Patent ID: 7496334
Filing Date: 2009-02-24
Classification: H03F,H04B,H04L

Abstract:
1. A transmitter comprising: an amplitude calculating unit which calculates an amplitude of an input modulating signal; a distortion compensation data storage unit which stores distortion data on a normal characteristic or a reverse characteristic to carry out a distortion compensation for the input modulating signal; a distortion compensating unit which reads the distortion data on the normal characteristic or the reverse characteristic from the distortion compensation data storage unit based on an output of the amplitude calculating unit and multiplies or divides the input modulating signal and the distortion data to carry out the distortion compensation; a quadrature modulating unit which carries out a quadrature modulation in response to an output of the distortion compensating unit; a variable gain amplifying unit which amplifies an output of the quadrature modulating unit to control a gain based on a gain control signal; a power amplifying unit which serves to carry out a power amplification for an output of the variable gain amplifying unit and has a linear mode for carrying out the power amplification by using a linear operating region in an input/output power characteristic and a saturation mode for carrying out the power amplification by using a saturation operating region in the input/output power characteristic; and an amplitude modulating unit which inputs an amplitude component of the output of the distortion compensating unit to an output controlling input terminal of the power amplifying unit, thereby carries out a polar coordinate modulation, wherein the input modulating signal and the distortion data on the normal characteristic are multiplied or the input modulating signal and the distortion data on the reverse characteristic are divided in the distortion compensating unit in the case in which the power amplifying unit is operated in the saturation mode to carry out the polar coordinate modulation, and the input modulating signal and the distortion data on the normal characteristic are divided or the input modulating signal and the distortion data on the reverse characteristic are multiplied in the distortion compensating unit in the case in which the power amplifying unit is operated in the linear mode to carry out a linear amplification.