Abstract: A synthetic aperture radar system is provided in which the receive beam is controlled as to its directivity so that it moves over a required swathe in accordance with the direction of reflection of an interrogating radar pulse over that swathe. In a specific example a receiving array of linear feeds has its outputs connected to respective variable phase shifters which are controlled in dependence upon the predicted relationship between the direction from which reflected energy due to a transmitted pulse will be received and the time elapsed from the transmission of said pulse. The outputs from the variable phase shifters are combined and applied to a receiver.

Abstract: The invention provides a side-looking radar for use on a moving carrier and for exploring space laterally with respect to the displacement direction of the carrier. The receiver includes a non-coherent detector having a reference signal input. The average differential phase between the phases of successive received echo pulses appearing at the output of the detector is evaluated and utilised to control a phase shifting arrangement so as to bring the phases of the successive received echo pulses into alignment and establish coherence between the detector and the radar transmitter.