Extraction of generalized scattering matrix coefficients of waveguide discontinuities using the TLM method

In this paper, a method for obtaining the generalized scattering matrix coefficients of both the propagating and evanescent modes of waveguide discontinuities is presented. The method is based on the modal expansion of field distributions obtained from Transmission Line Matrix (TLM) simulations and use of the orthogonality principle to quantify the presence of specific modes. Using this approach, the coefficients have been evaluated close to discontinuities in the presence of higher order propagating as well as evanescent modes. This simple and rigorous approach enables us to characterize a discontinuity with reduced computational effort.