Abstract:
A communication system for the wireless transmission of information through a single antenna is disclosed. The communication system comprises a handset and one or more modules capable of being coupled to the handset. The handset processes baseband information signals being received and transmitted, and transmits and receives radio frequency (RF) information signals through its antenna. Each module is removably couplable to the handset for converting baseband information signals into RF information signals for transmission, and for converting received RF information signals into baseband information signals. Each removably couplable module is optimized to enable wireless communication in accordance with at least one communication standard when coupled to the handset. By coupling the appropriate module with the handset, wireless communication in a number of geographic locations may be achieved.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates, generally, to communication systems and processes which use radio frequency (RF) transmitters and receivers (transceivers), and, in particular embodiments, to systems and processes for communication transceivers employing replaceable modules to minimize size, weight, complexity, power consumption, and cost. 
     2. Description of Related Art 
     It has become increasingly important to minimize the size, weight, complexity, power consumption, and cost of various electronic devices, especially personal communication devices such as cellular telephones, personal pagers, cordless telephones, and the like. One way to minimize such characteristics is to minimize the number of components and functions required in the electronic device, or to perform multiple functions using the same components. However, personal communication devices such as cellular telephones often utilize complex circuitry with a number of power-inefficient components for performing multiple functions. This is especially true in modern cellular communications, where several different communication standards are employed worldwide, and cellular telephones with the flexibility to operate under multiple communications standards are highly desirable from a consumer and manufacturing perspective. 
     For example, the Global System for Mobile (GSM) communication standard is a world-wide mode of digital cellular communication operating over three different frequency bands. GSM-900 operates in the 900 MHz frequency band and is currently used in Europe and Asia. DCS is another digital cellular standard based on GSM technology, operating in the 1800 MHz frequency band and also currently used in Europe and Asia. The United States uses PCS, a third digital cellular standard similar to DCS, but operating in the 1900 MHz band. GSM is currently used in approximately 154 countries, including the geographic areas of North Africa, India, China, Europe, the Middle East, and Taiwan. 
     However, GSM is not the only mode of cellular communication. CDMA is another mode of digital cellular communication operating in either the 900 or 1900 MHz band. CDMA is one of the most widely used modes of cellular communication in the United States, and is the most widely used mode of cellular communication in Korea. CDMA is also being used in China, India, and Taiwan. It should be noted that other communication standards also exist around the world. 
     With improved voice and data communications and political climates continuing to expand the world market, a “world telephone” capable of operating in many different countries is of interest to international business and recreational travelers. Multi-mode, multi-band cellular telephones with shared functionality and an optimized architecture capable of operating under all of these standards afford consumers widespread applicability and allow manufacturers to benefit from the cost-efficiency of a common design. 
     However, multi-mode, multi-band cellular telephones present a number of design challenges. Conventional single-band transmitters typically require two separate frequencies, a fixed intermediate frequency (IF) for modulation and a tunable RF for upconversion. Conventional single-band receivers also typically require two separate frequencies, a tunable RF for downconversion and a fixed IF for demodulation. Thus, a single-band cellular telephone may require as many as four different frequency sources. Multi-band and multi-mode cellular telephones exacerbate the problem because the modulation, upconversion, downconversion, and demodulation processes for each band and mode may operate at different frequencies and amplitudes. Furthermore, the frequencies and amplitudes employed by each band and mode may require different filters and amplifiers for the transmit and receive function of each band. The design challenge of producing cellular telephones of minimal size, weight, complexity, power consumption, and cost is thus compounded by multi-mode, multi-band cellular telephones. 
     A current trend in attempting to solve this design challenge is the concept of a “software radio,” which focuses on utilizing as much digital processing as possible. By utilizing digital technology, multi-mode, multi-band transceiver functions can be implemented more generically, with fewer analog components and fewer bulky filters. A problem with digital technology, however, is that a higher resolution ADC (Analog to Digital Converter) may be required. The digital components may be more inefficient than functionally comparable analog components, resulting in greater power consumption. Greater power consumption, in turn, may require a larger battery, negating any size and weight saving achieved by the use of digital technology. 
