A useful approximate analysis of the EM scattering by a rectangular antenna cavity containing an array of dominant mode waveguide loaded slots

Abstract

An efficient, approximate but accurate method is presented for predicting the electromagnetic plane wave scattering from a dielectric filled antenna cavity recessed in a ground plane backed by an array of slots which are loaded by dominant mode rectangular waveguides. As in the earlier companion paper [1], the scattered fields are found via a Multiple Scattering Method (MSM) based formulation whereby the antenna cavity is broken up into three isolated regions. The three junctions which define these different regions are located at the cavity opening, the cavity back wall containing the waveguide array, and the loads terminating each of the dominant mode guides of the array. In [1] the scattering matrices associated with the first two junctions, namely the open end junction and the slot array junction, are determined via a Moment Method (MM) based solution of the integral equations for the unknown aperture electric fields pertaining to each of these junctions. In the present paper, it is shown that the efficiency of the solution can be increased very significantly without sacrificing accuracy if the aperture electric fields of the array guides are found in closed form using a rapidly converging iteration scheme based on the dominant waveguide mode approximation rather than via the corresponding numerically intensive (MM) solution; furthermore, it is noted that the results are sufficiently accurate with only the initial approximation and hence no iterations appear to be necessary.