Abstract: A bistatic Doppler radar intrusion detection system which utilizes a high duty-cycle phase-coded pulse compression signal to provide a range-gated detection zone is described. The combined transmit and receive antenna beam patterns define the shape of the detection zone in azimuth and elevation. The distance from the antennas to the detection zone and depth of the detection zone are determined by the pulse compression code sequence selections. The system consists of a transmitter having a code sequence generator for generating one of a selected number of codes and a code sequence. An antenna transmits the modulated signal through the detection zone. A programmable digital delay circuit is used to provide a delayed replica of the code sequence and thereby specify the detection zone range. A receiver is provided having an antenna for receiving signals scattered from the detection zone.