Power control circuit for a radio frequency transmitter

• US 5,862,460 A
• Filed: 09/13/1996
• Issued: 01/19/1999
• Est. Priority Date: 09/13/1996
• Status: Expired due to Fees

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Rich, Randall Wayne
• Primary Examiner(s): Chin, Wellington
• Assistant Examiner(s): Nguyen, Lee
• Application Number:
  US08/713,911
• Time in Patent Office: 858 Days
• Field of Search: 455/115, 455/116, 455/126, 455/69, 455/127, 455/249.1, 455/253.2, 455/254, 330/284, 330/144, 330/279, 375/295, 375/297, 370/335, 370/252, 370/342
• US Class Current: 455/116
• CPC Class Codes: H03G 3/3042 in modulators, frequency-changers, transmitters or power amplifiers transmission power control in bidirectional transmission systems H04W52/04
• CPC Class Codes: H04W 52/10 Open loop power control
• CPC Class Codes: H04W 52/52 using AGC [Automatic Gain Control] circuits or amplifiers

Abstract

A gain controller (130) for a radio frequency (RF) transmitter (102) controls a power level of a signal (123) transmitted within a predetermined range of output power levels. The gain controller (130) provides the first gain control signal (131) and the second gain control signal (133) responsive to an output power level control signal (150). The first gain control signal (131) controls a gain of a first variable gain stage (144) to vary the power level of the transmit signal (115) at an intermediate frequency causing the output power level of the transmit signal (123) to vary over a lower range of the predetermined range of output power levels. The second gain control signal (133) controls a gain of the second variable gain stage (120) to vary the power level of the transmit signal (121) at a radio frequency causing the output power level of the transmit signal (123) to vary over an upper range of the predetermined range of output power levels. The power control circuit (130) is advantageously utilized in a code division multiple access (CDMA) radiotelephone (100) to provide power control over an 85 dB range of power levels while minimizing sideband noise emissions, current drain, and complexity of the RF transmitter (102).

Claims

1. A transmitter for transmitting a transmit signal at a power level within a predetermined range of output power levels, the transmitter comprising:

a signal generator for generating the transmit signal at an intermediate frequency;

a first variable gain stage, coupled to the signal generator, for controlling a power level of the transmit signal at the intermediate frequency responsive to a first gain control signal;

a signal upconvertor, coupled to the first variable gain stage, for converting the frequency of the transmit signal from the intermediate frequency to a radio frequency;

a second variable gain stage, coupled to the signal upconvertor, for controlling the power level of the transmit signal at the radio frequency responsive to a second gain control signal; and

a gain controller, coupled to the first variable gain stage and the second variable gain stage, for providing the first gain control signal and the second gain control signal responsive to an output power level control signal, wherein the first gain control signal controls a gain of the first variable gain stage to vary the power level of the transmit signal at the intermediate frequency causing the output power level of the transmit signal to vary over a lower range of the predetermined range of output power levels, and wherein the second gain control signal controls a gain of the second variable gain stage to vary the power level of the transmit signal at the radio frequency causing the output power level of the transmit signal to vary over an upper range of the predetermined range of output power levels,

wherein the gain controller further comprises;

a crossover circuit for providing continuous output power level control of the transmit signal between the lower range and the upper range of the predetermined range of the output power levels by controlling the first gain control signal and the second gain control signal responsive to the output power level control signal and a crossover threshold signal,

wherein the crossover circuit further comprises;

a first clamp, coupled to receive the output power level control signal and the crossover threshold signal, for producing a first clamp output signal representative of the first gain control signal, wherein a level of the first clamp output signal is clamped to a level of the crossover threshold signal when a level of the output power control signal is greater than the level of the crossover threshold signal, and wherein the level of the first clamp output signal is equal to the level of the output power level control signal when the level of the output power control signal is less than the level of the crossover threshold signal; and

a second clamp, coupled to receive the output power level control signal and the crossover threshold signal, for producing a second clamp output signal representative of the second gain control signal, wherein a level of the second clamp output signal is clamped to a level of the crossover threshold signal when a level of the output power control signal is less than the level of the crossover threshold signal, and wherein the level of the second clamp output signal is equal to the level of the output power level control signal when the level of the output power control signal is greater than the level of the crossover threshold signal.

