Patent ID: 7333562
Filing Date: 2008-02-19
Classification: H03F

Abstract:
1. A predistortion type nonlinear distortion compensating circuit which is placed before a power amplifier having a distortion characteristic, and outputs to said power amplifier a compensation signal obtained by distorting an input signal by a distortion compensation value corresponding to an amplitude of the input signal, comprising: an amplitude converter for calculating an amplitude value of an input signal, converting the calculated amplitude value into N bit digital data, and outputting M upper bits and L remaining lower bits of the N bit digital data; two multipliers each for receiving one of a pair input signals as one input; a complex multiplier for executing a complex arithmetic operation by receiving outputs from said two multipliers as one input and interpolation data as the other input, and outputting the result to said power amplifier; a first memory which stores a nonlinear inverse characteristic of said power amplifier, receives output data having the M upper bits, and outputs a first corresponding value having a value of the M upper bits as an address; a second memory which stores the same nonlinear inverse characteristic of said power amplifier, receives a value obtained by adding 1 to the M upper bit output data, and outputs a sccond corresponding value having a value of the M upper bits+1 as an address; an interpolation circuit for receiving outputs from said first and second memories and output data having the L lower bits, and, on the basis of the inputs, outputting to each of said two multipliers an amplitude component of interpolation data corresponding to the input signal, and outputting a phase component of the interpolation data; and a cos converter and sin converter for convening the phase component output from said interpolation circuit and outputting as the other input to said complex multiplier.