     SUMMARY OF THE DISCLOSURE 
     Therefore, it is an advantage of embodiments of the present invention to provide a system and process for supporting multiple wireless standards with a single circuit architecture to minimize size, weight, complexity, power consumption, and cost. 
     It is a further advantage of embodiments of the present invention to provide a system and process for supporting multiple wireless standards with a single circuit architecture capable of receiving a replaceable module optimized for one or more communication standards to minimize size and power consumption. 
     These and other objects are accomplished according to a communication system for the wireless transmission of information through a single antenna. The communication system comprises a handset and one or more modules capable of being coupled to the handset. The handset processes baseband information signals being received and transmitted, and transmits and receives RF information signals through its antenna. Each module is removably couplable to the handset for converting baseband information signals into RF information signals for transmission, and for converting received RF information signals into baseband information signals. Each removably couplable module is optimized to enable wireless communication in accordance with at least one communication standard when coupled to the handset. By coupling the appropriate module with the handset, wireless communication in a number of geographic locations may be achieved. 
    
    
     These and other objects, features, and advantages of embodiments of the invention will be apparent to those skilled in the art from the following detailed description of embodiments of the invention, when read with the drawings and appended claims. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is block diagram representation of a system environment according to an example embodiment of the present invention. 
     FIG. 2 is a more detailed block diagram representation of the modulator in the system of FIG.  1 . 
     FIG. 3 is a block diagram representation of a communication transceiver including a handset and replaceable module according to an embodiment of the present invention. 
     FIG. 4 is a block diagram representation of a communication transceiver including a handset and replaceable module according to an alternative embodiment of the present invention. 
     FIG. 5 is a block diagram representation of a handset according to an embodiment of the present invention. 
     FIG. 6 is a perspective view of a communication transceiver including a handset and replaceable module according to an alternative embodiment of the present invention. 
     FIG. 7 is a perspective view of a communication transceiver including a handset and a replaceable module incorporated into a battery pack according to an alternative embodiment of the present invention. 
     FIG. 8 is a perspective view of a handset with a cover removed to reveal replaceable modules according to an alternative embodiment of the present invention. 
     FIG. 9 is a perspective view of a communication transceiver including a handset and a replaceable module, the replaceable module including the antenna according to an alternative embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     In the following description of preferred embodiments, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the preferred embodiments of the present invention. 
     Cellular communication systems employ several different communication standards worldwide and utilize several different frequency bands. For example, the GSM communication standard operates over three different bands, 900 MHz, 1800 MHz, and 1900 MHz, while the CDMA communication standard operates over two different bands, 900 MHz and 1900 MHz. Cellular telephones with the flexibility to operate under multiple communications standards afford consumers widespread applicability. However, the number of different communication standards and frequency bands makes it impractical for a cellular telephone to incorporate all the electronics necessary to operate in all of these modes. 
     Embodiments of the present invention therefore relate to cellular communication transceivers employing a common handset capable of receiving a replaceable module containing circuitry optimized for one or more communication standards. By coupling only those electronics needed for a particular communication standard into the common handset, unnecessary or inefficient electronics are minimized or eliminated. 
     It should be noted, however, that transceivers according to embodiments of the present invention are not unique to cellular communications and may be employed in a variety of communications electronics, including wireless transmission systems as well as wired systems. Thus, embodiments of the invention described herein may involve various forms of communications systems. However, for purposes of simplifying the present disclosure, preferred embodiments of the present invention are described herein in relation to personal wireless communications systems, including, but not limited to digital mobile telephones, digital cordless telephones, digital pagers, combinations thereof, and the like. Such personal communications systems typically include one or more portable or remotely located receiver and/or transmitter units. 
     A generalized representation of a communication system  10  according to an embodiment of the present invention is shown in FIG. 1, wherein communication system  10  includes a transmitting unit  12  and a receiving unit  14 , coupled for communication over a communication channel  42 . Transmitting unit  12  includes a modulator  16  coupled to receive a digital transmit baseband information signal  18  from a baseband processor  58 . In one representative embodiment, the baseband processor  58  may include, for example, a microphone for converting sound waves into electronic signals and sampling and analog-to-digital converter electronics for sampling and converting the electronic signals into digital signals representative of the sound waves. In other embodiments, the signal source may include any suitable device for producing digital data signals for communication over channel  42 , such as, but not limited to, a keyboard, a digital voice encoder, a mouse or other user input device, a sensor, monitor or testing apparatus, or the like. 
