Quadrature amplitude modulator with distortion compensation

Abstract

A quadrature amplitude modulator capable of avoiding compensating the linear distortions completely and accurately by a simple configuration. The modulator includes a level signal generation unit for generating level signal for the modulated wave, and a parameter generation unit for determining appropriate values of linear transformation parameters of the linear transformation to be applied to the in-phase and quadrature amplitude input signals according to the level signal. In this modulator, the linear transformation parameters are determined sequentially in such an order that the linear transformation parameters for a DC off-set are determined first, then the linear transformation parameter for an amplitude balance is determined next while compensating distortion due to the DC off-set, and then the linear transformation parameter for an orthogonal phase relationship is determined while compensating distortions due to the DC off-set and the amplitude balance.

Dependencies are inferred from the claim text.