Application of the Matched Modal Source Algorithm to the Efficient FDTD Modeling of Waveguide Components

A Matched Modal Source Boundary Condition (MMSBC) is proposed for the efficient modeling of waveguide components with the FDTD method. The formulation is based on the time domain modal expansion, that allows the wave propagation in a uniform hollow waveguide to be represented by a suitable translation operator. The proposed algorithm uses such operator to absorb the waves incoming to the source (reflected waves), while exciting the simulated structure. The scattering parameters are of easy evaluation since, for each considered waveguide mode, incident and reflected waves are available at the source reference plane. The simulation of a dielectric obstacle in rectangular waveguide and of mitered E-plane bends are proposed as application examples.