Digital polar transmitter

1. A digital polar transmitter, comprising:

a baseband processor configured to receive an input signal and to convert the input signal into a baseband amplitude component and a baseband phase component;

a phase modulator in communication with the baseband processor, wherein the phase modulator is configured to modulate an RF carrier signal based on the phase component and to generate a phase-modulated RF carrier signal;

a power amplifier in communication with the baseband processor and the phase modulator, wherein the power amplifier is configured to amplify the phase-modulated RF carrier signal based on the baseband amplitude component and to generate an amplified RF signal; and

a digital feedback loop in communication with the power amplifier and the baseband processor, wherein the digital feedback loop is configured to detect the amplified RF signal and the phase-modulated RF carrier signal, and to provide a digital amplitude feedback signal and a digital phase feedback signal to the baseband processor, based upon the amplified RF signal and the phase-modulated RF carrier signal.

2. A digital polar transmitter as in claim 1 , wherein the baseband processor further comprises:

a symbol processor configured to receive a plurality of digital data symbols and to process each of the plurality of digital data symbols into a baseband amplitude signal and a baseband phase signal; and

an amplitude/phase processor in communication with the symbol processor and configured to pre-distort the baseband amplitude signal and to pre-distort the baseband phase signal.

3. A digital polar transmitter as in claim 1 , wherein the baseband processor further comprises:

a phase predictor configured to operate during a closed-loop calibration period and to provide a closed-loop phase correction signal based on predicted changes in the phase of the amplified RF signal;

a phase correction lookup table configured to store a plurality of phase pre-distortion values and to provide an open-loop phase correction signal based on at least one of the plurality of phase pre-distortion values;

a phase interpolator configured to operate during the closed-loop calibration period and to generate the plurality of phase pre-distortion values; and

a phase synchronizer configured to operate during the closed-loop calibration period and during an open-loop operation period, wherein the phase synchronizer is further configured to pre-distort the baseband phase signal based on the closed-loop phase correction signal during the closed-loop calibration period and to pre-distort the baseband phase signal based on the open-loop phase correction signal during the open-loop operation period.

4. A digital polar transmitter as in claim 1 , wherein the baseband processor further comprises:

an amplitude predictor configured to operate during a closed-loop calibration period and to provide a closed-loop amplitude correction signal based on predicted changes in the amplitude of the amplified RF signal;

an amplitude correction lookup table configured to store a plurality of amplitude pre-distortion values and to provide an open-loop amplitude correction signal based on at least one of the plurality of amplitude pre-distortion values;

an amplitude interpolator configured to operate during the closed-loop calibration period and to generate the plurality of amplitude pre-distortion values; and

an amplitude synchronizer configured to operate during the closed-loop calibration period and during an open-loop operation period, wherein the amplitude synchronizer is further configured to pre-distort the baseband amplitude signal based on the closed-loop amplitude correction signal during the closed-loop calibration period and to pre-distort the baseband amplitude signal based on the open-loop amplitude correction signal during the open-loop operation period.

5. A digital polar transmitter as in claim 1 , wherein the digital feedback look further comprises:

a detector configured to convert the amplified RF signal to a pair of digital IQ feedback signals; and

an IQ to polar converter in communication with the detector and configured to convert the digital IQ feedback signals to the digital amplitude feedback signal and the digital phase feedback signal.

6. A digital polar transmitter as in claim 1 , wherein the power amplifier further comprises:

a plurality of amplifier drivers, wherein each of the plurality of amplifier drivers is configured to generate an amplifier driver amplitude signal based on the baseband amplitude component; and

a plurality of power amplifier stages, each associated with a respective one of the plurality of amplifier drivers, wherein each of the plurality of power amplifier stages is configured to amplify the phase-modulated RF carrier signal based on a respective one of the amplifier driver amplitude signals.

