PURPOSE: To detect the object exsisting in the closest distance surely by adding a band-pass filter, detector and level decider to the main body of a FM-CW radar device.

CONSTITUTION: The circuit composed of a band pass filter 20, detector 11 and level decider 12 is added to the main body 1 of a FM-CW radar equipment. Accordingly, in case of there being an object within the range of closer distance than the lower limit for measurement in the main body 1 the beat signal Sb caused between transmitting and receiving radio waves D1, D2 shows the waveform that the wave less than one period becomes discontinuous on each repeating period of the frequency transition and the beat frequency becomes unable to be measured in a frequency measuring instrument 8. The signal Sb is therefore led to the detector 11 through the filter 10 having the frequency zone equivalent to the distance range to detect the object at that time as a pass zone, the voltage signal Vd detected thereof is given to the decider 12 and by comparing with the preset reference level according to the distance range to detect the object there it can be detected whether there is an object within the range of that distance or not.