PURPOSE: To discriminate a target from a clutter without using a doppler frequency by repeating various correlation processes to simulate a reflection signal due to the clutter, and subtracting a component of this signal from a video signal so as to remove the clutter.

CONSTITUTION: A video signal which is A/D converted 8 is fed to a correlation process part 10 via a subtracter 9. The process part 10 performs a correlation process (pulse compression for CW) in accordance with a code which is code generated 3 to discriminate signals for each distance for displaying on an indicator 11. The codes which are code generated 3 are transmitted to a delay circuit 12 and, while input codes are shifted in order, are taken out from plural taps. Output from each tap is fed to a multiplier group 13 to be multiplied by a weight appropriate for clutter removal and added 14. Namely, a convolution coding circuit is constituted of the delay circuit 12, the multiplier group 13 and an adder 14, and output thereof is subtracted 9 to remove the clutter. A process result of the process part 10 is mapped 15 for preparing a map for indicating residual intensity and a phase, and after weight renewal 16 it is fed to the multiplier group 13.