A compact 50GHz band radar system for keeping safe headway and for warning has been developed.

A simple FM-CW is adopted using a varactor tuned Gunn Oscillator and a naffow beam 2° X 2° is obtained by use of a Mill's Cross Antenna System of compact size. A microcomputer interfaced with the radar used to discriminate betwen the valid targets and false targets and to handle the warning algorithm.

An indicator announces audible and visible warnings according to the signal from the microcomputer.

In this paper, an outline of the system, some experimental results of sensitivity tests and road tests are described.