     Modulator  16  provides a second transmit IF information signal  32  as an output to a transmitter  20 . A transmit RF information signal  26  is produced by transmitter  20  for transmission from an antenna  22 . Receiving unit  14  includes a receiver  24  coupled to antenna  22  to process a receive RF information signal  44 . Receiver  24  provides a modulated second receive IF information signal  34  to a demodulator  28 , which demodulates second receive IF information signal  34  and generates digital receive baseband information signals  46 . 
     Demodulated digital receive baseband information signals  46  from demodulator  28  are provided to baseband processor  58 , which may include signal processing electronics, sound producing electronics or the like, depending upon the nature of use of receiving unit  12 . Transmitting and receiving units  12  and  14  include further components, power supplies, and the like, well known in the art for effecting transmission and reception of signals and for carrying out other functions specific to the nature and application of use of communication system  10 . 
     In preferred communication system embodiments, such as cellular telephone embodiments or cordless telephone embodiments, a transceiver  48  includes both transmitting unit  12  and receiving unit  14  as shown in FIG.  1 . In one system embodiment, multiple transceivers  48  transmit and receive signals directly therebetween. In other system embodiments, transceivers  48  communicate through one or more additional transceiver stations  30  (such as repeaters, base or cell stations, or the like). 
     As illustrated in the modulator  16  of FIG. 2, in digital cellular telephone or cordless telephone system embodiments digital transmit baseband information signal  18  provides sampled voice (or sound) signals in the form of baseband I and Q channel signals to an encoder  36 . In one preferred cellular telephone embodiment, encoder  36  comprises a Phase Shift Key encoder, such as, but not limited to, a π/4-shift Quadrature Phase Shift Key mapper with differential encoder (π/4 DQPSK), and shaping filters  38  comprise pulse shaping filters for smoothing the encoder output signal. An example of a π/4 DQPSK and pulse shaping electronics is described in the article titled: “π/4-shift QPSK Digital Modulator LSIC for Personal Communication Terminals,” by Tetsu Sakata, Kazuhiko Seki, Shuji Kubota and Shuzo Kato, Proc. 5th IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, 1994 (incorporated herein by reference). Other embodiments may employ other suitable encoding schemes, including but not limited to Amplitude Shift Keying and Frequency Shift Keying schemes. 
     I and Q outputs of the encoder pass through shaping filters  38  and then to frequency conversion and modulation electronics  40 , the output of which comprises a second transmit IF information signal  32 . Second transmit IF information signal  32  is then fed to transmitter  20  as shown in FIG. 1, which provides the transmit RF information signal  26  to the antenna  22  for transmission. 
     A communication transceiver  48  according to a preferred embodiment of the present invention is illustrated in FIG.  3 . Transceiver  48  includes a handset  86  and a replaceable module  84 . Included in handset  86  are baseband processor  58  and antenna  22  as described above with reference to FIG. 1, although it should be noted that in alternative embodiments, antenna  22  may be located within replaceable module  84 . In the transmit path of replaceable module  84 , digital transmit baseband information signals  18  provides sampled voice (or sound) signals in the form of baseband I and Q channel signals to an encoder  36 . Encoder  36  converts digital transmit baseband information signals  18  to analog signals, which are then filtered by shaping filters  38  to produce analog transmit baseband information signals  178 . Frequency conversion and modulation electronics  40  modulate a transmit IF local oscillator (LO)  50  with analog transmit baseband information signals  178  to produce a second transmit IF information signal  32  at an IF carrier frequency. Transmit IF LO  50  is generated by an IF LO frequency generator  52  comprising an IF LO frequency source  54  phase-locked to reference source  110  within handset  86  by transmit IF LO loop electronics  56 . In preferred embodiments of the present invention, IF LO frequency source  54  is a voltage controlled oscillator (VCO). However, in alternative embodiments of the present invention, IF LO frequency source  54  may be any adjustable frequency source. 
