Abstract: A device for distance measurement by radar comprises a frequency modulated radar-transmitter and -receiver (10) by which a radar beam is directed onto an object to be measured and in which by mixing the transmitted and the received frequency a beat signal (30) is obtained. By use of frequency modulation (16) the frequency of the transmitted radar signal of the radar-transmitter and -receiver is variable periodically according to a saw tooth function. The frequency of the beat signal, due to the travel time of the radar signal reflected by the object, represents a measured value for the distance of the object. A signal processing circuit generates from the beat signal obtained a measured value of the distance. For this purpose the beat signal is fed into a phase control circuit or phase locked loop circuit (66) the output frequency of which makes the measured value of distance.

Abstract: In order to produce relative velocity signals in accordance with the relative velocity between a following and a preceding vehicle, a Doppler signal transmitter, which targets the preceding vehicle, is attached to the following vehicle. The thus obtained Doppler signals impinge on a signal processor which analyzes the frequency spectrum of the Doppler signal. Velocity signals are formed from the frequencies within this frequency spectrum, which frequencies lie outside the range of those frequencies caused by the velocity of the following vehicle moving relative to the surface.