Abstract:
A software defined transmit architecture includes a plurality of individually selectable components that can be selectively enabled to transmit a data signal that complies with any of a plurality of transmission standards. The software defined transmit architecture comprises components that can be enabled by associated logic to transmit, for example, communications signals that comply with the global system for mobile communications (GSM), enhanced data rates for GSM evolution (EDGE), which employs TDMA, and wide band code division multiple access (WCDMA) transmission standards. A single transmit architecture supports multiple transmission standards, thus minimizing the number of components in a multi-band, multi-mode portable transceiver, while reducing the number of active components.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates generally to transmit circuit architecture in a wireless portable communication device. More particularly, the invention relates to a software defined multiple transmit architecture for a wireless transmitter that is capable of communicating using multiple transmit methodologies. 
   2. Related Art 
   With the increasing availability of efficient, low cost electronic modules, mobile communication systems are becoming more and more widespread. For example, there are many variations of communication schemes in which various frequencies, transmission schemes, modulation techniques and communication protocols are used to provide two-way voice and data communications in a handheld, telephone-like communication handset. The different modulation and transmission schemes each have advantages and disadvantages. 
   As these mobile communication systems have been developed and deployed, many different standards, to which these systems must conform, have evolved. For example, in the United States, third generation portable communications systems comply with the IS-136 standard, which requires the use of a particular modulation scheme and access format. In the case of IS-136, the modulation scheme can be 8-quadrature phase shift keying (8QPSK), offset π/4 differential quadrature phase shift keying (π/4-DQPSK) or variations thereof and the access format is TDMA. 
   In Europe, the global system for mobile communications (GSM) standard requires the use of the gaussian minimum shift keying (GMSK) modulation scheme in a narrow band TDMA access environment, which uses a constant envelope modulation methodology. 
   Furthermore, in a typical GSM mobile communication system using narrow band TDMA technology, a GMSK modulation scheme supplies a very low noise phase modulated (PM) transmit signal to a non-linear power amplifier directly from an oscillator. In such an arrangement, a non-linear power amplifier, which is highly efficient, can be used thus allowing efficient modulation of the phase-modulated signal and minimizing power consumption. Because the modulated signal is supplied directly from an oscillator, the need for filtering, either before or after the power amplifier, is minimized. Further, the output in a GSM transceiver is a constant envelope (i.e., a non time-varying signal containing only a phase modulated (PM) signal) modulation signal. 
   Many non-constant envelope transmit architectures use a modulation scheme where both a PM signal and an amplitude modulated (AM) signal are transmitted. Standards employing these schemes increase the data rate without increasing the bandwidth of the transmitted signal. Unfortunately, even though it would be desirable to have one portable transceiver that can accommodate all of the above-mentioned transmission schemes, existing GSM modulation schemes are not easily adapted to transmit a signal that includes both a PM component and an AM component. One reason for this difficulty is that in order to transmit a distortion free signal containing a PM component and an AM component, a highly linear power amplifier is required. Unfortunately, highly linear power amplifiers are very inefficient, thus consuming significantly more power than a non-linear power amplifier and drastically reducing the life of the battery or other power source. 
   In non-constant envelope modulation, an amplitude modulated (AM) portion of the signal causes the transmit output signal to vary in amplitude. In constant envelope modulation, the transmit output signal is always at a constant amplitude. Emerging communication standards, such as enhanced data rates for GSM evolution (EDGE), which is an extension to the global system for mobile, communications (GSM) and wide band code division multiple access (WCDMA) will likely use a non-constant envelope modulation scheme. As the transmit architectures for these new standards are under development, it is generally desirable to have a single transmit architecture that supports as many standards as possible. 
   One possible manner of developing a single transmit architecture that is capable of both constant envelope and non-constant envelope modulation use a conventional upconverter with filters inserted into the transmit chain. Such an architecture requires filters at the intermediate frequency (IF), at the radio frequency (RF) before the power amplifier and at RF after the power amplifier. Unfortunately, a multi-standard transmit architecture would require many filters to be switched in and out of the transmit circuit, or would require separate transmit chains. 
   Further, when a new wireless communication system standard emerges, it is desirable to have a transmit architecture that can satisfy the new standard and still remain “backwards compatible” with existing standards. Often the new standard is designed using principles and techniques that are fundamentally at odds with one another. For example, an existing standard may us TDMA, narrow signal bandwidth, constant-envelope modulation (i.e., GSM), while a new standard may use code access (CDMA), wide signal bandwidth, non-constant envelope modulation (i.e., wideband CDMA (WCDMA)). Further, the two systems may operate in different frequency bands. Such differences in transmission standards cause a “ripple effect” throughout the system design process and will typically result in very different transmit architectures (i.e., different filtering, different power amplification, etc.). Yet, it is desirable to have a single transmit architecture that can satisfy multiple standards. 
