Adaptive compensation of nonlinear frequency distortion in polar transmitters based on a least squares estimation

A communication system comprising:

• a converter configured to provide a phase components signal and an amplitude components signal;
• an interpolation component configured to generate an amplitude modulation signal from the amplitude components signal;
• a digital to analog converter configured to generate an amplitude carrier modulation signal from the amplitude modulation signal;
• a phase to frequency converter configured to generate a phase modulation signal from the phase components signal;
• a compensation unit having one or more inputs, the compensation unit configured to receive one or more input signals and generate a correction signal according to the one or more input signals, wherein the one or more input signals include amplitude samples of the amplitude modulation signal and wherein the correction signal accounts for distortions from the amplitude modulation signal;
• a summation component configured to receive the phase modulation signal and the correction signal and to generate a corrected phase modulation signal there from;
• a digital phase locked loop configured to receive the corrected phase modulation signal and to generate a phase carrier modulation signal;
• and
• a mixer to mix the phase carrier modulation signal and the amplitude carrier modulation signal into an output transmit signal.

A method of estimating distortion in a communication system, the method comprising:

• obtaining ramp samples of a first portion of a communication sequence;
• obtaining frequency deviation samples of the first portion of the communication sequence;
• developing a distortion estimate according to the ramp samples and the frequency deviation samples, wherein the distortion estimate estimates phase distortion resulting from an amplitude modulation path;
• and
• generating a correction signal according to the distortion estimate and magnitude samples of a data portion of the communication sequence.