Multi-rate multistage digital compensator for nonlinear systems

A transceiver radio comprising:

• a digital predistortion system connected in series with a power amplifier, the digital predistortion system comprising:
• a plurality of compensator circuits connected in series, wherein each compensator circuit of the plurality of compensator circuits comprises a plurality of nonlinearity processing circuits connected in parallel and configured to implement a transformation function to modify a linearity of an input signal received at a first compensator circuit of the plurality of compensator circuits, and wherein at least one nonlinearity processing circuit of the plurality of nonlinearity processing circuits implements a different transformation function than at least one other nonlinearity processing circuit of the plurality of nonlinearity processing circuits, wherein the transformation function comprises one or more weighted coefficients that are set based on a digital predistortion adaptation circuit configured to determine the one or more weighted coefficients using back propagation;
• and
• an adder circuit configured to sum an output of each nonlinearity processing circuit of the plurality of nonlinearity processing circuits of a last compensator circuit of the plurality of compensator circuits to obtain a digital predistortion signal, wherein the adder circuit is further configured to provide the digital predistortion signal as an input to the power amplifier.

A wireless device comprising:

• an antenna configured to emit a signal received from a power amplifier;
• the power amplifier;
• a transceiver comprising a digital predistortion system connected in series with the power amplifier, the digital predistortion system comprising:
• a plurality of compensator circuits connected in series, wherein each compensator circuit of the plurality of compensator circuits comprises a plurality of nonlinearity processing circuits connected in parallel and configured to implement a transformation function to modify a linearity of an input signal received at a first compensator circuit of the plurality of compensator circuits, and wherein at least one nonlinearity processing circuit of the plurality of nonlinearity processing circuits implements a different transformation function than at least one other nonlinearity processing circuit of the plurality of nonlinearity processing circuits;
• and
• an adder circuit configured to sum an output of each nonlinearity processing circuit of the plurality of nonlinearity processing circuits of a last compensator circuit of the plurality of compensator circuits to obtain a digital predistortion signal, wherein the adder circuit is further configured to provide the digital predistortion signal as an input to the power amplifier;
• a digital predistortion adaptation circuit configured to receive an output of the power amplifier and to configure one or more coefficients of the transformation function of at least one compensator circuit of the plurality of compensator circuits based at least in part on the output of the power amplifier, wherein the digital predistortion adaptation circuit is configured to determine the one or more coefficients using back propagation;
• and
• a coupler configured to provide the output of the power amplifier to the digital predistortion adaptation circuit.