Patent ID: 7020447

Claim:
A distortion compensation method for correcting distortion of a transmission power amplifier in a radio apparatus, comprising: storing, in memory, distortion compensation coefficients for correcting distortion of the transmission power amplifier; each of which conforms to a transmit signal and a past transmit signal proceeding the transmit signal; converting a transmit signal to a quadrature signal composed of an in-phase component and a quadrature component; reading a distortion compensation coefficient, which conforms to a present transmit signal and a past transmit signal, out of the memory in complex form; applying distortion compensation processing to said quadrature signal by adding a real part and an imaginary part of said distortion compensation coefficient to each of the signal components of said quadrature signal; applying quadrature modulation to the distortion-compensated quadrature signal, amplifying the quadrature-modulated signal by the transmission power amplifier and transmitting the amplified signal; eliminating phase rotation, which has been produced by said amplifier, from an output signal of the transmission power amplifier; demodulating the signal from which said phase rotation has been eliminated; and updating the real part and the imaginary part of said distortion compensation coefficient in such a manner that a difference between in-phase components and a difference between quadrature components of the quadrature signal before distortion compensation and of the demodulated signal will become zero.