Patent ID: 6928272
Filing Date: 2005-08-09
Classification: H03F

Abstract:
1. A distortion compensating circuit for compensating distortion occurring in amplifying means equipped for a radio transmission device, comprising: power calculating and amplitude limitation judging means for calculating the power value of a quadrature baseband transmission signal, judging whether the power value thus calculated is not less than a predetermined power threshold value, outputting as a multiplication coefficient such a coefficient that the power value of the quadrature baseband transmission signal is equal to or less than the power threshold value when the power value thus calculated is larger than the power threshold value, and outputting as a multiplication coefficient such a coefficient that the quadrature baseband transmission signal is left unchanged when the power value thus calculated is not larger than the power threshold value; amplitude maximum value limiting means for performing amplitude maximum value limitation based on circular clipping which is implemented by multiplying each of I and Q components of the quadrature baseband transmission signal by the multiplication coefficient from said power calculating and amplitude limitation judging means; error calculation and compensation data renewing unit for performing the error calculation between the quadrature baseband transmission signal after the amplitude thereof has been limited by said amplitude maximum value limiting means and the quadrature baseband signal fed back from the output of said amplifying means to renew distortion compensation data for compensating non-linear distortion; and non-linear distortion compensation calculating means for performing, on the basis of the compensation data from said error calculation and compensation data renewing means, distortion compensation on the quadrature baseband transmission signal after the amplitude thereof has been limited by said amplitude maximum value limiting means.