RF transceiver front end module with improved linearity

1. A power amplifier system comprising:

a modulator configured to generate a radio frequency transmit signal;

a front end module including a power amplifier configured to amplify the radio frequency transmit signal to generate an amplified radio frequency transmit signal and a coupler positioned between an antenna and the power amplifier, the coupler configured to output a measure of both forward and reverse power associated with the amplified radio frequency transmit signal;

one or more non-volatile memory devices storing an equalizer table having a plurality of entries generated during a pre-characterization of the front-end module under a plurality of characterization states corresponding to different input conditions, the one or more memory devices storing a digital pre-distortion table configured to implement memoryless digital pre-distortion on the radio frequency transmit signal; and

a processor configured to (a) receive voltage standing wave ratio measurements derived from the forward and reverse power output by the coupler, (b) access entries in the equalizer table based at least in part on the voltage standing wave ratio measurements, and (c) prior to amplification of the radio frequency transmit signal by the power amplifier, adjust the radio frequency transmit signal based on the pre-distortion table and the accessed entries from the equalization table to compensate for one or more memory effects present in the power amplifier system.

2. The power amplifier system of claim 1 wherein the equalizer table was generated using a programmable antenna tuner to tune the front end module to desired voltage standing wave ratio points.

3. The power amplifier system of claim 1 wherein the front end module does not include an integrated antenna tuner.

4. The power amplifier system of claim 1 wherein the front end module further includes a programmable antenna tuner positioned between the antenna and the coupler.

5. The power amplifier system of claim 1 wherein the front end module further includes one or more duplexers positioned between the power amplifier and the dual directional coupler and which contribute to at least some of the memory effects.

6. The power amplifier system of claim 4 wherein the programmable antenna tuner is adjustable to tune an impedance seen by the power amplifier in order to provide a coarse correction of non-linearity within the power amplifier system, and the adjustment of the radio frequency transmit signal based on the accessed entries provides fine correction of non-linearity within the power amplifier system.

7. The power amplifier system of claim 1 wherein the coupler is a dual directional coupler.

8. The power amplifier system of claim 1 wherein the processor is further configured to adjust the radio frequency transmit signal by adapting values in the digital pre-distortion table based on the accessed entries in the equalizer table.

9. The power amplifier system of claim 1 further comprising an envelope tracking system configured to provide the power supply control signal to the power amplifier to control a voltage level of the power amplifier based on a shaped envelope signal, the processor further configured to adjust a delay between the RF transmit signal and the supply control signal based on delay values included in the accessed equalizer table entries.

10. A mobile device comprising:

a modulator configured to generate a radio frequency transmit signal;

a front end module including a power amplifier configured to amplify the radio frequency transmit signal to generate an amplified radio frequency signal and a coupler configured to receive the amplified radio frequency signal, the power amplifier configured to receive a power amplifier supply voltage for powering the power amplifier, the coupler configured to output a measure of both forward and reverse power associated with the amplified radio frequency transmit signal;

an antenna configured to transmit the amplified radio frequency signal;

one or more non-volatile memory devices storing an equalizer table having a plurality of entries generated during a pre-characterization of the front-end module under a plurality of characterization states corresponding to different input conditions, the one or more memory devices storing a digital pre-distortion table configured to implement memoryless digital pre-distortion on the radio frequency transmit signal; and

a processor configured to (a) receive voltage standing wave ratio measurements derived from the forward and reverse power output by the coupler, (b) access entries in the equalizer table based at least in part on the voltage standing wave ratio measurements, and (c) prior to amplification of the radio frequency transmit signal by the power amplifier, adjust the radio frequency transmit signal based on the pre-distortion table and the accessed entries to compensate for one or more memory effects present in the power amplifier system.

11. The mobile device of claim 10 wherein the front end module further includes one or more duplexers which contributes to at least some of the one or more memory effects.

12. A power amplifier system comprising:

a front end module including a power amplifier configured to amplify a radio frequency transmit signal to generate an amplified radio frequency transmit signal, a programmable antenna tuner coupled to an antenna, and a coupler positioned between the power amplifier and the antenna tuner, the coupler configured to output a measure of both forward and reverse power associated with the amplified radio frequency transmit signal, the antenna tuner adjustable to tune an impedance seen by the power amplifier in order to provide a coarse correction of non-linearity within the power amplifier system;

one or more non-volatile memory devices storing an equalizer table having a plurality of entries generated during a pre-characterization of the front-end module under a plurality of characterization states corresponding to different input conditions, the one or more memory devices storing a digital pre-distortion table configured to implement digital pre-distortion on the radio frequency transmit signal; and

a processor configured to (a) receive voltage standing wave ratio measurements derived from the forward and reverse power output by the coupler, (b) access entries in the equalizer table based at least in part on the voltage standing wave ratio, and (c) prior to amplification of the radio frequency transmit signal by the power amplifier, adjust the radio frequency transmit signal based on the pre-distortion table and the accessed entries.

13. The power amplifier system of claim 12 wherein the front end module further includes a duplexer.

14. The power amplifier system of claim 12 wherein the duplexer is positioned between the power amplifier and the coupler.

15. The power amplifier system of claim 12 wherein the coupler is a dual directional coupler.

16. The power amplifier system of claim 12 wherein the processor is further configured to adjust the radio frequency transmit signal by adapting values of the digital pre-distortion table based on the accessed entries in the equalizer table.

17. The power amplifier system of claim 12 further comprising an envelope tracking system configured to provide the supply control signal to the power amplifier to control a voltage level of the power amplifier based on a shaped envelope signal and the delay.

18. The mobile device of claim 10 wherein the equalizer table was generated using a programmable antenna tuner to tune the front end module to desired voltage standing wave ratio points.

19. The mobile device of claim 10 wherein the front end module does not include an integrated antenna tuner.

20. The mobile device of claim 10 wherein the front end module further includes a programmable antenna tuner positioned between the antenna and the coupler.