Radio frequency power amplifier improvements using pre-distortion of an amplitude modulation power supply

1. An amplitude-modulated radio frequency (RF) power amplifier circuit comprising:

a first amplitude modulation (AM) pre-distortion circuit adapted to:

receive an AM signal; and

pre-distort the AM signal to generate an amplitude-modulated power supply input signal;

an AM power supply comprising a switching power supply and a linear power supply, the AM power supply adapted to:

receive the amplitude-modulated power supply input signal; and

provide an amplitude-modulated power supply output signal based on the amplitude-modulated power supply input signal; and

a power amplifier stage adapted to:

receive an amplitude-modulated RF input signal that is based on the AM signal;

receive the amplitude-modulated power supply output signal to provide power for amplification; and

amplify the amplitude-modulated RF input signal to provide an amplitude-modulated RF output signal.

2. The amplitude-modulated RF power amplifier circuit of claim 1 wherein:

the amplitude-modulated RF power amplifier circuit provides a polar-modulated RF power amplifier circuit;

the amplitude-modulated RF input signal comprises a polar-modulated RF input signal that is based on the AM signal and a phase modulation (PM) signal; and

the amplitude-modulated RF output signal comprises a polar-modulated RF output signal.

3. The amplitude-modulated RF power amplifier circuit of claim 1 wherein:

the amplitude-modulated RF input signal is a single-ended signal; and

the amplitude-modulated RF output signal is a single-ended signal.

4. The amplitude-modulated RF power amplifier circuit of claim 1 further comprising:

an AM modulation circuit adapted to:

receive a pre-distorted AM signal and a first RF signal; and

amplitude modulate the first RF signal based on the pre-distorted AM signal to provide the amplitude-modulated RF input signal; and

a second AM pre-distortion circuit adapted to:

receive the AM signal; and

pre-distort the AM signal to provide the pre-distorted AM signal.

5. The amplitude-modulated RF power amplifier circuit of claim 4 wherein:

the amplitude-modulated power supply input signal is pre-distorted to increase average power efficiency of the power amplifier stage over average power efficiency of the power amplifier stage based on the amplitude-modulated power supply input signal without pre-distortion; and

pre-distortion of the pre-distorted AM signal recovers at least part of any linearity lost due to the pre-distortion of the amplitude-modulated power supply input signal.

6. The amplitude-modulated RF power amplifier circuit of claim 1 further comprising:

an AM modulation circuit adapted to:

receive a gain-corrected AM signal and a first RF signal; and

amplitude modulate the first RF signal based on the gain-corrected AM signal to provide the amplitude-modulated RF input signal;

gain measurement circuitry adapted to:

receive the amplitude-modulated RF input signal;

receive the amplitude-modulated RF output signal;

determine gain of the power amplifier stage based on the amplitude-modulated RF input signal and the amplitude-modulated RF output signal; and

provide a power amplifier stage gain signal based on the gain; and

AM gain correction circuitry adapted to:

receive the AM signal and the power amplifier stage gain signal; and

provide the gain-corrected AM signal based on the AM signal and the power amplifier stage gain signal.

7. The amplitude-modulated RF power amplifier circuit of claim 1 further comprising:

an AM modulation circuit adapted to:

receive a pre-distorted gain-corrected AM signal and a first RF signal; and

amplitude modulate the first RF signal based on the pre-distorted gain-corrected AM signal to provide the amplitude-modulated RF input signal;

gain measurement circuitry adapted to:

receive the amplitude-modulated RF input signal;

receive the amplitude-modulated RF output signal;

determine gain of the power amplifier stage based on the amplitude-modulated RF input signal and the amplitude-modulated RF output signal; and

provide a power amplifier stage gain signal based on the gain;

AM gain correction circuitry adapted to:

receive the AM signal and the power amplifier stage gain signal; and

provide a gain-corrected AM signal based on the AM signal and the power amplifier stage gain signal; and

a second AM pre-distortion circuit adapted to:

receive the gain-corrected AM signal; and

pre-distort the gain-corrected AM signal to provide the pre-distorted gain-corrected AM signal.

8. The amplitude-modulated RF power amplifier circuit of claim 7 wherein the second AM pre-distortion circuit is further adapted to receive the power amplifier stage gain signal and the pre-distorted gain-corrected AM signal is further based on the power amplifier stage gain signal.

9. The amplitude-modulated RF power amplifier circuit of claim 7 wherein the pre-distorted gain-corrected AM signal provides soft-clipping of the amplitude-modulated RF input signal.