2. A transmitter according to claim 1 wherein the signal generator further comprises:

a transmit intermediate frequency local oscillator for providing a transmit intermediate frequency local oscillator signal; and

a modulator for modulating the transmit intermediate frequency local oscillator signal with an information signal to produce the transmit signal at the intermediate frequency.

3. A transmitter according to claim 1 wherein the signal upconvertor further comprises:

a transmit radio frequency local oscillator for providing a transmit radio frequency local oscillator signal; and

a mixer for upconverting the transmit signal at the intermediate frequency to the transmit signal at the radio frequency responsive to the transmit radio frequency local oscillator signal.

4. A transmitter according to claim 1 wherein the gain controller further comprises:

a first linear transformer, coupled to receive the first clamp output signal from the first clamp, for converting the first clamp output signal to a first linear transformer output signal representative of the first gain control signal; and

a second linear transformer, coupled to receive the second clamp output signal from the second clamp, for converting the second clamp output signal to a second linear transformer output signal representative of the second gain control signal.

5. A transmitter according to claim 4:

wherein the first linear transformer further comprises;

a first scaler, coupled to receive the first clamp output signal from the first clamp, for scaling the first clamp output signal by a first predetermined factor so that a sensitivity of gain of the first variable gain stage to the output power control signal equals one; and

a first shift circuit, coupled to the first scaler, for shifting the first clamp output signal by a second predetermined factor to produce a first offset between the first clamp output signal and the linear transformer output signal; and

wherein the second linear transformer further comprises;

a second scaler, coupled to the second clamp, for scaling the second clamp output signal by a third predetermined factor so that a sensitivity of gain of the second variable gain stage to the output power control signal equals one; and

a second shift circuit, coupled to the second scaler, for shifting the second clamp output signal by a fourth predetermined factor to produce a second offset between the second clamp output signal and the linear transformer output signal.

6. A transmitter according to claim 4 wherein the gain controller further comprises:

a first predistortion circuit, coupled to the first linear transformer, for predistorting the first gain control signal responsive to the first linear transformer output signal to compensate for nonlinearities in a first transfer function representative of gain as a function of the first gain control signal for the first variable gain stage; and

a second predistortion circuit, coupled to the second linear transformer, for predistorting the second gain control signal responsive to the second linear transformer output signal to compensate for nonlinearities in a second transfer function representative of gain as a function of the second gain control signal for the second variable gain stage.

7. A transmitter for transmitting a transmit signal at a power level within a predetermined range of output power levels, the transmitter comprising:

a signal generator for generating the transmit signal, at an intermediate frequency;

a first variable gain stage, coupled to the signal generator, for controlling a power level of the transmit signal at the intermediate frequency responsive to a first gain control signal;

a signal upconvertor, coupled to the first variable gain stage, for converting the frequency of the transmit signal from the intermediate frequency to a radio frequency;

a second variable gain stage, coupled to the signal upconvertor, for controlling the power level of the transmit signal at the radio frequency responsive to a second gain control signal; and

a gain controller, coupled to the first variable gain stage and the second variable gain stage, for providing the first gain control signal and the second gain control signal responsive to an output power level control signal, wherein the first gain control signal controls a gain of the first variable gain stage to vary the power level of the transmit signal at the intermediate frequency causing the output power level of the transmit signal to vary over a lower range of the predetermined range of output power levels, and wherein the second gain control signal controls a gain of the second variable gain stage to vary the power level of the transmit signal at the radio frequency causing the output power level of the transmit signal to vary over an upper range of the predetermined range of output power levels;

wherein the gain controller further comprises;

a crossover circuit for providing continuous output power level control of the transmit signal between the lower range and the upper range of the predetermined range of the output power levels by controlling the first gain control signal and the second gain control signal responsive to the output power level control signal and a crossover threshold signal,

wherein the crossover circuit further comprises;

a first clamp, coupled to receive the output power level control signal and the crossover threshold signal, for producing a first clamp output signal representative of the first gain control signal, wherein a level of the first clamp output signal is clamped to a level of the crossover threshold signal when a level of the output power control signal is greater than the level of the crossover threshold signal, and wherein the level of the first clamp output signal is equal to the level of the output power level control signal when the level of the output power control signal is less than the level of the crossover threshold signal; and

