Abstract: The present invention concerns an airborne radar receiver for acquisition and tracking of a target providing two range-gates displaced during a search phase and comprising means for locking the range gates onto an echo receiver which is then tracked during a tracking phase. The receiver also comprises means for supplying a third gate accompanying the first two range gates and adjacent to the latter in the direction of the greater distances, and means for bringing all the gates back to zero when the third range gate encounters an echo the width of which is greater than a predetermined value corresponding to a target.

Abstract: A high-frequency wave, e.g. from a target reflecting transmitted radar signals, arrives with different phasing at a plurality of spaced-apart receivers or at a single receiver movable with reference to the signal source. The wave components thus received are fed directly to an array of electromechanical input transducers on the entrance side of a piezoelectric crystal, or are transmitted to respective storage elements which temporarily register information of their phasing to modulate a local oscillation delivered to these input transducers, whereby micro-acoustic vibrations are generated in the crystal with a phase relationship corresponding to that of the original wave components. The acoustic waves in the crystal converge, possibly with the aid of an internal or external focusing surface, on the exit side of the crystal to excite one of a multiplicity of mechanoelectrical output transducers producing a signal indicative of that phase relationship.