PURPOSE: To control the emergence of chaff by reading selectively the chaff pattern data and at the same time to produce a pseud echo corresponding to an actual echo by multiplying the pattern data by the chaff intensity data.

CONSTITUTION: A chaff pattern data is stored in a chaff pattenr ROM17, and then the chaff pattern data is read in accordance with the diffusion of a chaff echo to be shifted to shift registers 18 and 19. The 1st intra-range detecting circuit 20 controls the register 18 and the chaff emergence range in the azimuth; and the 2nd intrarange detecting circuit 21 controls the register 19 and then the chaff emergence range in the distance direction. Then the chaff pattern is delivered in the from of a series signal, superposed on the analog signal given from a converter 22 through a synthesizer 23 and turned into a chaff echo display video signal to be led to a radar indicator, etc. In such a way, a pseudo echo can be produced in accordance with the lapse of time of an actual chaff echo.