Rejection of Interference by Coherent Optical Methods

Abstract

An electrooptical array panoramically covers a space by means of a solid beam of highly directional radiation patterns. In this type of coverage, images are simultaneously formed of all radio (acoustical) sources located in the region of coverage, including sources of active or passive noise. At high power levels,1 the passive sources may “blind” the location system; this effect is manifest in that a background of bright optical noise image makes it difficult to detect the useful signals. In order to enhance the interference supression property of the electrooptical array, it is useful to generate a beam of radiation patterns minimized in the directions toward the noise sources (up to nulls). In phased-array systems that sequentially scan a space, this task is carried out by generating the needed amplitude phase distribution in the excitation of array elements [24, 134, 135, 160–163]. Such (aperture) methods have a number of shortcomings: First, the amplitude phase distribution necessary for this purpose is defined by solving a difficult synthesis problem; second, beam steering requires the synchronized reconstruction of the amplitude phase distribution in order to keep the gaps in the same directions as before; third, it is necessary to have equipment for controlling the signal phase and amplitude in all the array elements. What is more, such methods cannot be used in systems executing parallel surveillance of the space.