embodiments may include multiple electrode arrays disposed in multiple layers, or electrode lines  120  may be disposed in a first layer while electrode lines  130  are disposed in a second layer. 
       FIG. 6  illustrates an example measurement circuit  150  that may be used in touch-sensing device  100  from  FIG. 4 . Measurement circuit  150  may process the frequency division multiplexed composite signal generated by sender  220  from  FIG. 3 . As shown in  FIG. 6 , measurement circuit  150  includes electrode array connection  151 , which is connected to electrode array  110 . Electrode array connection  151  is connected to receive channel  152  and receive channel  153 . 
     Receive channel  152  may be used to process the composite signal to determine the position of stylus  200  or a user&#39;s finger. Receive channel  153  may be used to process the composite signal to determine the stylus&#39;s status information, which may include, for example, the amount of force exerted on a portion of the stylus, the orientation of the stylus, information indicating if a portion of the stylus is within a threshold distance of a portion of touch-sensing device  100 , and/or the status of a battery. The output of receive channels  152  and  153  may be connected to processor  176 . 
     Receive channels  152  and  153  may allow touch-sensing device  100  to simultaneously process a composite signal received by electrode array  110  (not shown) in order to determine position information and status information in parallel. Because the signal received by the electrode lines of electrode array  110  contains both the lower frequency drive signal and the higher frequency data signal, receive channel  152  can analyze the changes in capacitance caused by the drive signal and detected at the various electrode lines of electrode array  110  in order to determine the position of stylus  200 , while receive channel  153  can analyze the higher frequency information that may be encoded in the same signal to determine the status information of stylus  200 . Thus, in some embodiments, touch-sensing device  20  may be able to determine the position of stylus  20  by analyzing the composite signal as a function of the first frequency and determine the information indicating the status of stylus  20  by analyzing the composite signal as a function of the second frequency. 
     As shown in  FIG. 6 , receive channel  152  may include switch  154 , integrator  155 , ADC  160 , and signal processor  162 . Integrator  155  includes capacitor  156  and op-amplifier  158 . Switch  154  is connected to capacitor  156  and the inverting input of op-amplifier  158 , and the non-inverting input of op-amplifier  158  may be connected to ground  159 . The output of op-amplifier  158  is connected to capacitor  156  and to analog-to-digital converter (ADC)  160 , which is connected to signal processor  162 . Integrator  155  may be used to detect the drive signal component of the composite signal as received by electrode array  110 , generating at its output a voltage proportional to the capacitance of one or more electrode lines of electrode array  110 . By processing the signal received by each of the electrode lines of electrode array  110 , touching sensing device can determine the position of stylus  200  or a user&#39;s finger. For example, the change in capacitance is greater at intersections of electrode lines  120  and  130  that are closer to the tip of stylus  200  or a user&#39;s finger. By analyzing the change in capacitance of the various electrodes, touch-sensing device  100  can thus determine the position of stylus  200  or a finger. 
     As shown in  FIG. 6 , receive channel  153  may include low noise amplifier (LNA)  164 , mixer  168 , mixer input connection  166 , filter  170 , and signal processor  172 . Electrode array connection  151  is connected to LNA  164 . The output of LNA  164  is connected to mixer  168 , which is also connected to mixer input connection  166 . The output of mixer  168  is connected to filter  170 , which is connected to signal processor  172 . Receive channel  152  may be used to demodulate the data signal component of the composite signal and determine the information indicating the status of the stylus. The composite signal can be processed by receive channel  153  in parallel with the processing of receive channel  152 , which may allow for greater data throughput. In certain embodiments, decoding the data signal in a separate channel using demodulating techniques, rather than utilizing integrator  155  to decode the data signal, may make the system less prone to noise. 
       FIG. 7  illustrates an example stylus  200  and electrode array  110  that may be used in touch-sensing system  20  from  FIG. 1 . Electrode array  110  has electrode lines  120  and  130 . Electrode lines  120   a  and  120   b  form electrode line pair  122 , and electrode lines  130   a  and  130   b  form electrode line pair  132 . As shown in  FIG. 7 , Stylus  200  has a position  140  with respect to electrode array  110 . Position  140  has an X-position along dimension  142  between electrode lines  120   a  and  120   b  and a Y-position along dimension  144  between electrode lines  130   a  and  130   b . Signals sent by electrode line pairs  122  and  132 , as well as other electrode line pairs formed by other electrode lines  120  and  130 , may be detected by stylus  200  and used to determine position  140 . 