10. The amplitude-modulated RF power amplifier circuit of claim 1 wherein a bandwidth of the linear power supply is greater than a bandwidth of the switching power supply.

11. The amplitude-modulated RF power amplifier circuit of claim 1 wherein a bandwidth of the AM signal is greater than a bandwidth of the amplitude-modulated power supply input signal.

12. The amplitude-modulated RF power amplifier circuit of claim 11 wherein the bandwidth of the AM signal is at least two times the bandwidth of the amplitude-modulated power supply input signal.

13. The amplitude-modulated RF power amplifier circuit of claim 1 wherein the amplitude-modulated power supply input signal is pre-distorted to a minimum value when a magnitude of the AM signal is below a minimum threshold.

14. The amplitude-modulated RF power amplifier circuit of claim 1 wherein the amplitude-modulated power supply input signal is pre-distorted to substantially prevent clipping of the amplitude-modulated RF output signal.

15. The amplitude-modulated RF power amplifier circuit of claim 1 wherein the amplitude-modulated power supply input signal is pre-distorted to substantially maintain constant gain in the power amplifier stage.

16. The amplitude-modulated RF power amplifier circuit of claim 1 wherein the amplitude-modulated power supply input signal is pre-distorted to substantially maintain constant linearity in the power amplifier stage.

17. The amplitude-modulated RF power amplifier circuit of claim 1 wherein the amplitude-modulated power supply input signal is pre-distorted to increase average power efficiency of the power amplifier stage:

over the average power efficiency of the power amplifier stage based on the amplitude-modulated power supply input signal without pre-distortion; and

while conforming to linearity constraints.

18. The amplitude-modulated RF power amplifier circuit of claim 17 wherein the amplitude-modulated power supply input signal is pre-distorted to maximize the average power efficiency of the power amplifier stage.

19. The amplitude-modulated RF power amplifier circuit of claim 18 wherein the linearity constraints comprise maximum linearity error limits and linearity error margins.

20. The amplitude-modulated RF power amplifier circuit of claim 17 wherein the linearity constraints comprise adjacent channel leakage power ratio (ACLR) constraints.

21. The amplitude-modulated RF power amplifier circuit of claim 1 further comprising:

an AM modulation circuit adapted to:

receive a gain-corrected AM signal and a first RF signal; and

amplitude modulate the first RF signal based on the gain-corrected AM signal to provide the amplitude-modulated RF input signal;

gain measurement circuitry adapted to:

receive the AM signal;

receive the amplitude-modulated RF output signal;

determine gain of the power amplifier stage based on the AM signal and the amplitude-modulated RF output signal; and

provide a power amplifier stage gain signal based on the gain; and

AM gain correction circuitry adapted to:

receive the AM signal and the power amplifier stage gain signal; and

provide the gain-corrected AM signal based on the AM signal and the power amplifier stage gain signal.

22. The amplitude-modulated RF power amplifier circuit of claim 1 further comprising:

an AM modulation circuit adapted to:

receive a pre-distorted gain-corrected AM signal and a first RF signal; and

amplitude modulate the first RF signal based on the pre-distorted gain-corrected AM signal to provide the amplitude-modulated RF input signal;

gain measurement circuitry adapted to:

receive the AM signal;

receive the amplitude-modulated RF output signal;

determine gain of the power amplifier stage based on the AM signal and the amplitude-modulated RF output signal; and

provide a power amplifier stage gain signal based on the gain;

AM gain correction circuitry adapted to:

receive the AM signal and the power amplifier stage gain signal; and

provide a gain-corrected AM signal based on the AM signal and the power amplifier stage gain signal; and

a second AM pre-distortion circuit adapted to:

receive the gain-corrected AM signal; and

pre-distort the gain-corrected AM signal to provide the pre-distorted gain-corrected AM signal.

23. The amplitude-modulated RF power amplifier circuit of claim 1 wherein the amplitude-modulated power supply input signal is based on at least one of values extracted from a look-up table and interpolation between values in the look-up table.

24. The amplitude-modulated RF power amplifier circuit of claim 23 wherein:

the look-up table comprises a plurality of sub look-up tables;

the first AM pre-distortion circuit is further adapted to select one of the plurality of sub look-up tables based on a target output power of the power amplifier stage; and

the selected one of the plurality of sub look-up tables comprises the values extracted from the look-up table and the values in the look-up table.

25. The amplitude-modulated RF power amplifier circuit of claim 24 wherein the first AM pre-distortion circuit is further adapted to switch the selected one of the plurality of sub look-up tables using a digital ramp.