     Second transmit IF information signal  32  is then amplified by a transmit IF variable gain amplifier (VGA)  60  within transmitter  20 . Transmit IF VGA  60  provides power control by adjusting its gain based on commands received from the base station. It should be noted that although power control is critical in CDMA, a variable gain amplifier is not required for GSM, and thus in alternative embodiments of the invention transmit IF VGA  60  need not have variable gain. 
     The output of transmit IF VGA  60  is filtered by transmit IF filter  62 , which filters out noise including noise generated by the transmit IF VGA  60  in the receive band to meet receive band noise floor requirements. Transmit IF filter  62  has a center frequency approximately equivalent to the IF carrier frequency and a bandwidth sufficient to pass the modulated and amplified transmit IF information signal with minimal distortion. The output of transmit IF filter  62  is first transmit IF information signal  180 , which is then mixed with a transmit RF LO  64  in transmit upconverter mixer  66 . In preferred embodiments, transmit upconverter mixer  66  generates the difference between the output of transmit IF filter  62  and transmit RF LO  64 . In alternative embodiments of the present invention, transmit upconverter mixer  66  may be replaced by a translation loop. 
     In embodiments of the present invention, transmit RF LO  64  is generated by a RF LO frequency generator  68  containing a RF LO frequency source  70  phase-locked to reference source  110  within handset  84  by RF LO loop electronics  72 . In preferred embodiments, RF LO frequency source  70  comprises a VCO. However, in alternative embodiments, RF LO frequency source  70  may be any adjustable frequency source. 
     The output of transmit upconverter mixer  66  is filtered by first transmit RF filter  74  which has a passband encompassing the transmit band of the particular communication standard of replaceable module  84  to remove spurious frequencies generated by transmit upconverter mixer  66 . The output of first transmit RF filter  74  is then amplified by transmit RF driver amplifier  76 , which amplifies the low level output of first transmit RF filter  74 . The output of transmit RF driver amplifier  76  is then filtered by second transmit RF filter  78 , which has a passband encompassing the transmit band of the particular communication standard of replaceable module  84  to filter out noise in the receive band including noise generated by transmit RF driver amplifier  76 . The output of second transmit RF filter  78  is then amplified by transmit RF power amplifier  80  to generate transmit RF information signal  26  at a level sufficient to meet output power requirements at antenna  22 . Transmit RF information signal  26  is then filtered by duplexer  82 , which has a transmit passband encompassing the transmit band of the particular communication standard of replaceable module  84  to filter out-of-band noise generated by transmit RF power amplifier  80 . The output of duplexer  82  is then transmitted by antenna  22 . In alternative embodiments of the present invention, duplexer  82  may be replaced by an RF switch or a resistor combiner. 
     In the receive path, signals from antenna  22  are filtered by duplexer  82  having a receive passband encompassing the receive band of the particular communication standard of replaceable module  84  for passing only receive band signals. The output of duplexer  82  is receive RF information signal  88 , which is amplified by a receive RF low noise amplifier (LNA)  90 . The output of receive RF LNA  90  is then filtered by a receive RF image reject filter  92 . Receive RF image reject filter  92  is a bandpass filter with a passband encompassing the receive band of the particular communication standard of replaceable module  84  to filter out image noise present at the output of the receive RF LNA  90  capable of mixing with receive RF LO  94  in receive downconverter mixer  96  and producing unwanted signals in the IF band. In preferred embodiments of the present invention, receive RF LO  94  is generated by RF LO frequency generator  68 , and receive downconverter mixer  96  generates the difference between the output of receive RF image reject filter  92  and receive RF LO  94 , designated herein as first receive IF information signal  102 . 
     First receive IF information signal  102  then passes through a receive IF filter  98  with a bandwidth encompassing the modulation bandwidth of the particular communication standard of replaceable module  84  to remove spurious frequencies generated by receive downconverter mixer  96 . The output of receive IF filter  98  is then fed into receive IF VGA  100 . Receive IF VGA  100  provides variable gain control by adjusting its gain based on commands received from the base station. The output of receive IF VGA  100  is second receive IF information signal  34 . 