     In some embodiments, electrode lines  120   a  and  120   b  may generate and/or send quadrature signals. For example, electrode lines  120   a  and  120   b  may send a first signal and a second signal, respectively, each signal having the same strength and same frequency, but with the second signal having a quadrature phase shift relative to the first signal. Stylus  200  may measure the signals sent by electrode line pair  122 , detecting the strength of the first signal and the second signal. The relative strengths of these signals, as received by stylus  200 , may be used to determine the relative distance of stylus  20  from electrode lines  120   a  and  120   b  and thereby determine the position of stylus  200  along dimension  142 . This same process may be done in succession by all the electrode line pairs formed by electrode lines  120 . 
     Furthermore, this process may be repeated with electrode line pair  132  and all other electrode line pairs formed by electrode lines  130 . Just as the processing of quadrature signals sent by electrode line pair  122  was used to determine the position of stylus  200  along dimension  142 , processing quadrature signals sent by electrode line pair  132  may allow for the determination of the position of stylus  200  along dimension  144 . Thus, by repeating this process for all electrode line pairs formed by electrode lines  120  and  130 , position  140  of stylus  200  can be determined. In some embodiments, stylus  200  may have a near-field coupling mechanism so that only a limited set of signals from electrode line pairs will be received. 
     In certain embodiments, stylus  200  may be configured to process the quadrature signals sent by the electrode line pairs of electrode array  110  and determine its own position, which it may then communicate back to touch-sensing device  100 . In other embodiments, stylus  200  may be configured to detect the strengths of the received signals and communicate the strengths of the signals received from each electrode line back to touch-sensing device  100 , at which point touch-sensing device  100  may determine the position of stylus  200  based on this information. In both of these embodiments, stylus  200  may communicate this information back to touch-sensing device  100  by using a separate wireless transmitter to generate a signal that may be received by receiver  180  (not shown) of touch-sensing device  100 , or stylus  200  may communicate this information via electrode array  110 . Communicating the information back to touch-sensing device  100  via electrode array  110  may utilize the same or similar methods to those described above for generating a data signal or a composite signal that can be detected by electrode array  110  and processed by measurement circuit  150  (not shown). For example, upon sensing quadrature signals sent by an electrode line pair of electrode array  110 , stylus  200  may determine position and/or status information based on the received signal and then combine a drive signal and a data signal including the information into a composite signal (or by otherwise encoding the information on the drive signal) which would then be received by the touch-sensing device via electrode array  110 . 
     Furthermore, in some embodiments, techniques other than quadrature signaling by electrode line pairs may be utilized to allow stylus  200  to differentiate the signals received from electrode array  110 . For example, information distinguishing the electrode lines may be encoded onto the signals. Stylus  200  would then be able to decode the information, allowing it to determine which signal was received from which electrode line. Using this information in conjunction with the relative strength of the received signals and/or phase shift information may allow the touch-sensor to operate in a finger touch mode only, with respect to sensing capacitive or inductive changes in touch sensor  108 , since stylus position could be detected by stylus  200  itself based on signals generated by the touch sensor. In other words, finger position could be directly detected by touch sensor  108  while stylus position is directly detected by stylus  200  and then communicated back to touch-sensing device  100 . 
     In some embodiments, a first electrode line sends a first signal having a first frequency, and a second electrode line sends a second signal having a second frequency. The second signal may have a quadrature phase-shift relative to the first signal. Stylus  200  receives the first signal at a first strength and receives the second signal at a second strength. Stylus  200  sends a response signal to touch-sensing device  100 , the response signal based on the first signal and the second signal, and the position of stylus  200  is determined based on the first and the second signal. The position of the stylus may be determined based at least on a difference between the first signal strength and the second signal strength. Furthermore, a third electrode line may send a third signal having a third frequency, a fourth electrode line may send a fourth signal having a fourth frequency, and the first and second electrode lines may be oriented in a first direction while the third and fourth electrode lines are oriented in a second direction, the first direction being different from the second direction. The first direction and the second direction may be substantially perpendicular. In determining the position of stylus  200 , a position along a first axis may be determined based at least on the first signal and the second signal, and a position along the second axis may be determined based at least on the third signal and the fourth signal. In sending the response signal to touch-sensing device  100 , a transmitter of stylus  200  may send the response signal to a wireless receiver of the touch-sensing device, or the response signal may be received by electrode array  110 . The position of stylus  200  may be determined by stylus  200 , and the response signal may include information indicating the position of stylus  200 . The position of stylus  200  may also be determined by touch-sensing device  100 , and the response signal may include information indicating the first strength and the second strength. 
       FIG. 8  illustrates example stylus  200  and electrode array  110  that may be used in touch-sensing system  20  from  FIG. 1 . As shown in  FIG. 8 , Stylus  200  has a stylus position  140  with respect to electrode array  110 . Stylus position  140  is located distance  146  from X-Y position  148 , which is an orthogonal projection of stylus position  140  onto the plane of electrode array  110 . X-Y position  148  has an X-position along dimension  142  and a Y-position along dimension  144 . 
