Patent ID: 8787431

Claim:
A transmitter which outputs a transmission signal, the transmitter comprising: a signal generation section for performing predetermined signal conversion processing on an input signal, and generating first I and Q signals, a phase signal representing a phase component of the input signal, and a first amplitude signal representing a magnitude of the input signal; an IQ mapping section for converting the phase signal into second I and Q signals; a first low-pass filter (LPF) for removing a spurious component from the second I and Q signals; a quadrature modulator for performing quadrature modulation on the second I and Q signals inputted via the first LPF, and outputting a radio frequency signal; an amplitude modulator for performing amplitude modulation on the radio frequency signal with the first amplitude signal, and outputting the transmission signal; and a compensation section for compensating for amplitude modulation/phase modulation (AM/PM) distortion contained in the transmission signal, based on the first I and Q signals, wherein the compensation section includes: a second low-pass filter (LPF) having the same characteristics as those of the first LPF for receiving the first I and Q signals, predicting a variation of an output caused by the first LPF, and removing a spurious component from the first I and Q signals; an amplitude calculation section for calculating a second amplitude signal representing a magnitude of the first I and Q signals inputted via the second LPF; a look-up table (LUT) in which a coefficient corresponding to the magnitude of the second amplitude signal is stored in advance; a control section for reading, from the LUT, the coefficient corresponding to the magnitude of the second amplitude signal, and calculating, based on the read coefficient, a phase compensation amount corresponding to the second amplitude signal; and an adder for adding the phase compensation amount to the phase signal.