a second clamp, coupled to receive the output power level control signal and the crossover threshold signal, for producing a second clamp output signal representative of the second gain control signal, wherein a level of the second clamp output signal is clamped to a level of the crossover threshold signal when a level of the output power control signal is less than the level of the crossover threshold signal, and wherein the level of the second clamp output signal is equal to the level of the output power level control signal when the level of the output power control signal is greater than the level of the crossover threshold signal,

wherein the gain controller further comprises;

a first linear transformer, coupled to receive the first clamp output signal from the first clamp, for converting the first clamp output signal to a first linear transformer output signal representative of the first gain control signal; and

a second linear transformer, coupled to receive the second clamp output signal from the second clamp, for converting the second clamp output signal to a second linear transformer output signal representative of the second gain control signal, and

wherein the gain controller further comprises;

a first predistortion circuit, coupled to the first linear transformer, for predistorting the first gain control signal responsive to the first linear transformer output signal to compensate for nonlinearities in a first transfer function representative of gain as a function of the first gain control signal for the first variable gain stage; and

a second predistortion circuit, coupled to the second linear transformer, for predistorting the second gain control signal responsive to the second linear transformer output signal to compensate for nonlinearities in a second transfer function representative of gain as a function of the second gain control signal for the second variable gain stage.

8. A transmitter according to claim 7 wherein the signal generator further comprises:

a transmit intermediate frequency local oscillator for providing a transmit intermediate frequency local oscillator signal; and

a modulator for modulating the transmit intermediate frequency local oscillator signal with an information signal to produce the transmit signal at the intermediate frequency.

9. A transmitter according to claim 7 wherein the signal upconvertor further comprises:

a transmit radio frequency local oscillator for providing a transmit radio frequency local oscillator signal; and

a mixer for upconverting the transmit signal at the intermediate frequency to the transmit signal at the radio frequency responsive to the transmit radio frequency local oscillator signal.

10. A transmitter according to claim 7:

wherein the first linear transformer further comprises;

a first scaler, coupled to receive the first clamp output signal from the first clamp, for scaling the first clamp output signal by a first predetermined factor so that a sensitivity of gain of the first variable gain stage to the output power control signal equals one; and

a first shift circuit, coupled to the first scaler, for shifting the first clamp output signal by a second predetermined factor to produce a first offset between the first clamp output signal and the linear transformer output signal; and

wherein the second linear transformer further comprises;

a second scaler, coupled to the second clamp, for scaling the second clamp output signal by a third predetermined factor so that a sensitivity of gain of the second variable gain stage to the output power control signal equals one; and

a second shift circuit, coupled to the second scaler, for shifting the second clamp output signal by a fourth predetermined factor to produce a second offset between the second clamp output signal and the linear transformer output signal.

11. A transmitter for transmitting a transmit signal at a power level within a predetermined range of output power levels, the transmitter comprising:

a signal generator for generating the transmit signal at an intermediate frequency, wherein the signal generator further comprises;

a transmit intermediate frequency local oscillator for providing a transmit intermediate frequency local oscillator signal; and

a modulator for modulating the transmit intermediate frequency local oscillator signal with an information signal to produce the transmit signal at the intermediate frequency;

a first variable gain stage, coupled to the signal generator, for controlling a power level of the transmit signal at the intermediate frequency responsive to a first gain control signal;

a signal upconvertor, coupled to the first variable gain stage, for converting the frequency of the transmit signal from the intermediate frequency to a radio frequency, wherein the signal upconvertor further comprises;

a transmit radio frequency local oscillator for providing a transmit radio frequency local oscillator signal;

a mixer for upconverting the transmit signal at the intermediate frequency to the transmit signal at the radio frequency responsive to the transmit radio frequency local oscillator signal; and

a second variable gain stage, coupled to the signal upconvertor, for controlling the power level of the transmit signal at the radio frequency responsive to a second gain control signal; and

a gain controller, coupled to the first variable gain stage and the second variable gain stage, for providing the first gain control signal and the second gain control signal responsive to an output power level control signal, wherein the first gain control signal controls a gain of the first variable gain stage to vary the power level of the transmit signal at the intermediate frequency causing the output power level of the transmit signal to vary over a lower range of the predetermined range of output power levels, and wherein the second gain control signal controls a gain of the second variable gain stage to vary the power level of the transmit signal at the radio frequency causing the output power level of the transmit signal to vary over an upper range of the predetermined range of output power levels,

wherein the gain controller further comprises;

