Adaptive phased-array radar processing using photorefractive crystals

An unconstrained, adaptive, null-steering phased-array optical processor that utilizes a photorefractive crystal to time-integrate the adaptive weights, and null out correlated jammers is described. A passive processor is presented, where it is assumed that it is only known a priori that the signal is broad-band and the jammers are narrow-band. The passive processor computes the angle(s) of arrival of the jammers and extinguishes them. Also presented is an active processor in which the temporal waveform of the desired signal is known, but the look direction is not. The processor computes the angle(s) of arrival of the desired signal and steers the array to look in that direction while nulling any narrow-band jammers. These are two embodiments of a class of processors which use the angular selectivity of volume holograms to form the nulls and look directions in an adaptive phased array radar antenna pattern