7. A digital polar transmitter, comprising:

a baseband processor configured to receive an input signal and to convert the input signal into a baseband amplitude component and a baseband phase component;

a phase modulator in communication with the baseband processor, wherein the phase modulator is configured to modulate an RF carrier signal based on the phase component and to generate a phase-modulated RF carrier signal;

a power amplifier in communication with the baseband processor and the phase modulator, wherein the power amplifier is configured to amplify the phase-modulated RF carrier signal based on the baseband amplitude component and to generate an amplified RF signal; and

a digital feedback loop in communication with the power amplifier and the baseband processor, wherein the digital feedback loop is configured to detect the amplified RF signal and to provide a digital amplitude feedback signal and a digital phase feedback signal to the baseband processor;

the baseband processor comprising

a phase predictor configured to operate during a closed-loop calibration period and to provide a closed-loop phase correction signal based on predicted changes in the phase of the amplified RF signal,

a phase correction lookup table configured to store a plurality of phase pre-distortion values and to provide an open-loop phase correction signal based on at least one of the plurality of phase pre-distortion values,

a phase interpolator configured to operate during the closed-loop calibration period and to generate the plurality of phase pre-distortion values, and

a phase synchronizer configured to operate during the closed-loop calibration period and during an open-loop operation period, wherein the phase synchronizer is further configured to pre-distort the baseband phase signal based on the closed-loop phase correction signal during the closed-loop calibration period and to pre-distort the baseband phase signal based on the open-loop phase correction signal during the open-loop operation period.

8. A digital polar transmitter as in claim 7 , wherein the digital feedback look further comprises:

a detector configured to convert the amplified RF signal to a pair of digital IQ feedback signals; and

an IQ to polar converter in communication with the detector and configured to convert the digital IQ feedback signals to the digital amplitude feedback signal and the digital phase feedback signal.

9. A digital polar transmitter as in claim 7 , wherein the power amplifier further comprises:

a plurality of amplifier drivers, wherein each of the plurality of amplifier drivers is configured to generate an amplifier driver amplitude signal based on the baseband amplitude component; and

a plurality of power amplifier stages, each associated with a respective one of the plurality of amplifier drivers, wherein each of the plurality of power amplifier stages is configured to amplify the phase-modulated RF carrier signal based on a respective one of the amplifier driver amplitude signals.

10. A digital polar transmitter, comprising:

a baseband processor configured to receive an input signal and to convert the input signal into a baseband amplitude component and a baseband phase component;

a phase modulator in communication with the baseband processor, wherein the phase modulator is configured to modulate an RF carrier signal based on the phase component and to generate a phase-modulated RF carrier signal;

a power amplifier in communication with the baseband processor and the phase modulator, wherein the power amplifier is configured to amplify the phase-modulated RF carrier signal based on the baseband amplitude component and to generate an amplified RF signal; and

a digital feedback loop in communication with the power amplifier and the baseband processor, wherein the digital feedback loop is configured to detect the amplified RF signal and to provide a digital amplitude feedback signal and a digital phase feedback signal to the baseband processor;

the baseband processor comprising

an amplitude predictor configured to operate during a closed-loop calibration period and to provide a closed-loop amplitude correction signal based on predicted changes in the amplitude of the amplified RF signal,

an amplitude correction lookup table configured to store a plurality of amplitude pre-distortion values and to provide an open-loop amplitude correction signal based on at least one of the plurality of amplitude pre-distortion values,

an amplitude interpolator configured to operate during the closed-loop calibration period and to generate the plurality of amplitude pre-distortion values, and

an amplitude synchronizer configured to operate during the closed-loop calibration period and during an open-loop operation period, wherein the amplitude synchronizer is further configured to pre-distort the baseband amplitude signal based on the closed-loop amplitude correction signal during the closed-loop calibration period and to pre-distort the baseband amplitude signal based on the open-loop amplitude correction signal during the open-loop operation period.

11. A digital polar transmitter as in claim 10 , wherein the digital feedback look further comprises:

a detector configured to convert the amplified RF signal to a pair of digital IQ feedback signals; and

an IQ to polar converter in communication with the detector and configured to convert the digital IQ feedback signals to the digital amplitude feedback signal and the digital phase feedback signal.

12. A digital polar transmitter as in claim 10 , wherein the power amplifier further comprises:

a plurality of amplifier drivers, wherein each of the plurality of amplifier drivers is configured to generate an amplifier driver amplitude signal based on the baseband amplitude component; and

a plurality of power amplifier stages, each associated with a respective one of the plurality of amplifier drivers, wherein each of the plurality of power amplifier stages is configured to amplify the phase-modulated RF carrier signal based on a respective one of the amplifier driver amplitude signals.