a crossover circuit for providing continuous output power level control of the transmit signal between the lower range and the upper range of the predetermined range of the output power levels by controlling the first gain control signal and the second gain control signal responsive to the output power level control signal and a crossover threshold signal,

wherein the crossover circuit further comprises;

a first clamp, coupled to receive the output power level control signal and the crossover threshold signal, for producing a first clamp output signal representative of the first gain control signal, wherein a level of the first clamp output signal is clamped to a level of the crossover threshold signal when a level of the output power control signal is greater than the level of the crossover threshold signal, and wherein the level of the first clamp output signal is equal to the level of the output power level control signal when the level of the output power control signal is less than the level of the crossover threshold signal; and

a second clamp, coupled to receive the output power level control signal and the crossover threshold signal, for producing a second clamp output signal representative of the second gain control signal, wherein a level of the second clamp output signal is clamped to a level of the crossover threshold signal when a level of the output power control signal is less than the level of the crossover threshold signal, and wherein the level of the second clamp output signal is equal to the level of the output power level control signal when the level of the output power control signal is greater than the level of the crossover threshold signal.

12. A transmitter according to claim 11 wherein the gain controller further comprises:

a first linear transformer, coupled to receive the first clamp output signal from the first clamp, for converting the first clamp output signal to a first linear transformer output signal representative of the first gain control signal; and

a second linear transformer, coupled to receive the second clamp output signal from the second clamp, for converting the second clamp output signal to a second linear transformer output signal representative of the second gain control signal.

13. A transmitter according to claim 12:

wherein the first linear transformer further comprises;

a first scaler, coupled to receive the first clamp output signal from the first clamp, for scaling the first clamp output signal by a first predetermined factor so that a sensitivity of gain of the first variable gain stage to the output power control signal equals one; and

a first shift circuit, coupled to the first scaler, for shifting the first clamp output signal by a second predetermined factor to produce a first offset between the first clamp output signal and the linear transformer output signal; and

wherein the second linear transformer further comprises;

a second scaler, coupled to the second clamp, for scaling the second clamp output signal by a third predetermined factor so that a sensitivity of gain of the second variable gain stage to the output power control signal equals one; and

a second shift circuit, coupled to the second scaler, for shifting the second clamp output signal by a fourth predetermined factor to produce a second offset between the second clamp output signal and the linear transformer output signal.

14. A transmitter according to claim 12 wherein the gain controller further comprises:

a first predistortion circuit, coupled to the first linear transformer, for predistorting the first gain control signal responsive to the first linear transformer output signal to compensate for nonlinearities in a first transfer function representative of gain as a function of the first gain control signal for the first variable gain stage; and

a second predistortion circuit, coupled to the second linear transformer, for predistorting the second gain control signal responsive to the second linear transformer output signal to compensate for nonlinearities in a second transfer function representative of gain as a function of the second gain control signal for the second variable gain stage.

15. A code division multiple access (CDMA) radiotelephone comprising:

a receiver for receiving a closed loop correction signal and for generating a received signal strength indication (RSSI) signal; and

a transmitter for transmitting a transmit signal at a power level within a predetermined range of output power levels, the transmitter comprising;

a radiotelephone controller for providing a first gain control signal and a second gain control signal responsive to the output power level control signal, wherein the output power level control signal is a sum of a channel gain adjust signal, the received signal strength indication signal and the closed loop correction signal;

a signal generator for generating the transmit signal at an intermediate frequency;

a first variable gain stage, coupled to the signal generator, for controlling a power level of the transmit signal at the intermediate frequency responsive to a first gain control signal;

a signal upconvertor, coupled to the first variable gain stage, for converting the frequency of the transmit signal from the intermediate frequency to a radio frequency;

a second variable gain stage, coupled to the signal upconvertor, for controlling the power level of the transmit signal at the radio frequency responsive to a second gain control signal; and

a gain controller, coupled to the first variable gain stage and the second variable gain stage, for providing the first gain control signal and the second gain control signal responsive to an output power level control signal, wherein the first gain control signal controls a gain of the first variable gain stage to vary the power level of the transmit signal at the intermediate frequency causing the output power level of the transmit signal to vary over a lower range of the predetermined range of output power levels, and wherein the second gain control signal controls a gain of the second variable gain stage to vary the power level of the transmit signal at the radio frequency causing the output power level of the transmit signal to vary over an upper range of the predetermined range of output power levels,