   Existing transmit architectures for wireless digital standards are not sufficiently flexible to support alternative standards without significant modifications of the transmit hardware. As a result, existing multiple standard (also referred to as “multi-band” or “multi-mode”) transmit architectures require a significant number of components including both active and passive devices. This can require that a single portable communication device include two separate transmitters, resulting in a costly and excessively bulky device. Further, when operating in communication standards that require non-constant envelope modulation (i.e., standards that include an AM component), power efficiency is reduced, resulting in shortened battery life and increased heat dissipation from the active components. An example of such a situation is the universal mobile telephone service (UMTS) standard, which requires a portable communication device to operate in both GSM mode and WCDMA mode. 
   With the increasing desirability of developing one worldwide portable communication standard, it would be desirable to have a portable transceiver that can operate in multiple digital standards, while minimizing the number of components in the transmit architecture. 
   SUMMARY 
   Embodiments of the invention include a software defined multiple transmit architecture that is capable of operating using multiple transmit standards. A software defined transmit architecture includes a plurality of individually selectable components that can be selectively enabled to transmit a data signal that complies with any of a plurality of transmission standards. The software defined transmit architecture comprises components that can be enabled by associated logic to transmit, for example, communications signals that comply with the global system for mobile communications (GSM), enhanced data rates for GSM evolution (EDGE), which employs TDMA, and wide band code division multiple access (WCDMA) transmission standards. A single transmit architecture supports multiple transmission standards, thus minimizing the number of components in a multi-band, multi-mode portable transceiver, while reducing the number of active components. 
   Related methods of operation and computer readable media are also provided. Other systems, methods, features, and advantages of the invention will be or become apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features, and advantages be included within this description, be within the scope of the invention, and be protected by the accompanying claims. 

   
     BRIEF DESCRIPTION OF THE FIGURES 
     The invention can be better understood with reference to the following figures. The components within the figures are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the invention. Moreover, in the figures, like reference numerals designate corresponding parts throughout the different views. 
       FIG. 1  is a block diagram illustrating a simplified portable transceiver including a software defined transmit architecture. 
       FIG. 2  is a block diagram illustrating the software defined transmit architecture of  FIG. 1 . 
       FIG. 3  is a block diagram illustrating the components used when the software defined transmit architecture is operating using the GSM standard. 
       FIG. 4  is a block diagram illustrating the components used when the software defined transmit architecture is operating using the EDGE/TDMA standard. 
       FIG. 5  is a block diagram illustrating the components used when the software defined transmit architecture is operating using the WCDMA standard. 
       FIG. 6  is a flow chart describing the operation of the transmit definition software of  FIG. 1 . 
   

   DETAILED DESCRIPTION 
   Although described with particular reference to a portable transceiver, the software defined multiple transmit architecture can be implemented in any communication device in which multiple standard operation is desired. Furthermore, the software defined multiple transmit architecture is applicable to any transmitter in which constant-envelope and non-constant envelope modulation is used. 
   The software defined multiple transmit architecture can be implemented using a combination of software and hardware. The hardware portion of the invention can be implemented using specialized hardware elements and logic. The software portion can be stored in a memory and be executed by a suitable instruction execution system (microprocessor). The hardware implementation of the software defined multiple transmit architecture can include any or a combination of the following technologies, which are all well known in the art: a discrete logic circuit(s) having logic gates for implementing logic functions upon data signals, an application specific integrated circuit having appropriate logic gates, a programmable gate array(s) (PGA), a field programmable gate array (FPGA), etc. 
   The software for the software defined multiple transmit architecture comprises an ordered listing of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. 
   In the context of this document, a “computer-readable medium” can be any means that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. The computer readable medium can be, for example but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, device, or propagation medium. More specific examples (a non-exhaustive list) of the computer-readable medium would include the following: an electrical connection (electronic) having one or more wires, a portable computer diskette (magnetic), a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory) (magnetic), an optical fiber (optical), and a portable compact disc read-only memory (CDROM) (optical). Note that the computer-readable medium could even be paper or another suitable medium upon which the program is printed, as the program can be electronically captured, via for instance optical scanning of the paper or other medium, then compiled, interpreted or otherwise processed in a suitable manner if necessary, and then stored in a computer memory. 
     FIG. 1  is a block diagram illustrating a simplified portable transceiver  100  including a software defined transmit architecture. Portable transceiver  100  includes speaker  102 , display  104 , keyboard  106 , and microphone  108 , all connected to baseband subsystem  110 . In a particular embodiment, portable transceiver  100  can be, for example but not limited to, a portable telecommunication handset such as a mobile cellular-type telephone. Speaker  102  and display  104  receive signals from baseband subsystem  110  via connections  112  and  114 , respectively, as known to those skilled in the art. Similarly, keyboard  106  and microphone  108  supply signals to baseband subsystem  110  via connections  116  and  118 , respectively. Baseband subsystem  110  includes microprocessor (μP)  120 , memory  122 , analog circuitry  124 , and digital signal processor (DSP)  126  in communication via bus  128 . Bus  128 , although shown as a single bus, may be implemented using multiple busses connected as necessary among the subsystems within baseband subsystem  110 . 
