Patent US 4,044,356

In a double correlation device incorporated in a radar installation for muring distance, the transmitted high-frequency signal is modulated, by frequency displacement, by a series of pseudo-random pulses. The first correlation is carried out between each pulse of the series and a delayed version of the series, the delay being chosen to correspond to the distance zone to be swept. The resulting signal undergoes a second correlation with the signal received after reflection from the target and controls a switch in order to deduce information on the distance investigated.