26. An amplitude-modulated radio frequency (RF) power amplifier circuit comprising:

a first amplitude modulation (AM) pre-distortion circuit adapted to:

receive an AM signal; and

pre-distort the AM signal to provide an amplitude-modulated power supply input signal;

an AM power supply adapted to:

receive the amplitude-modulated power supply input signal; and

provide an amplitude-modulated power supply output signal based on the amplitude-modulated power supply input signal; and

a power amplifier stage adapted to:

receive an amplitude-modulated RF input signal that is based on the AM signal;

receive the amplitude-modulated power supply output signal to provide power for amplification;

amplify the amplitude-modulated RF input signal to provide an amplitude-modulated RF output signal; and

wherein:

the amplitude-modulated RF power amplifier circuit provides an amplitude-modulated quadrature RF power amplifier circuit;

the amplitude-modulated RF input signal comprises:

an in-phase amplitude-modulated RF input signal; and

a quadrature-phase amplitude-modulated RF input signal;

the amplitude-modulated RF output signal comprises:

an in-phase amplitude-modulated RF output signal; and

a quadrature-phase amplitude-modulated RF output signal; and

the power amplifier stage comprises:

an in-phase power amplifier stage adapted to:

receive the in-phase amplitude-modulated RF input signal that is based on the AM signal;

receive the amplitude-modulated power supply output signal to provide power for amplification; and

amplify the in-phase amplitude-modulated RF input signal to provide the in-phase amplitude-modulated RF output signal; and

a quadrature-phase power amplifier stage adapted to:

receive the quadrature-phase amplitude-modulated RF input signal that is based on the AM signal;

receive the amplitude-modulated power supply output signal to provide power for amplification; and

amplify the quadrature-phase amplitude-modulated RF input signal to provide the quadrature-phase amplitude-modulated RF output signal.

27. The amplitude-modulated RF power amplifier circuit of claim 26 wherein the AM power supply comprises a switching power supply.

28. The amplitude-modulated RF power amplifier circuit of claim 27 wherein the AM power supply further comprises a linear power supply.

29. An amplitude-modulated radio frequency (RF) power amplifier circuit comprising:

a first amplitude modulation (AM) pre-distortion circuit adapted to:

receive an AM signal; and

pre-distort the AM signal to generate an amplitude-modulated power supply input signal;

an AM power supply adapted to:

receive the amplitude-modulated power supply input signal; and

provide an amplitude-modulated power supply output signal based on the amplitude-modulated power supply input signal; and

a power amplifier stage adapted to:

receive an amplitude-modulated RF input signal that is based on the AM signal;

receive the amplitude-modulated power supply output signal to provide power for amplification;

amplify the amplitude-modulated RF input signal to provide an amplitude-modulated RF output signal; and

wherein:

the amplitude-modulated RF power amplifier circuit provides a polar-modulated quadrature RF power amplifier circuit;

the amplitude-modulated RF input signal comprises:

an in-phase polar-modulated RF input signal; and

a quadrature-phase polar-modulated RF input signal;

the amplitude-modulated RF output signal comprises:

an in-phase polar-modulated RF output signal; and

a quadrature-phase polar-modulated RF output signal; and

the power amplifier stage comprises:

an in-phase power amplifier stage adapted to:

receive the in-phase polar-modulated RF input signal that is based on the AM signal and a phase modulation (PM) signal;

receive the amplitude-modulated power supply output signal to provide power for amplification; and

amplify the in-phase polar-modulated RF input signal to provide the in-phase polar-modulated RF output signal; and

a quadrature-phase power amplifier stage adapted to:

receive the quadrature-phase polar-modulated RF input signal that is based on the AM signal and the PM signal;

receive the amplitude-modulated power supply output signal to provide power for amplification; and

amplify the quadrature-phase polar-modulated RF input signal to provide the quadrature-phase polar-modulated RF output signal.

30. A method comprising:

receiving an amplitude modulation (AM) signal;

pre-distorting the AM signal to provide an amplitude-modulated power supply input signal;

receiving the amplitude-modulated power supply input signal;

generating an amplitude-modulated power output with an AM power supply based on the amplitude-modulated power supply input signal, wherein the AM power supply comprises a switching power supply and a linear supply;

receiving an amplitude-modulated RF input signal that is based on the AM signal;

receiving the amplitude-modulated power supply output signal to provide power for amplification; and

amplifying the amplitude-modulated RF input signal to provide an amplitude-modulated RF output signal.