Generalized modal scattering matrix of discontinuity-distorted waveguide multiport junctions

A generalized modal scattering matrix formulation is presented for the calculation of discontinuity-distorted waveguide multiport junctions. Unlike common approaches based on three-plane mode-matching techniques, and modifications thereof, which calculate only the fundamental-mode scattering matrix, this algorithm computes the generalized modal scattering matrix of the junction. Therefore, the method allows the computation of components in which other structures are connected as closely as possible to the discontinuity-distorted junction as follows directly from the rigorous incorporation of all higher-order mode interactions. The method is demonstrated at three selected examples: the waveguide corner, the T-junction power divider and the orthomode transducer. Comparison with results obtained by other numerical techniques or measurements available from the literature are found to be in good agreement.