wherein the gain controller further comprises;

a crossover circuit for providing continuous output power level control of the transmit signal between the lower range and the upper range of the predetermined range of the output power levels by controlling the first gain control signal and the second gain control signal responsive to the output power level control signal and a crossover threshold signal,

wherein the crossover circuit further comprises;

a first clamp, coupled to receive the output power level control signal and the crossover threshold signal, for producing a first clamp output signal representative of the first gain control signal, wherein a level of the first clamp output signal is clamped to a level of the crossover threshold signal when a level of the output power control signal is greater than the level of the crossover threshold signal, and wherein the level of the first clamp output signal is equal to the level of the output power level control signal when the level of the output power control signal is less than the level of the crossover threshold signal; and

a second clamp, coupled to receive the output power level control signal and the crossover threshold signal, for producing a second clamp output signal representative of the second gain control signal, wherein a level of the second clamp output signal is clamped to a level of the crossover threshold signal when a level of the output power control signal is less than the level of the crossover threshold signal, and wherein the level of the second clamp output signal is equal to the level of the output power level control signal when the level of the output power control signal is greater than the level of the crossover threshold signal.

16. A CDMA radiotelephone according to claim 15 wherein the signal generator further comprises:

a transmit intermediate frequency local oscillator for providing a transmit intermediate frequency local oscillator signal; and

a modulator for modulating the transmit intermediate frequency local oscillator signal with an information signal to produce the transmit signal at the intermediate frequency.

17. A CDMA radiotelephone according to claim 15 wherein the signal upconvertor further comprises:

a transmit radio frequency local oscillator for providing a transmit radio frequency local oscillator signal; and

a mixer for upconverting the transmit signal at the intermediate frequency to the transmit signal at the radio frequency responsive to the transmit radio frequency local oscillator signal.

18. A CDMA radiotelephone according to claim 15 wherein the gain controller further comprises:

a first linear transformer, coupled to receive the first clamp output signal from the first clamp, for converting the first clamp output signal to a first linear transformer output signal representative of the first gain control signal; and

a second linear transformer, coupled to receive the second clamp output signal from the second clamp, for converting the second clamp output signal to a second linear transformer output signal representative of the second gain control signal.

19. A CDMA radiotelephone according to claim 18 wherein the first linear transformer further comprises:

a first scaler, coupled to receive the first clamp output signal from the first clamp, for scaling the first clamp output signal by a first predetermined factor so that a sensitivity of gain of the first variable gain stage to the output power control signal equals one; and

a first shift circuit, coupled to the first scaler, for shifting the first clamp output signal by a second predetermined factor to produce a first offset between the first clamp output signal and the linear transformer output signal; and

wherein the second linear transformer further comprises;

a second scaler, coupled to the second clamp, for scaling the second clamp output signal by a third predetermined factor so that a sensitivity of gain of the second variable gain stage to the output power control signal equals one; and

a second shift circuit, coupled to the second scaler, for shifting the second clamp output signal by a fourth predetermined factor to produce a second offset between the second clamp output signal and the linear transformer output signal.

20. A CDMA radiotelephone according to claim 18 wherein the gain controller further comprises:

a first predistortion circuit, coupled to the first linear transformer, for predistorting the first gain control signal responsive to the first linear transformer output signal to compensate for nonlinearities in a first transfer function representative of gain as a function of the first gain control signal for the first variable gain stage; and

a second predistortion circuit, coupled to the second linear transformer, for predistorting the second gain control signal responsive to the second linear transformer output signal to compensate for nonlinearities in a second transfer function representative of gain as a function of the second gain control signal for the second variable gain stage.

21. A method for controlling an output power level of a transmit signal within a predetermined range of output power levels, the method comprising the steps of:

varying a power level of the transmit signal at an intermediate frequency to produce the output power level for the transmit signal within a lower range of the predetermined range of output power levels;

varying a power level of the transmit signal at a radio frequency to produce the output power level for the transmit signal within an upper range of the predetermined range of output power levels;

determining the output power level for the transmit signal; and

comparing the output power level to an output power crossover threshold level;

wherein the step of varying the power level of the transmit signal at an intermediate frequency is performed when the output power level is less than the output power crossover threshold level to produce the output power level for the transmit signal, and

wherein the step of varying the power level of the transmit signal at a radio frequency is performed when the output power level is greater or equal to than the output power crossover threshold level to produce the output power level for the transmit signal.