     As described above, electrode array  110  may be configured to generate and/or send signals that may be detected by stylus  200 . In some embodiments, the signals sent by electrode lines  120  and  130  may be encoded with information that allows stylus  200  to determine its position  140  relative to touch-sensing device  100 . Encoding techniques may include, but are not limited to, spread-spectrum techniques, closed-loop power control, and other suitable techniques for generating a data signal that is under the noise floor of capacitive, inductive, or other touch-sensing techniques described above. This may ensure that the information encoded in the signal sent by electrode array  110  does not interfere with any of the other touch-sensing operations that may be performed by touch-sensing device  100  or stylus  200 . 
     In some embodiments, electrode line  120   a  may send a signal including information identifying itself as the electrode line sending the signal. This signal may also include information identifying the strength at which the signal was generated. Stylus  200  may then receive the signal sent by electrode line  120   a  at a particular strength, the difference between the strength of the signal as generated and as received being proportional to the distance between electrode line  120   a  and stylus  200 . This process may be repeated by electrode lines  120   b ,  120   c , and other electrode lines  120  in electrode array  110 . Furthermore, the same process can be repeated with electrode lines  130   a ,  130   b , and other electrode lines  130  in electrode array  110 . Thus, each electrode line  120  and  130  may send a signal to stylus  200 , each signal including information identifying which electrode line sent the signal. 
     Furthermore, in some embodiments, the signal may also include information indicating the strength at which it was sent, while in other embodiments, touch-sensing device  100  may be configured to generate the signals at a known predetermined strength. The information identifying which electrode line sent which signal, in conjunction with the strength at which each of these signals was received by stylus  200 , may be used to calculate the position of stylus  200  along dimensions  142  and  144  and thus X-Y position  148 . This information may also be used to determine distance  146  and thus position  140  of stylus  200 . 
     In some embodiments, stylus  200  may be configured to process the signals sent by electrode lines  120  and  130  and determine its own position, which it may then communicate back to touch-sensing device  100 . In other embodiments, stylus  200  may be configured to communicate the information indicating which electrode line sent each signal and the strength of each signal, as detected by stylus  200 , back to touch-sensing device  100 . In such embodiments, touch-sensing device  100  may then determine position  140  of stylus  200  based on this information. In both of these embodiments, stylus  200  may communicate this information back to touch-sensing device  100  by using a separate wireless transmitter to generate a signal that may be received by receiver  180  (not shown) of touch-sensing device  100 , or stylus  200  may communicate this information via electrode array  110 . Communicating the information back to touch-sensing device  100  via electrode array  110  may utilize the same or similar methods to those described above for generating a data signal or composite signal that can be detected by electrode array  110  and processed by measurement circuit  150  (not shown). For example, in some embodiments, stylus  200  may receive signals sent by electrode lines  120  and  130 , the signals encoded with information identifying which electrode line sent which signal. Stylus  200  may then send a response signal to touch-sensing device  100  via electrode array  110  based on the strength at which each signal was received and the encoded information. 
     In some embodiments, a first electrode line of an electrode array sends a first signal including information identifying the first electrode line, the first signal having a first strength. The first electrode line sends the first signal to stylus  200 . Touch-sensing device  100  then receives a received signal from stylus  200 , the received signal based at least in part on the information identifying the first electrode line and a strength at which the first signal was received by the stylus. The position of stylus  200  is then determined based at least in part on the information identifying the first electrode line and the strength at which the first signal was received by the stylus. The received signal may include information indicating the strength at which the first signal was received by stylus  200  and information identifying the first electrode line. The received signal may include information indicating the position of the stylus. The first signal may also include information indicating the strength at which the first signal was sent by the first electrode line, and the determination of the position of stylus  200  may be based further on the difference between the strength at which the first signal was sent by the first electrode and the strength at which the first signal was received by the stylus. The position of stylus  200  may include a position along a first, second, and third axes, wherein the first axis is different from the second axis, the first and second axes are substantially parallel to the electrode array, and the third axis is substantially perpendicular to the electrode array. 
     Furthermore, a second electrode line of the electrode array may send a second signal including information identifying the second electrode line, and determining the position of stylus  200  may be based further on the information identifying the second electrode line and a strength at which the second signal was received by stylus  200 . A third electrode line of the electrode array may send a third signal including information identifying the third electrode line, and a fourth electrode line of the electrode array may send a fourth signal including information identifying the fourth electrode line. The first and second electrode lines may be oriented in a substantially similar first direction, and the third and fourth electrode lines may be oriented in a substantially similar second, the first direction being different from the second direction. The first direction and the second direction may be substantially perpendicular. 
