A USEFUL APPROXIMATE ANALYSIS OF THE EM SCATTERING BY A RECTANGULAR ANTENNA CAVITY CONTAINING AN ARRAY OF DOMINANT MODE WAVE-GUIDE LOADED SLOTS

An efficient, approximate but accurate method is presented for predict ing 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 e arlier companion paper [1], the scattered fields are found via a Multi ple Scattering Method (MSM) based formulation whereby the antenna cavi ty 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 termin ating each of the dominant mode guides of the array. In [1] the scatte ring 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 aper ture electric fields of the array guides are found in closed form usin g a rapidly converging iteration scheme based on the dominant waveguid e mode approximation rather than via the corresponding numerically int ensive (MM) solution; furthermore, it is noted that the results are su fficiently accurate with only the initial approximation and hence no i terations appear to be necessary.