   Depending on the manner in which the software defined multiple transmit architecture to be described below is implemented, the baseband subsystem  110  may also include an application specific integrated circuit (ASIC)  135  and a field programmable gate array (FPGA)  133 . 
   Microprocessor  120  and memory  122  provide the signal timing, processing and storage functions for portable transceiver  100 . Analog circuitry  124  provides the analog processing functions for the signals within baseband subsystem  110 . Baseband subsystem  110  provides control signals to radio frequency (RF) subsystem  130  via connection  132 . Although shown as a single connection  132 , the control signals may originate from the DSP  126 , the ASIC  135 , the FPGA  133 , or from microprocessor  120 , and are supplied to a variety of points within RF subsystem  130 . It should be noted that, for simplicity, only the basic components of portable transceiver  100  are illustrated herein. The control signals provided by the baseband subsystem  110  control the various components within the RF subsystem  130 , as will be described in detail below. 
   If the software defined multiple transmit architecture is implemented in software that is executed by the microprocessor  120 , the memory  122  will also include the transmit definition software  300 , which will be described in detail below. The transmit definition software comprises one or more executable code segments that can be stored in the memory and executed in the microprocessor  120 . Alternatively, the functionality of the transmit definition software  300  can be coded into the ASIC or can be executed by the FPGA. Because the memory  122  can be rewritable and because the FPGA is reprogrammable, updates to the transmit definition software  300  can be remotely sent to and saved in the portable transceiver  100  when implemented using either of these methodologies. 
   Baseband subsystem  110  also includes analog-to-digital converter (ADC)  134  and digital-to-analog converters (DACs)  136  and  138 . Although DACs  136  and  138  are illustrated as two separate devices, it is understood that a single digital-to-analog converter may be used that performs the function of DACs  136  and  138 . ADC  134 , DAC  136  and DAC  138  also communicate with microprocessor  120 , memory  122 , analog circuitry  124  and DSP  126  via bus  128 . DAC  136  converts the digital communication information within baseband subsystem  110  into an analog signal for transmission to RF subsystem  130  via connection  140 . DAC  138  provides a reference voltage power level signal to power control element  161  via connection  144 . Connection  140 , while shown as two directed arrows, includes the information that is to be transmitted by RF subsystem  130  after conversion from the digital domain to the analog domain. 
   RF subsystem  130  includes modulator  146 , which, after receiving a frequency reference signal, also called a “local oscillator” signal, or “LO,” from synthesizer  148  via connection  150 , modulates the received analog information and provides a modulated signal via connection  152  to upconverter  154 . In a constant envelope modulation methodology, the modulated transmit signal generally includes only phase information. Upconverter  154  also receives a frequency reference signal from synthesizer  148  via connection  156 . Synthesizer  148  determines the appropriate frequency to which the upconverter  154  upconverts the modulated signal on connection  152 . 
   As will be described in detail below, the synthesizer  148 , the modulator  146 , the upconverter  154 , and the power amplifier  160 , along with other components to be described below, form the software defined multiple transmit architecture that is capable of transmitting information that complies with any of a plurality of communication standards. The software defined transmit architecture  200  generally comprises a plurality of selectable components. The selectable components together comprise a plurality of different transmit architectures in which a number of components are shared among the different transmit architectures. The transmit definition software  300  determines which of a number of possible transmit architectures should be enabled, depending on the communication standard being used. The transmit definition software  300  then enables the appropriate components within the software defined transmit architecture  200  to enable communication in the desired standard. 
   The transmit definition software  300  also determines the proper format for the data to be transmitted. As will be described in greater detail below, the data is generally formatted by the baseband subsystem  110  into in-phase (I) and quadrature (Q) components. The I and Q signals may take different forms and be formatted differently depending upon the communication standard being employed. Because the software defined transmit architecture  200  is capable of multiple transmit methodologies, the transmit definition software  300  is capable of formatting the data to suit each of the available transmit methodologies. 
   Upconverter  154  supplies the modulated signal via connection  158  to power amplifier  160 . Power amplifier  160  amplifies the modulated signal on connection  158  to the appropriate power level for transmission via connection  162  to antenna  164 . Illustratively, switch  166  controls whether the amplified signal on connection  162  is transferred to antenna  164  or whether a received signal from antenna  164  is supplied to filter  168 . The operation of switch  166  is controlled by a control signal from baseband subsystem  110  via connection  132 . Alternatively, the switch  166  may be replaced by a filter pair (e.g., a duplexer) that allows simultaneous passage of both transmit signals and receive signals, as known to those having ordinary skill in the art. 
