Patent ID: 7242247

Claim:
A distortion compensating circuit which detects distortion components generated in a power amplifying circuit amplifying power of a high frequency input signal according to an output signal and an input signal of the power amplifying circuit, and generates a distortion compensating signal according to the detected distortion components, said distortion compensating circuit comprising: a first adjustment circuit which adjusts the input signal and the output signal to an appropriate level; a second adjustment circuit which adjusts the input signal and the output signal to an appropriate phase; a third adjustment circuit which adjusts the input signal and the output signal to an appropriate delay; a distortion coefficient detection circuit which calculates an error signal representing the difference between the adjusted input signal and output signal, and calculates, from the calculated error signal and the input signal, at least a coefficient, specific to the power amplifying circuit, of a third-order intermodulation distortion partly constituting the detected distortion components and additionally a coefficient, specific to the power amplifying circuit, of a fifth-order intermodulation distortion partly constituting the detected distortion components and a coefficient, specific to the power amplifying circuit, of a seventh-order intermodulation distortion partly constituting the detected distortion components; a first distortion compensating signal generating circuit which generates, according to the calculated coefficients, a distortion compensating signal which is characteristically opposite in phase and gain to the intermodulation distortions; a variable delay filter which passes either the generated distortion compensating signal or the input signal based on a location of the variable delay filter; and a first multiplier which multiplies the signal passing through said variable delay filter by the input signal, if the variable delay filter passes the generated distortion compensating signal, or multiplies the signal passing through said variable delay filter by the generated distortion compensating signal, if the variable delay filter passes the input signal, and outputs a signal, which is the signal passing through said variable delay filter multiplied by either the input signal or the generated distortion compensating signal, to said power amplifying circuit.