Analysis of circular-to-rectangular waveguide T-junction using mode-matching technique.

In the feed system for an orthogonal two-polarization antenna, a polarization diplexer is used for separating the vertical and horizontal polarizations. In this paper, the three-dimensional (3-D) electromagnetic field analysis by the mode matching method is carried out for the circular-to-rectangular waveguide T-junction used in the polarization diplexer. Its scattering matrix is theoretically derived. As mode functions inside the T-junction, the TE and TM modes in a parallel plate radial waveguide are used. Then, it becomes possible to provide the continuity conditions for the electric and magnetic tangential field components not only at the junction between the junction and the circuit waveguide, but also at the junction between the junction and the rectangular waveguide as well as on the junction wall. Also, by providing an approximate boundary condition at the junction plane between the junction and the rectangular waveguide, the scattering matrix can be formulated in the form that does not contain numerical integration. The numerical results obtained by the present analysis method agreed well with those by the three-dimensional finite-element method and the measured results. © 1998 Scripta Technica. Electron Comm Jpn Pt 2, 80(7), 37–46, 1997 [ABSTRACT FROM AUTHOR]