PURPOSE: To obtain a signal in which a spurious is canceled by phase-detecting part of power of a transmission source signal and part of power of a power amplifier output signal, level-regulating it, phase-inverting it, and adding it to a video signal.

CONSTITUTION: A detector 20 receives a detection signal 15 and a transmission signal 18, and phase-detects it. A level regulator 22 receives a detector output signal 21 from the detector 20, and equalizes the level of the output to that of a video signal 8 by an AGC signal. A power amplifier 3 receives the interference of noise from a power source, etc., adds a spurious to a power amplifier output signal 4, the signal 4 becomes a reflected wave 7 having a reflected wave by a moving target and a reflected wave by a ground surface having a spurious are mixed, and is output as a video signal 11. On the other hand, signals 15, 18 are detected by the detector 20 as a detector output signal 21, which is level-regulated by a regulator 22, output as a spurious video signal 23, and phase inverted by a phase inverter 24. Then, its differential signal 25 is added to the signal 22 to obtain a signal in which a spurious is canceled.