     Second receive IF information signal  34  is mixed with receive IF LO  116  and demodulated by frequency conversion and demodulation electronics  104  within demodulator  28 . In embodiments of the present invention, receive IF LO  116  is generated by IF LO frequency generator  52 . 
     Frequency conversion and demodulation electronics  104  produce analog receive baseband information signals  120 , characterized herein as either DC or a “near DC” IF (for example, a center frequency of about 1 MHz). Analog receive baseband information signals  120  are filtered by baseband filters  106  to remove any spurious frequencies. Baseband filters  106  have a bandwidth sufficient to accommodate the modulation bandwidth of the particular communication standard of replaceable module  84 , and may be low pass filters if the receive baseband signals are DC, or bandpass filters if the receive baseband signals are near DC. The filtered and demodulated receive baseband signals are then processed by quantizers  108 , which generate digital receive baseband information signals  46 . In preferred embodiments, quantizers  108  are analog-to-digital converters (ADCs). 
     It should be noted that the replaceable module  84  of FIG. 3 is only illustrative of the functional blocks that might reside in the module. For example, in alternative embodiments of the present invention illustrated in FIG. 4, handset  86  may incorporate one or more of the following functional blocks: modulator  16 , demodulator  28 , IF LO frequency generator  52 , receive IF VGA  100 , receive IF filter  98 , transmit IF VGA  60 , and transmit IF filter  62 . In addition, although not shown in FIG. 5, antenna  22  may be included in replaceable module  84  instead of handset  86 . 
     FIG. 5 is a more detailed block diagram of handset  86  according to a preferred embodiment of the present invention. In addition to baseband processor  58 , reference source  110 , and antenna  22  as shown in FIG. 3, handset  86  further includes real-time clock (RTC)  112  for maintaining the time of day and date, battery charger power control  118 , keyboard backlight array  122 , keypad  124 , Universal Asynchronous Receiver/Transmitter (UART)  126 , system connector  128 , UART serial data services (SDS) interface  130 , IrDA Tx/Rx infrared transceiver  132 , Pulsed Width Modulator (PWM)  134 , annunciator  136 , vibrator electronics (VIB)  138 , and vibrator  140 , all well known in the art for effecting transmission and reception of signals and for carrying out other functions specific to the nature and application of use of transceiver  48 . Baseband processor  58  further includes a controller  142 , audio processor  144 , flash Read Only Memory (ROM)  146 , Random Access Memory (RAM)  148 , and programmable modulator/demodulator (modem) hardware  150 . 
     For each communication standard, software is required to properly perform baseband processing. In preferred embodiments of the present invention, the software for each communication standard is preprogrammed into ROM  146 . Through a serial control interface to replaceable module  84 , a separate portion of the software responsible for start-up processing polls replaceable module  84  upon power-up of transceiver  48 , and receives back a data string identifying the communication standard associated with that module. Based on that identifying data string, the proper software is then accessed in ROM  146  during the operation of transceiver  48 . 
     In alternative embodiments of the present invention, the software for each communication standard is preprogrammed into nonvolatile memory (not shown in FIG. 5) resident in module  84 . Through a serial control interface to replaceable module  84 , software responsible for start-up processing within ROM  146  initiates a serial transfer of the software in module  84  into RAM  148  upon power-up of transceiver  48 . The software within RAM  148  is then accessed during the operation of transceiver  48 . 
     In a further alternative embodiment of the present invention, the software for each communication standard is preprogrammed into nonvolatile memory (not shown in FIG. 5) resident in module  84 . Through a parallel data interface to replaceable module  84 , software within the nonvolatile memory is directly accessed during the operation of transceiver  48 . 
     In still further alternative embodiments of the present invention, the software for each communication standard is initially not located in either handset  86  or replaceable module  84 , but is downloaded into transceiver  48  from an external source. In one such embodiment, transceiver  48  is coupled to a digital device such as a personal computer via system connector  128  or through an infrared data interface, and a download sequence is initiated to transfer the appropriate software from the digital device to RAM  148  within handset  86 . The digital device may itself have received the appropriate software from a CD-ROM, magnetic media, the internet, or the like. 
