PURPOSE: To considerably reduce the effect of nonlinear distortion of a power amplifier by detecting a difference between the waveform of a transmission pulse just before the storage in a waveform memory and the waveform of a generated reference pulse and correcting the reference pulse based on the detected difference.

CONSTITUTION: A pulse component is stored in a waveform memory as a pulse waveform in a timing signal from a timing control circuit 8 and when a trigger pulse instructing the transmission of a succeeding pulse is inputted to an input terminal 103, a waveform comparison correction waveform generating section 6 compares the waveform of the pulse sent just before with a reference pulse and generates a pulse correcting its difference and feeds the result to a modulator 7. The output of the modulator 7 is modulated and amplified by a power amplifier 1 and the result is outputted. Thus, the waveform of the transmission pulse is more closer to the reference pulse waveform.