Patent ID: 7860185

Claim:
A distortion compensating apparatus comprising: an adaptive distortion compensating unit to compensate nonlinear distortion by controlling an input signal of a nonlinear distortion circuit by using an adaptive algorithm so as to reduce an error between a reference signal and a feedback signal from the nonlinear distortion circuit having the nonlinear distortion; an adaptive equalizer connected between the adaptive distortion compensating unit and the nonlinear distortion circuit or to a front part of the adaptive distortion compensating unit; and a calculating unit to calculate an error between the input signal and the feedback signal from the nonlinear distortion circuit, wherein the adaptive equalizer includes a digital filter to form an amplitude characteristic and a phase characteristic of the input signal on the basis of a filter coefficient group that is set to the digital filter; a memory to hold in advance the filter coefficient group to be set to the digital filter; and a control unit to control reading of the filter coefficient group to be set to the digital filter from the memory on the basis of the input signal and the feedback signal from the nonlinear distortion circuit, wherein the control unit controls the filter coefficient group to be read from the memory in accordance with the error between the input signal and the feedback signal from the nonlinear distortion circuit calculated by the calculating unit and to be set to the digital filter, and wherein the calculating unit normalizes the calculated error by using the input signal.