     In other embodiments, stylus  200  receives a first signal including information identifying a first electrode line of an electrode array of touch-sensing device  100 , the first signal have a first received strength. Stylus  200  analyzes the first signal to determine the first received strength and the information identifying the first electrode line. Stylus  200  then generates a first response signal based at least in part on the first received strength and the information identifying the first electrode line and sends the first response signal to touch-sensing device  100 . Stylus  200  may receive a second signal comprising information identifying a second electrode line of the electrode array, the second signal having a second received strength. The first response signal may be based further on the second received strength and the information identifying the second electrode line, or stylus  200  may generate a second response signal based at least in part on the second received strength and the information identifying the second electrode line. The first signal may further include information indicating a strength at which the first signal was sent by the first electrode line. The first response signal may include the position of stylus  200 , and stylus  200  may determine its position based at least in part on the first received strength, the information identifying the first electrode line, the second received strength, and the information identifying the second electrode line 
     Encoded signals generated by touch sensor  108  and received by stylus  200  with information used to determine the position of stylus  200  may improve the ability of touch sensor  108  to operate without interference. Using methods such as spread spectrum schemes or closed-loop power control may allow stylus  200  to receive signals that remain below the noise floor of touch sensor  108 . The reduced interference of this “water-marking” signaling scheme may improve the ability of finger-sensing and touch-sensing signaling to operate simultaneously. Furthermore, since finger-sensing and stylus-sensing schemes may require different signaling levels and time budgets for electrode touch sensor  108 , detecting finger position and stylus position via different pathways may improve performance of touch-sensing system  20  by obviating the need to accommodate their conflicting requirements in the same receive channel. Since design compromises caused by conflicting timing and signaling requirements of finger-sensing and stylus-sensing may be avoided, these methods may allow for improved performance of both finger-sensing and stylus-sensing. 
     Herein, “or” is inclusive and not exclusive, unless expressly indicated otherwise or indicated otherwise or indicated otherwise by context. Therefore, herein, “A or B” means “A, B, or both,” unless expressly indicated otherwise or indicated otherwise by context. Moreover, “and” is both joint and several, unless expressly indicated otherwise or indicated otherwise by context. Therefore, “A and B” means “A and B, jointly or severally,” unless expressly indicated otherwise or indicated otherwise by context. 
     This disclosure encompasses all changes, substitutions, variations, alterations, and modifications to the example embodiments herein that a person having ordinary skill in the art would comprehend. Similarly, where appropriate, the appended claims encompass all changes, substitutions, variations, alterations, and modifications to the example embodiments herein that a person having ordinary skill in the art would comprehend. Moreover, reference in the appended claims to an apparatus or system or a component of an apparatus or system being adapted to, arranged to, capable of, configured to, enabled to, operable to, or operative to perform a particular function encompasses that apparatus, system, component, whether or not it or that particular function is activated, turned on, or unlocked, as long as that apparatus, system, or component is so adapted, arranged, capable, configured, enabled, operable, or operative. 
     Various embodiments disclosed herein may be used together in a variety of combinations. In some embodiments, touch-sensing system  20  may use different types of touch-sensing device  100  and stylus  200 , and touch-sensing device  100  and stylus  200  may have different numbers and types of components, as well as different configuration and organization of those components. For example, in certain embodiments, stylus  200  may have different numbers and types of processor  210 , sender  220 , and receiver  260 , as well as additional components. As another example, in various embodiments, electrode array  110  may have different types, numbers, and orientations of electrodes lines  120  and  130 . For example, in some embodiments, electrode lines  120  and  130  may form a grid of perpendicular lines, while in other embodiments, electrode lines  120  and  130  may different sizes, shapes, and orientations. 
     Furthermore, in various embodiments, touch-sensing system  20  may utilize one or more of the communication methods described above to communicate information between touch-sensing device  100  and stylus  200  and vice versa. For example, in some embodiments, stylus  200  may receive a signal from touch-sensing device  100  that includes encoded information while also sending a combined signal including a drive signal and a data signal to touch-sensing device  100  via electrode array  110 . In other embodiments, stylus  200  may receive quadrature signals from electrode line pairs  122  and  132  while also sending a combined signal including a drive signal and a data signal to touch-sensing device  100  via electrode array  110 . In still other embodiments, stylus  200  may receive quadrature signals from electrode line pairs  122  and  132 , each quadrature signal encoded with information that may be used by stylus  200  to determine position and/or other information. 
     Although the present invention has been described above in connection with several embodiments; changes, substitutions, variations, alterations, transformations, and modifications may be suggested to one skilled in the art, and it is intended that the present invention encompass such changes, substitutions, variations, alterations, transformations, and modifications as fall within the spirit and scope of the appended claims.