   A portion of the amplified transmit signal energy on connection  162  is supplied via connection  170  to power control element  161 . Power control element  161  may form a closed power control feedback loop to control the output power of power amplifier  160  and may also supply a power control feedback signal via connection  172 . 
   A signal received by antenna  164  will be directed to receive filter  168 . Receive filter  168  will filter the received signal and supply the filtered signal on connection  174  to low noise amplifier (LNA)  176 . Receive filter  168  is a band pass filter, which passes all channels of the particular cellular system in which the portable transceiver  100  is operating. As an example, for a 900 MHz GSM system, receive filter  168  would pass all frequencies from 935.1 MHz to 959.9 MHz, covering all 124 contiguous channels of 200 kHz each. The purpose of this filter is to reject all frequencies outside the desired region. LNA  176  amplifies the very weak signal on connection  174  to a level at which downconverter  178  can translate the signal from the transmitted frequency back to a baseband frequency. Alternatively, the functionality of LNA  176  and downconverter  178  can be accomplished using other elements, such as, for example but not limited to, a low noise block downconverter (LNB). 
   Downconverter  178  receives a frequency reference signal, also called a “local oscillator” signal, or “LO”, from synthesizer  148 , via connection  180 , which signal instructs the downconverter  178  as to the proper frequency to which to downconvert the signal received from LNA  176  via connection  182 . The downconverted frequency is called the intermediate frequency or IF. Downconverter  178  sends the downconverted signal via connection  184  to channel filter  186 , also called the “IF filter.” Channel filter  186  filters the downconverted signal and supplies it via connection  188  to amplifier  190 . The channel filter  186  selects the one desired channel and rejects all others. Using the GSM system as an example, only one of the 124 contiguous channels is actually to be received. After all channels are passed by receive filter  168  and downconverted in frequency by downconverter  178 , only the one desired channel will appear precisely at the center frequency of channel filter  186 . 
   The synthesizer  148 , by controlling the local oscillator frequency supplied on connection  180  to downconverter  178 , determines the selected channel. Amplifier  190  amplifies the received signal and supplies the amplified signal via connection  192  to demodulator  194 . Demodulator  194  recovers the transmitted analog information and supplies a signal representing this information via connection  196  to ADC  134 . ADC  134  converts these analog signals to a digital signal at baseband frequency and transfers the signal via bus  128  to DSP  126  for further processing. 
   As an alternative, the downconverted carrier frequency (IF frequency) at connection  184  may be 0 Hz, in which case the receiver is referred to as a “direct conversion receiver”. In such a case the channel filter  186  is implemented as a low pass filter, and the demodulator  194  may be omitted. 
     FIG. 2  is a block diagram illustrating the software defined transmit architecture  200  of  FIG. 1 . The software defined transmit architecture  200  includes a plurality of components, various combinations of which can be used to transmit data in a number of different transmission standards. For example, the software defined transmit architecture  200  includes components that can be selectively enabled by the transmit definition software  300  ( FIG. 1 ) to transmit signals in the GSM, EDGE/TDMA, and the WCDMA standards. 
   The software defined transmit architecture  200  includes a synthesizer  148  ( FIG. 1 ) that supplies a “local oscillator” (LO) signal via connection  201 . Connection  201  is similar to connections  150  and  156  in  FIG. 1 . The LO signal is supplied to frequency divider  202  and to radio frequency (RF) mixers  216  and  251 . The frequency divider  202  divides the input frequency of the synthesizer  148  by a factor of four (4) and provides the divided frequency output on connections  203 ,  205 , and  271 . A 0° LO signal is supplied on connection  203 , and a 90° LO signal is supplied on connection  205 , while the phase of the LO signal supplied over connection  271  is arbitrary. In a simplified embodiment, either connection  203  or connection  205  can be used in place of connection  271 . As will be described in greater detail with respect to  FIGS. 3 ,  4 , and  5 , the software defined transmit architecture  200  can be used to transmit data signals in any of a number of different transmission standards. Accordingly, a transmission standard specific explanation of each of the components in  FIG. 2  will be provided in  FIGS. 3 ,  4 , and  5 , while only a basic description of the components will be provided with regard to  FIG. 2 . 
   Although omitted for simplicity, each of the components in the software defined transmit architecture  200  includes a connection to the control signals line  132  of  FIG. 1 . The control signal line  132  provides a signal, typically generated by the transmit definition software  300 , that enables and activates the particular components within the software defined transmit architecture  200 , depending on the desired transmission standard. 
   The exemplary software defined transmit architecture  200  includes components that allow the portable transceiver  100  to communicate using any of the GSM, EDGE/TDMA, and WCDMA transmission standards. Accordingly, either a constant envelope (i.e., one comprising only a PM signal) or a non-constant envelope (i.e., one comprising both a PM signal and an AM signal) output can be provided by the software defined transmit architecture  200 . The GSM standard calls for a constant envelope power output. Therefore, as will be described with respect to  FIG. 2 , only a single transmit chain (i.e., the I/Q modulator  206 , low pass filter  212 , RF mixer  216 , synchronous oscillator  218 , and power amplifier  226  form a transmit chain for GSM) may be used for GSM. 
