SINOPSIS

The antenna of a multi-pozitional coherent radar system (MPCRS) is considered as a super-large-aperture very sparse phased array. Antenna modules situated at separate positions are its elements. The modules aperture has sufficiently small dimensions, and a forced focusing of the modules is permissible such that the atmosphere turbulence influence can be neglected. Accordingly, the pattern of an antenna module turns out to be so much wide that several (or group) targets or an extended target with resolvable elements fall within the range of the pattern. Therefore, the overall MPCRS antenna focusing has to be done as to such a group or extended target. If the group target is initially illuminated by a wide beam (e.g. the antenna module beam), the reflected wave received by the overall antenna, the complex conjugate field formed and radiated in the backward direction, then as many narrow beams will be formed for the transmission as the targets were radiated. Essentially, the overall antenna will prove to be focused, but the energy will be splitted up, but d it is not always acceptable. Furthermore, an individual point object (target) is required for the overall antenna focusing for the reception. And so a problem arises, to form one beam for transmission and reception when the initial illumination of the observed group of targets is made by a wide beam.
The known Waters [1] antenna self-focusing method for transmission, when many targets (or an extended target) are illuminated with a wide beam, envisages the formation of one beam for transmission after multiple reception and complex conjugate field reradiation [1]. However, one of the targets of the group being illuminated is presumed to have an effective scattering area (ESA) that differs from other targets ESA. In actual practice, natural and man-made situations can arise in which the group (elements of extended target) under observation have the same ESAs. For instance, stabilized targets such as blunt-nose cone or spherical cone moving along parallel trajectories in radial direction relative to the radar can have practically the same ESAs. A group of targets can be camuflated by inflatable spheres having metalized coating. Special multielement defocusing targets can also be created consisting of metalized inflatable spheres connected by halyards. Extended targets can contain, at certain instants of time, two or more elements having the same ESA etc. Waters method as it was published is unreliable for military-purpose radars. In this connection a practical necessity arises to extend its possibilities to cover the general case where the ESAs of a group of targets or extended-target elements turn out to be the same. Let us consider the general case where one narrow beam for transmission is formed when a group of targets (target element) having rigorously equal ESAs is initially illuminated by a wide beam.