22. A method according to claim 21:

wherein the power level of the transmit signal at the intermediate frequency is controlled with a first variable gain stage,

wherein the power level of the transmit signal at the radio frequency is controlled with a second variable gain stage, and

wherein the steps of varying the power level of the transmit signal at the intermediate frequency and at the radio frequency further comprises the steps of;

varying a gain of the first variable gain stage and holding a gain of the second variable gain stage over the lower range of the predetermined range of output power levels to produce the output power level for the transmit signal; and

varying a gain of the second variable gain stage and holding a gain of the first variable gain stage over the upper range of the predetermined range of output power levels to produce the output power level for the transmit signal.

23. A method according to claim 22 further comprises the steps of:

adjusting a slope of a gain versus the output power level for the first variable gain stage of the first variable gain stage to a first predetermined value; and

adjusting a slope of a gain versus the output power level for the second variable gain stage of the second variable gain stage to the first predetermined value.

24. A method according to claim 23 further comprises the steps of:

adjusting an offset of the gain versus the output power level for the first variable gain stage of the first variable gain stage to a second predetermined value; and

adjusting an offset of the gain versus the output power level for the second variable gain stage of the second variable gain stage to a third predetermined value;

wherein the gain versus the output power level for the first variable gain stage combines with the gain versus the output power level for the second variable gain stage to produce a substantially linear total gain versus the output power level for the transmitter.

25. A method according to claim 22 further comprising the steps of:

removing nonlinearities in the gain versus the output power level for the first variable gain stage; and

removing nonlinearities in the gain versus the output power level for the second variable gain stage.

26. A method for operating a code division multiple access (CDMA) radiotelephone comprising the steps of:

receiving a closed loop correction signal;

generating a received signal strength indication (RSSI) signal;

generating an output power control signal responsive to the closed loop correction signal, the RSSI signal and a channel gain adjust signal;

transmitting a transmit signal at an output power level within a predetermined range of output power levels responsive to the output power control signal, the step of transmitting further comprising the steps of;

varying a power level of the transmit signal at an intermediate frequency to produce the output power level for the transmit signal within a lower range of the predetermined range of output power levels;

varying a power level of the transmit signal at a radio frequency to produce the output power level for the transmit signal within an upper range of the predetermined range of output power levels;

determining the output power level for the transmit signal; and

comparing the output power level to an output power crossover threshold level;

wherein the step of varying the power level of the transmit signal at an intermediate frequency is performed when the output power level is less than the output power crossover threshold level to produce the output power level for the transmit signal, and

wherein the step of varying the power level of the transmit signal at a radio frequency is performed when the output power level is greater or equal to than the output power crossover threshold level to produce the output power level for the transmit signal.

27. A method according to claim 26:

wherein the power level of the transmit signal at the intermediate frequency is controlled with a first variable gain stage,

wherein the power level of the transmit signal at the radio frequency is controlled with a second variable gain stage, and

wherein the steps of varying the power level of the transmit signal at the intermediate frequency and at the radio frequency further comprises the steps of;

varying a gain of the first variable gain stage and holding a gain of the second variable gain stage over the lower range of the predetermined range of output power levels to produce the output power level for the transmit signal; and

varying a gain of the second variable gain stage and holding a gain of the first variable gain stage over the upper range of the predetermined range of output power levels to produce the output power level for the transmit signal.

28. A method according to claim 27 further comprises the steps of:

adjusting a slope of a gain versus the output power level for the first variable gain stage of the first variable gain stage to a first predetermined value; and

adjusting a slope of a gain versus the output power level for the second variable gain stage of the second variable gain stage to the first predetermined value.

29. A method according to claim 28 further comprises the steps of:

adjusting an offset of the gain versus the output power level for the first variable gain stage of the first variable gain stage to a second predetermined value; and

adjusting an offset of the gain versus the output power level for the second variable gain stage of the second variable gain stage to a third predetermined value;

wherein the gain versus the output power level for the first variable gain stage combines with the gain versus the output power level for the second variable gain stage to produce a substantially linear total gain versus the output power level for the transmitter.

30. A method according to claim 27 further comprising the steps of:

removing nonlinearities in the gain versus the output power level for the first variable gain stage; and

removing nonlinearities in the gain versus the output power level for the second variable gain stage.