Predistortion in a linear transmitter using orthogonal kernels

A method for compensating for distortion caused by a power amplifier in a radio frequency (RF) transmitter, the method comprising:

• obtaining an output signal sample that depends on an output signal of the power amplifier;
• removing the in-band distortion from said output signal sample to form a modified output signal sample;
• calculating predictor variables from said modified output signal sample, said predictor variables being orthogonal to each other;
• obtaining an input signal sample that depends on an input signal to the power amplifier;
• determining a complex predistortion gain by forming a filter block model, wherein the filter block model receives said predictor variables and outputs the input signal sample, wherein said complex predistortion gain is a function of a complex gain of the filter block model;
• and
• applying said complex predistortion gain to a modulation signal sample to obtain a predistorted signal sample, wherein said complex predistortion gain compensates for distortion caused by the power amplifier when said power amplifier amplifies the input signal, said input signal being dependent on said predistorted signal sample.

A system for compensating for distortion caused by a power amplifier in a radio frequency (RF) transmitter, the system comprising:

• means for obtaining an output signal sample that depends on an output signal of the power amplifier;
• means for removing the in-band distortion from said output signal sample to form a modified output signal sample;
• means for calculating predictor variables from said modified output signal sample, said predictor variables being orthogonal to each other;
• means for obtaining an input signal sample that depends on an input signal to the power amplifier;
• means for determining a complex predistortion gain by forming a filter block model, wherein the filter block model receives said predictor variables and outputs the input signal sample, wherein said complex predistortion gain is a function of a complex gain of the filter block model;
• and
• means for applying said complex predistortion gain to a modulation signal sample to obtain a predistorted signal sample, wherein said complex predistortion gain compensates for distortion caused by the power amplifier when said power amplifier amplifies the input signal, the input signal being dependent on said predistorted signal sample.

A system for compensating for distortion caused by a power amplifier in a radio frequency (RF) transmitter, the system comprising:

• means for obtaining an output signal sample that depends on an output signal of the power amplifier,
• means for calculating predictor variables from said output signal sample, said predictor variables being orthogonal to each other;
• means for obtaining an input signal sample that depends on an input signal to the power amplifier;
• means for determining a complex predistortion gain by forming a filter block model, wherein the filter block model receives said predictor variables and outputs the input signal sample, wherein said complex predistortion gain is a function of a complex gain of the filter block model;
• and
• means for applying said complex predistortion gain to a modulation signal sample to obtain a predistorted signal sample, wherein said complex predistortion gain compensates for distortion caused by the power amplifier when said power amplifier amplifies the input signal, the input signal being dependent on said predistorted signal sample.

A radio frequency (RF) transmitter comprising:

• a predistorter coupled to receive a digital data signal;
• a digital-to-analog converter coupled to the predistorter;
• a power amplifier coupled to the digital-to-analog converter;
• an analog-to-digital converter coupled to the output of the power amplifier;
• a trainer coupled to the analog-to-digital converter and the predistorter and to receive the digital data signal, wherein the trainer is configured to determine a complex predistortion gain as a function of orthogonal predictor variables and to configure the predistorter with the complex predistorter gain.