Abstract: A monopulse radar system in which circuits are included for specific identification of echoes from helicopters vis-avis other echoes. The identification is based on either the large Doppler spectrum of a helicopter echo or the amplitude modulation thereof, or both. Embodiments are shown which utilize these criteria for identification as well as bearing refinement. The apparatus is effective, even when a helicopter is hidden from the full view of the radar by foliage.

Abstract: A high range resolution FM-CW radar system, having a range resolution cell on the order of the minimum distance between two highly reflective points of a target. Circuits are included for evaluating the difference between the echo intensity received from a resolution cell containing a highly reflective point of a target and that received from a resolution cell located at the same distance but containing only clutter.

Abstract: A radar system for transmitting pulsed circularly polarized wave, having two separate receiving channels corresponding to the two mutually orthogonal components of the received wave. Apparatus is included for detecting variations of phase between the two receiving channels and automatically adjusting amplitude and phase of at least one of the two channels in order to compensate for the depolarization effects of rain. For isolating rain return signals and bona fide target signals, the ordinary range gate of a tracking radar plus wide early and late gates are used, applicable to target and rain return signals, respectively.