PURPOSE: To remove malignant jamming waves from radar operation by emitting electric waves of varying frequency and large electric power simultaneous with the emission of radar waves.

CONSTITUTION: A radar transmitter/receiver 3 transmits electric waves of frequency f1 through antenna 1 and a jamming wave generator 7 which is a target receives the electric wave, generating electric waves including a jamming wave. At that time, on the part of a searcher, frequency f2 which is different from frequency f1 is emitted at the same time as frequency f1 from a transmitter 4 through an antenna 2. Emission power P2 of frequency f2 then is larger than the emission power P1, that is, for instance, it is set in a wave form 11 or 21. Consequently, electric wave generated on the jamming side 7 becomes a component of the frequency f2. By interrupting the said component at the transmitter/receiver 3 with the help of a fiter, etc., it is possible to normalize a detection action of the radar frequency f1.