A Finite Element Method (FEM) is presented to determine reflection and transmission coefficients of rectangular waveguide junction discontinuities. An H-plane discontinuity, an E-plane ridge discontinuity, and a step discontinuity in a concentric rectangular waveguide junction are analyzed using the FEM procedure. Also, reflection and transmission coefficients due to presence of a gap between two sections of a rectangular waveguide are determined using the FEM. The numerical results obtained by the present method are in excellent agreement with the earlier published results. The numerical results obtained by the FEM are compared with the numerical results obtained using the Mode Matching Method (MMM) and also with the measured data. Deshpande, Manohar D. Langley Research Center NAS1-19341; RTOP 522-33-11-02...

Transitions from rectangular waveguide to layered ridge dielectric waveguide are studied both experimentally and theoretically. In addition, a design procedure is given for each transition. The analysis and design procedures are valid for transitions between rectangular waveguide and other open dielectric waveguides such as Image Guide, Insulated Image Guide, Dielectric Ridge Guide, and Inverted Strip Dielectric Waveguide. It is shown that for small dielectric waveguides such as a Layered Ridge Dielectric Waveguide, a transition which is comprised of a tapered ridge waveguide reduces the radiation loss by at least 1 dB.