Patent ID: 7215717

Claim:
A distortion compensation circuit comprising: an amplitude computation section that computes an amplitude value of an orthogonal baseband signal; an error computation and compensation data updating section that updates distortion compensation data by obtaining an error between the orthogonal baseband transmission signal and a feedback orthogonal baseband signal obtained by demodulating part of an output from an amplification means, and by computing new distortion compensation data by adding, to distortion compensation data before updating, a value obtained by multiplying the obtained error data by a step coefficient; and a nonlinear distortion compensation computation section that compensates for distortion on the orthogonal baseband transmission signal based on the distortion compensation data from said error computation and compensation data updating section, wherein said error computation and compensation data updating section comprises step coefficient changing means for changing the step coefficient according to the amplitude value computed by said amplitude computation section; and wherein said step coefficient changing means comprises: a step coefficient selector that selects one of at least two step coefficients and outputs the selected step coefficient; and an amplitude determination section that controls a selecting operation of said step coefficient selector according to the amplitude value computed by said amplitude computation section.