Abstract: A proximity radar is described in which a signal phase modulated in accordance with a pseudorandom sequence is transmitted from an antenna, and a return signal reflected from a target is received by this antenna. The return signal is correlated with a signal identical to the transmitted signal but delayed by a selected time interval. The delay imposed on the transmitted signal as fed to the correlator is alternately given the two values n.t and n'.t where n' is less than n and the time interval n.t corresponds to the time taken by the signal to travel to and return from the target when the radar is at a predetermined distance from the target, which distance is to be detected. The correlator output is fed through an amplifier circuit including an automatic gain control circuit when the delay is n'.t and the automatic gain control circuit is inoperative when the delay is n.t.