   However, as will be described below, an EDGE/TDMA transmit signal can be formed by combining the output of the above described transmit chain with the output of the transmit chain formed by the I/Q modulator  241 , low pass filter  247 , RF mixer  251 , synchronous oscillator  254 , and power amplifier  261 . The output of the two transmit chains can be combined using a technique referred to as “out-phasing.” This technique uses the phase difference of two signals that contain only a PM component to develop a signal that includes both a PM component and an AM component, and is described in detail in commonly assigned, co-pending U.S. patent application Ser. No. 10/207,320 entitled “Mirror Translation Loop Transmitter Architecture,” filed on Jul. 29, 2002, now U.S. Pat. No. 7,082,169, issued on Jul. 25, 2006, which is hereby incorporated in its entirety by reference. 
   Alternatively, the two above described transmit chains can also be used for GSM. In such an arrangement, the two chains should always be in phase. The outputs of the two transmit chains are added together to get a higher amplitude output. For example, a 6 dB greater signal and only 3 dB more noise compared to one chain alone. Therefore, in this case the “out-phasing” isn&#39;t being used since the two vectors being added always point the same direction. 
   The software defined transmit architecture  200  includes a phase shifter  245 . The phase shifter  245  may comprise any phase shifter, but in this embodiment, comprises a pair of in-phase (I)/quadrature (Q) (I/Q) modulators  206  and  241 . The output of the frequency divider  202  on connection  205  is supplied to both the I/Q modulator  206  and the I/Q modulator  241 . Depending upon which components are activated by the transmit definition software  300 , the data signal that is to be transmitted via the software defined transmit architecture  200  is supplied to one or both I/Q modulators  206  and  241 . The data is supplied in the form of an in-phase (I) component and a quadrature (Q) component. For example, when transmitting using the GSM communication standard, the I component is supplied via connection  207  to I/Q modulator  206  and the Q component is supplied via connection  208  to I/Q modulator  206 . In the case of EDGE/TDMA (or GSM if the GSM is to combine the output of the two above-defined transmit chains) communication, the I and Q components are also supplied via connections  242  and  244 , respectively, to the I/Q modulator  241 . 
   The output of I/Q modulator  206  is supplied via connection  209  to a low-pass filter  212 . The low-pass filter  212  rejects any third order and higher harmonics present on the signal on connection  209 . The output of the low-pass filter  212  is supplied via connection  214  to the RF mixer  216 . The RF mixer  216  receives the local oscillator (LO) signal via connection  201  from the synthesizer  148  and mixes the two signals to upconvert the signal on connection  214  to a radio frequency (RF) signal on connection  217 . Unfortunately, the RF mixer  216  has a high noise floor, and therefore, it is possible that undesirable spurious emissions (for example, upconversion byproducts that may be spectrally close to the desired frequency) may be emitted from the RF mixer  216 . To reduce the spurious emissions and noise, the output of the RF mixer  216  is supplied to a synchronous oscillator  218 . 
   The synchronous oscillator  218 , the detail of which is disclosed in commonly assigned, co-pending U.S. Utility patent application Ser. No. 10/233,231 entitled “Wireless Transmitter Incorporating a Synchronous Oscillator in a Translation Loop,” filed on Aug. 30, 2002, now U.S. Pat. No. 6,961,547, issued on Nov. 1, 2005, which is hereby incorporated in its entirety by reference, acts as a regenerative receiver, thereby oscillating at the frequency of the signal on connection  217  and rejecting all spurious emission from mixer  216 , thereby providing a clean modulated output signal at the desired RF frequency. 
   The output of the synchronous oscillator  218  is supplied to a switch  221 . The position of the switch  221  determines whether the output of the synchronous oscillator is applied to a mixer (as is the case in WCDMA operation) or directly to a corresponding power amplifier (as is the case in GSM or EDGE/TDMA operation) via another switch  281 . The operation of the switches  221  and  281  is controlled by a control signal via connection  132  under the direction of the transmit definition software  300  ( FIG. 1 ). The output of synchronous oscillator  218  is directed by switches  221  and  281  directly to the input of power amplifier  226  via connections  222  and  224 . The power amplifier  226  performs the function of the power amplifier  160  of  FIG. 1 . The signal on connection  224  is amplified by power amplifier  226  and supplied as an output via connection  228 . 
   The output of I/Q modulator  241  is supplied via connection  246  to a low-pass filter  247 . The low-pass filter  247  rejects any third order and higher harmonics present on the signal on connection  246  similar to the low-pass filter  212 . The output of the low-pass filter  247  is supplied via connection  248  to the RF mixer  251 . The RF mixer  251  receives the local oscillator (LO) signal via connection  201  from the synthesizer  148  and mixes the two signals to upconvert the signal on connection  248  to a radio frequency (RF) signal on connection  252  in similar fashion to the RF mixer  216 . Similarly, to reduce the spurious emissions on connection  252 , the output of the RF mixer  251  is supplied to a synchronous oscillator  254 , which operates similarly to the synchronous oscillator  218 . 
