Patent ID: 7248643

Claim:
A distortion compensator comprising: an amplitude-phase controller for controlling an amplitude and phase of an input transmission base-band signal to form a controlled signal; a quadrature modulator for orthogonally modulating the controlled signal received from the amplitude-phase controller; a power amplifier for amplifying the quadrature modulated signal received from the quadrature modulator; a directional coupler for distributing the amplified signal received from the power amplifier as a feedback signal; a frequency converter for frequency-converting the feedback signal received from the directional coupler; a Fourier transformer for Fourier-transforming the frequency-converted signal into a frequency spectrum signal; an out-band power calculator for computing an out-band power outside of a transmission band from the frequency spectrum signal, the out-band power corresponding to a distortion component of the power amplifier; an amplitude calculator for computing an amplitude value of the input transmission base-band signal; fixed-coefficient storage for storing characteristics reverse to a pre-measured input/output characteristic of the power amplifier, one of the stored characteristics selected based on the amplitude value; an error coefficient calculator for computing an error characteristic, the error characteristic computed based on the out-band power from the out-band power calculator and the selected characteristic from the fixed coefficient storage; and an amplitude-phase change calculator for computing an amplitude change and a phase change based on the selected characteristic from the fixed-coefficient storage and the error characteristic from the error coefficient calculator, and instructing the amplitude-phase controller to carry out the control based on the amplitude change and the phase change.