PURPOSE: To prevent the influence of reflection, etc., from appearing at an antenna and a transmission system by separating the point of time of beam scanning from a beam irradiation time, i.e. pulse transmission time in terms of time.

CONSTITUTION: Transmit pulses generated by a transmitter 2 are controlled with a beam irradiation signal sent from a beam irradiation control circuit 8. Then, the driving of a phase shifter driver 7 is controlled with a phase control trigger signal from the beam irradiation control circuit 8 as well, so the phase of a phase shifter 5 is set after the transmit pulses are ceased. A receiver 11 receives reflected pulses from a target through the antenna 6, the phase shifter 5, a power distributing and combining device 4, and a duplexer 3. A signal processing circuit 9 variess a beam scanning trigger, i.e. beam irradiation time and the repetitive period of a transmit trigger generator 1 to prevent the phase shifter 5 from being driven during beam irradiation, improving the S/N.