   The output of the synchronous oscillator  254  is supplied to a switch  256 . The position of the switch  256  determines whether the output of the synchronous oscillator is applied to a mixer (as is the case in WCDMA operation) or directly to a corresponding power amplifier (as is the case in GSM (if both transmit chains are used) or EDGE/TDMA operation) via switch  279 . The operation of the switches  256  and  279  is controlled by a control signal via connection  132  under the direction of the transmit definition software  300  ( FIG. 1 ). The output of synchronous oscillator  254  is directed by switches  256  and  279  directly to the input of power amplifier  261  via connections  257  and  258 . The power amplifier  261  performs the function of the power amplifier  160  of  FIG. 1 . The signal on connection  258  is amplified by power amplifier  261  and supplied as an output via connection  262 . 
   If both transmit chains are used, it is possible to form an amplitude modulated (AM) signal using the phase altered phase modulated signals from the I/Q modulators  206  and  241  as described in the above-referenced U.S. patent application entitled “Mirror Translation Loop Transmitter Architecture.” These signals are supplied as described above to the RF mixers  216  and  251 , and to the synchronous oscillators  218  and  254 . However, the signals that are supplied to the two above described transmit chains are constant in magnitude but have opposite phase deltas for EDGE/TDMA, and constant in magnitude but in phase for GSM if the GSM operation uses both transmit chains. These two signals are amplified by the power amplifiers  226  and  261  the output of which are added together in summing element  268 . The output of the summing element  268  on connection  269  is the combined output of the two transmit chains. If the two transmit chains have received signals that have opposite phase deltas, then the output on connection  269  can include both a PM component and an AM component. Such a transmit methodology is referred to as “out-phasing” as described above. However, if the two transmit chains have received signals that are in phase, both transmit chains can process a signal having the same phase, which, when combined, provides a signal having an improved signal-to-noise ratio. 
   For operation in the WCDMA transmission standard, the output of the frequency divider  202  is also supplied via connection  271  to intermediate frequency (IF) variable gain amplifier (VGA)  272 . Connection  271  may alternatively be either connection  203  or  205 . The IF VGA  272  provides an intermediate frequency non-modulated signal. To satisfy the broad range of amplitude variation of the WCDMA transmit standard, the IF VGA  272  provides a large amount of amplitude range. The IF VGA defines the gain applied to the signal on connection  276 . The output of the IF VGA  272  is supplied via connection  276  to the bandpass filter  277 . The bandpass filter  277  defines a pass band within which the desired IF signal resides. The output of the bandpass filter  277  is supplied via connection  278  to mixers  284  and  288 . The output of the mixer  284  is supplied via connection  224  and switch  281  to amplifier  226  while the output of the mixer  288  is supplied via connection  258  and switch  279  to the amplifier  261 . The switches  279  and  281  are controlled by the control signals  132  under the direction of the transmit definition software  300 , so that when it is desirable to operate in WCDMA mode, the switches direct the outputs of the mixers  288  and  284  to the power amplifiers  261  and  226 , respectively. The operation of the amplifiers  226  and  261  is as described above. 
     FIG. 3  is a block diagram illustrating the components used when the software defined transmit architecture  200  is operating using the GSM standard. The components used for GSM are shown in bold while the other components in the software defined transmit architecture  200  are shown in dotted lines, signifying that they are not used. However, the architecture shown in  FIG. 4 , which describes an embodiment of the invention used for EDGE/TDMA transmission, can also be used for GSM. However, in GSM, the phase of the signals in the two different transmit chains are the same. 
   Assuming that a single transmit chain is used in  FIG. 3 , the synthesizer  148  supplies the local oscillator signal to the frequency divider  202  and to the RF mixer  216  via connection  201 . The output of the frequency divider  202  is supplied to I/Q modulator  206  via connections  203  and  205 . The I and Q signal components supplied via connections  207  and  208  are formatted by the transmit definition software  300  so that they comply with GSM modulation format. 
   The output of the I/Q modulator is supplied via connection  209  to the low-pass filter  212 . The low-pass filter  212  rejects any third order and higher harmonics on connection  209  and supplies a transmit signal on connection  214  to the RF mixer  216 . The RF mixer  216  upconverts the signal on connection  214  to an RF signal on connection  217 . The RF signal on connection  217  is supplied to the synchronous oscillator  218 , which rejects any spurious signals and noise on connection  217  and supplies a clean modulated signal via switch  221 , connection  222  and switch  281  to the power amplifier  226 . In this embodiment, the switches  221  and  281  are controlled by the transmit definition software  300  to direct the output signal directly from the synchronous oscillator  218  to the power amplifier  226 . The power amplifier  226  provides an output signal on connection  228  to an antenna (not shown) of the portable transceiver  100 . A portion of the output of power amplifier  226  is directed via connections  231  and  264  to the power amplifier control “PAC” unit  232 . The power amplifier control unit  232  is a closed loop power control system which provides a power amplifier control signal on connection  234  to the control input  229  of the power amplifier  226 . The output of the power amplifier  226  on connection  228  is the output signal that is directed to the antenna (not shown) of the portable transceiver  100 . 
