On the Coupling between a Circular Corrugated Waveguide and a Pair of Rectangular Waveguides through Zero Thickness Transverse Slots Placed Diametrically at the Bottom of a Corrugation

A corrugated circular waveguide and a pair of rectangular waveguides placed in diametrically opposite positions on the circumference of corrugated circular waveguide, all of them being aligned axially, are coupled periodically through transverse slots at the bottom of corrugations. Such a structure has useful application in multimode tracking and wide band diplexing systems. In this paper, a detailed investigation of the configuration is presented. The formulation is based on the moment method solution for aperture coupling between two dissimilar regions. The admittance matrix of the configuration is set up explicitly. In setting up the terms of admittance matrix which correspond to corrugated waveguide region, firstly the influence of normal TMon modes of the radial line are determined when these modes are subject to the boundary condition given by the hybrid modes of the corrugated waveguide. These hybrid modes may be propagating or evanescent with complex propagation constant. Secondly, influence on the admittance matrix elements due to TEmn/TMmn (m ≫ 0) modes in the radial line is determined when these modes are highly evanescent. The terms in admittance matrix due to rectangular waveguide region is achieved in terms of TE/TM modes of the rectangular waveguide following the previously established procedures. The tangential fields on the coupling aperture are represented by a sinusoidal fourier set of basis functions. At the conference, the theory described in the paper will be discussed briefly, while computational merits of the formulation, the theoretical results and its co-relation with experimental results will be presented in detail.