Patent ID: 8811917

Claim:
A digital hybrid mode power amplifier system comprising: a down-converted RF input; a multi-channel digital input; a digital predistortion module for receiving at least one of the down-converted RF input or multi-channel digital input, wherein the digital predistortion module utilizes a predistortion polynomial; a power amplifier portion responsive to signals representative of an output of the digital predistortion module; a down-converted feedback portion adapted to monitor signals representative of adjacent channel power for feeding back to the digital predistortion module signals representative of an output of one or more channels of the power amplifier portion, in response to which the digital predistortion module computes the predistortion polynomial and modifies its output to reduce adjacent channel power level; and wherein the digital predistortion module searches locations of a main channel signal to determine a value representative of adjacent channel power, and implements a multi-directional search algorithm comprising evaluation, rotation, expansion, and contraction using the adjacent channel power value or an adjacent channel power ratio as an evaluation function to develop coefficients for modifying its output.