     FIG. 4  is a block diagram illustrating the components used when the software defined transmit architecture  200  is operating using the EDGE/TDMA standard. The output of the frequency divider  202  is supplied via connections  203  and  205  to both I/Q modulator  206  and I/Q modulator  241 . Each modulator receives both 0° and 90° components of the output of the frequency divider  202 . Because EDGE/TDMA modulation includes both a PM component and an AM component, the above mentioned “out-phasing” technique is employed as described in the above-mentioned commonly assigned co-pending U.S. patent application entitled “Mirror Translation Loop Transmitter Architecture,” to provide both a phase modulated component and an amplitude modulated component in a non-constant envelope transmission format. 
   The signal output from the I/Q modulator  206  on connection  209  differs in phase from the signal output from the I/Q modulator  241  on connection  246 , as determined by the opposite phase delta components applied to each modulator, as described in the above mentioned commonly assigned co-pending U.S. patent application entitled. “Mirror Translation Loop Transmitter Architecture.” These signals are supplied to respective low-pass filters  212  and  247 . The outputs of the low-pass filters  212  and  247  are supplied to respective RF mixers  216  and  251 . The output of the RF mixer  216  is supplied via connection  217  to synchronous oscillator  218  and the output of the RF mixer  251  is supplied via connection  252  to the synchronous oscillator  254 . The synchronous oscillators  218  and  254  reject any spurious signals and noise on connections  217  and  252 , respectively, and supply their respective outputs to respective switches  221  and  256 . 
   The transmit definition software  300  controls the switches  221  and  256  so that the output of the synchronous oscillator  218  is directed, via connection  222  and switch  281 , to the power amplifier  226 , and so that the output of the synchronous oscillator  254  is directed, via connection  257  and switch  279 , to the power amplifier  261 . In this embodiment, the combination of the two power amplifiers  226  and  261  collectively comprise the power amplifier  160  of  FIG. 1 . The output of power amplifier  226  is directed via connection  228  to the summing element  268  while the output of the power amplifier  261  is directed via connection  262  to the summing element  268 . A portion of the output of each power amplifier  226  and  261  is also directed via connection  231  and connection  264  as input to the power amplifier control element  232 . The power amplifier control element  232  provides power amplifier control signals on connections  234  and  267  to the respective control inputs  229  and  266  of power amplifiers  226  and  261 . 
   The summing element  268  combines the output of each power amplifier and provides a combined signal on connection  269 . The combined signal on connection  269  includes both a PM component and an AM component and is directed to the antenna (not shown) of the portable transceiver  100 . 
     FIG. 5  is a block diagram illustrating the components used when the software defined transmit architecture  200  is operating using the WCDMA standard. When used in WCDMA mode, all components of the software defined transmit architecture  200  are enabled. In addition to connections  203  and  205 , the output of the frequency divider  202  is directed via connection  271  to the IF VGA  272 . As mentioned above, the signal on connection  271  may be replaced by either the signal on connections  203  or  205 . As described above, the IF VGA  272  provides an intermediate frequency non-modulated signal having a large amount of amplitude range on connection  276  to the bandpass filter  277 . The bandpass filter  277  passes signals in the desired frequency band onto connection  278 . The connection  278  directs the output of the bandpass filter  277  onto connections  282  and  286  to mixers  284  and  288 , respectively. The transmit definition software  300  causes the switches  221  and  256  to reposition so that the output of the synchronous oscillator  218  is directed onto connection  223  and the output of synchronous oscillator  254  is directed onto connection  259 . The connection  223  directs the output of the synchronous oscillator  218  to the mixer  284  while the connection  259  directs the output of the synchronous oscillator  254  to the mixer  288 . 
   For GSM and EDGE/TDMA, the outputs of synchronous oscillators  254  and  218  are at the transmit frequency. However, for WCDMA the outputs need one more mix to increase the frequency by an amount F UHF /4 to get to the transmit frequency. Note that the WCDMA transmit frequency is a little higher than DCS1800/PCS1900. This is illustrated using the frequency plans in  FIGS. 3 ,  4  and  5 . Note however, that this WCDMA frequency difference is not the only reason to include the mixers  288  and  284 . The mixers  288  and  284  provide a large range of amplitude control, by mixing the fixed-amplitude signal on connections  259  and  223  with a variable-amplitude signal provided by the IF VGA  272 . The “variable amplitude” refers to the average power level to be transmitted. The gain of the IF VGA  272  is set according to the output power desired at the output  269  when operating in WCDMA mode. 