     In another such alternative embodiment, a minimal amount of software is preprogrammed into nonvolatile memory in replaceable module  84 . This minimal set of software corresponds to the communication standard of the particular module  84 , and provides transceiver  48  with minimal capabilities sufficient to establish communications with the network at that standard. Once the communication link is established, the remainder of the software is downloaded from the network into RAM  148  to provide transceiver  48  with full functionality. 
     In preferred embodiments of the invention, a portion of RAM  148  is reserved for storing user-programmed phone numbers, games, and the like into handset  86 . With this capability, handset  86  can be configured for use with any number of communication standards simply by coupling in the appropriate module  84  while avoiding the need to reprogram this custom information. 
     In preferred embodiments of the invention illustrated in FIG. 6, replaceable module  84  is a plug-in unit with a housing  154  protecting sensitive circuitry within. Replaceable module  84  is shaped to be insertable into card slot  162  by the user. Along one or more edges of replaceable module  84  are contacts  156  for engagement with mating connectors (not shown in FIG. 6) within handset  86 . Also along one or more edges of replaceable module  84  are disengagement tabs  158  for removing replaceable module  84  from handset  86 . Housing  154  may contain one or more guide slots or ridges  160  for aligning replaceable module  84  into card slot  162 , and for ensuring that replaceable module  84  is inserted with the proper orientation. In further alternative embodiments of the present invention illustrated in FIG. 7, replaceable module  84  is located in the same housing  152  as a replaceable battery pack  164 . In another alternative embodiment illustrated in FIG. 9, antenna  22  is included as part of the replaceable module  84 . The replaceable module  84  of FIG. 9 may or may not include battery pack  164 . 
     While FIGS. 6,  7 , and  9  illustrate embodiments in which replaceable module  84  is user-replaceable without the need for removal of any part of the housing of handset  86 , in still further alternative embodiments illustrated in FIG. 8, module  84  is replaceable only by removing a cover  176  of handset  86 . In FIG. 8, replaceable module  84  may comprise a multi-chip module (MCM)  166  insertable into a zero-insertion force (ZIF) socket  168 , or a printed circuit board (PCB)  170  insertable into a spring-force connector  172 . 
     A number of business approaches may be employed by wireless communications providers to facilitate the use of transceiver  48 . For example, a user may be required to purchase replaceable modules  84  and bring the appropriate replaceable module to a particular region in order to establish a communication link. Knowledge of applicable communication standards in a particular region may be obtained from maps, or by calling a communications provider. If the particular communication standard in the region is unknown, a user must plug in one replaceable module at a time until the appropriate module is found. Alternatively, replaceable modules  84  can be rented from regional offices of the local communications provider. A user can then simply visit the regional office and rent the module appropriate for that area. 
     When using transceiver  48  in networks outside the user&#39;s home communication area, billing information must be routed back to the user&#39;s account with the home communications provider. In one example, a remote billing account is established in advance of visiting the remote location by contacting either the user&#39;s home communications provider, who will then establish an account with the remote communications provider, or by contacting the remote communications provider directly. In addition, transceivers may be electronically registered for use in remote areas in advance of visiting the remote location by downloading (from the home network) account numbers, personal identification numbers, and other electronic keys that will allow transceiver  48  to establish communications in the remote location. 
     Alternatively, a remote billing account is not established in advance of visiting the remote location. Instead, the user accesses the remote network with an unregistered phone and enters a credit card or account number for billing purposes. In further alternative embodiments illustrated in FIG. 6, a card reader  174  employed within handset  86  is used to read credit or account cards or bar-code information. 
     Therefore, according to the foregoing description, preferred embodiments of the present invention provide a system and process for supporting multiple wireless standards with a single circuit architecture. In preferred embodiments, the single circuit architecture is capable of receiving a replaceable module optimized for one or more communication standards to minimize size, weight, complexity, power consumption, and cost. 
     The foregoing description of preferred embodiments of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. It is intended that the scope of the invention be limited not by this detailed description, but rather by the claims appended hereto.