Continuous beam steering and null tracking with a fixed multiple-beam antenna array system

This paper describes how continuous null tracking of a target may be achieved with a fixed pattern multiple-beam forming network with a resulting improvement in tracking accuracy when compared to beam interpolation techniques. Continuous null tracking is accomplished by cascading a hybrid phasing matrix with a beam combining networks called a steering box. The steering box combines three elementary beams in the proper ratio to form a composite sum-and-difference beam which may be continuously steered throughout the coverage angle. The change in the sum-and-difference patterns as a function of steering angle is derived for different steering loci. It is shown how pattern asymmetry may be minimized or sidelobe fall-off rate maximized by the proper choice of a steering locus. Several physical realizations of steering boxes are discussed including the steering box employed in an experimental electronic scanning radar system.