   To illustrate, the gain of the power amplifier can be varied by about 50 dB, which is sufficient for the GSM and EDGE/TDMA systems, but the WCDMA system typically uses 90 dB of range. Therefore, the amplitude of the IF signal is varied by approximately 40 dB by the IF VGA  272 . The IF signal is then mixed in mixers  284  and  288  with the output of the synchronous oscillators  218  and  254 , respectively, before supplying these signals to the power amplifiers  226  and  261 . 
   The mixer  284  combines the low noise RF output of the synchronous oscillator  218  with the output of the bandpass filter  277  on connection  282  and the mixer  288  combines the low noise RF output of the synchronous oscillator  254  with the output of the bandpass filter  277  on connection  286 . 
   The transmit definition software  300  also causes the switches  281  and  279  to reposition so that the output of the mixer  284  is supplied via connection  224  to the power amplifier  226  and the output of the mixer  288  is supplied via connection  258  to the power amplifier  261 . The operation of the power amplifiers  226  and  261  is as described above. It should be noted that for the mixers  284  and  288  to operate properly and provide a low-noise output, the mixer ports should be properly chosen. Each mixer has a “LO” input port and a “small signal” input port. The LO port of mixer  288  is input  259 , and the LO port of mixer  284  is input  223 . The “small signal” port of mixer  288  is input  286 , and the “small signal” port of mixer  284  is input  282 . This is because a synchronous oscillator provides a relatively large constant amplitude signal which is suitable as the LO to the mixer, while the IF VGA  272  provides a variable amplitude signal, which is intended to affect the mixer output amplitude in a proportional fashion. 
   The transmit definition software  300  formats the I and Q signal components depending upon the selected transmit standard. Accordingly the I and Q components will assume different formats depending upon the selected transmit standard. For example, the I and Q signal components will have a different format for GSM, EDGE/TDMA and WCDMA and will also have a different format depending on whether a constant envelope power output or a non-constant envelope power output is provided. 
   As described herein, the software defined transmit architecture  200  extensively reuses existing hardware to support various digital cellular formats. The software defined transmit architecture  200  allows the implementation of the transmit section of a portable transceiver on a single module to achieve high performance at low cost, using a minimal number of components, and using a minimal amount of board space. Utilization of the generally non-linear components described in  FIGS. 2 through 5  to form a near-linear output signal allows the software defined transmit architecture  200  to achieve a significant increase in power efficiency compared to existing transmit architectures when used in WCDMA mode. Importantly, the software defined transmit architecture  200  requires no external surface acoustic wave (SAW) or other filters to support multi-standard, multi-band operation. For operation using the WCDMA standard, the wide dynamic range is achieved without placing any severe linearity requirements on the IF VGA  272 , since the IF VGA  272  amplifies only a non-modulated carrier signal. 
     FIG. 6  is a flow chart  600  describing the operation of the transmit definition software  300  of  FIG. 1 . In block  602  the portable transceiver  100  is initialized. In block  604 , the transmit definition software  300  determines the communication standard under which communication will occur. This can be accomplished by, for example, receiving and decoding a signal from a base station with which the portable transceiver  100  is communicating. During the initialization sequence, the portable transceiver  100  can activate and listen for signals from nearby base stations. The signal received from the base station can include information that determines the transmission standard with which the base station wishes to communicate with the portable transceiver  100 . 
   Alternatively, a user of the portable transceiver  100  can determine the communication standard through interaction with a control input (for example, the keyboard  106  of  FIG. 1 ) associated with the portable transceiver  100 . 
   In block  606  the transmit definition software  300  determines whether the communication standard uses a constant or a non-constant envelope modulation format. If it is determined that a constant envelope modulation format is used, then, in block  612 , the I and Q signals are formatted for the constant envelope modulation format. If it is determined that a non-constant envelope modulation format is used, then, in block  614 , the I and Q signals are formatted for the non-constant envelope modulation format. 
   In block  616 , after the transmission standard has been determined and the I and Q signals have been formatted appropriately, the transmit definition software  300  activates the appropriate components within the software defined transmit architecture  200  based upon the determined communication standard. For example, if the portable transceiver  100  is to communicate using the GSM standard, then, the components shown in  FIG. 3  would be activated by the transmit definition software  300 , using a control signal sent via connection  132  from the baseband subsystem  110  to the RF subsystem  130 . Depending upon the manner in which the system is implemented, the control signals  132  may originate in the DSP  126 , in the ASIC  135 , or from the FPGA  133 . 
   In block  618  the transmit definition software  300  begins transmitting using the appropriate selected components. 
   While various embodiments of the invention have been described, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible that are within the scope of this invention. Accordingly, the invention is not to be restricted except in light of the attached claims and their equivalents.