The reduction of radar glint by diversity techniques

Variation of the apparent angular location of a radar target, or glint, is a form of backscattered wave-interference phenomenon. The resulting error can be of such magnitude as to indicate the reflecting object to be many times the target span beyond the actual target extent. A survey of the literature dealing with glint is presented. This review reveals no analytical model which is adequate in describing glint for a complex target, and yet simple enough to permit reasonable implementation for evaluating diversity improvements. A model is developed which uses the concept of computing the total backscattered field by coherent summation of the field contributions from nonisotropic scattering complexes. The glint error is determined by use of a simple geometric construction, together with values of total field phase in the region of the tracking aperture. A technique of synthesizing nonisotropic amplitude and phase patterns for scattering complexes is described. The results, having used a synthesized target and applying frequency and space diversity in a computer analysis, are presented. These indicate considerable tracking improvement by using the simple scheme of choosing the tracking-error signal which corresponds to the diversity return having the largest signal amplitude.