Abstract: This radar system comprises an emitter (3, 4, 5) for the transmission of coherent non-equidistant pulses forming a periodic pattern and being distinguished from each other by a phase modulation according to different quasi-orthogonal laws, the average interval between pulses being of the order of magnitude of the minimum duration of the flashes. For reception, the system comprises a single receiver (7) and a device (8) for coherent elimination of the clutter and echoes of the target bodies, followed by N processing channels for pulse compression (9.1 to 9.N) by correlation with the particular phase modulation laws. The outputs from the processing channels are sent to a device (11) for elimination of secondary peaks due to partial ambiguities.The invention applies to radar surveillance systems for helicopter detection.