Mode Filters for Oversized Rectangular Waveguides: A Modal Approach

A semi-analytical approach, relying on the mode-matching method and the resonator technique, is proposed. It is conceived to evaluate the performance of mode filters, based on corrugations partially filled with an absorbing material, in the case of oversized rectangular waveguides. The mathematical formulation allows an accurate and fast computation of the scattering parameters, through closed-form expression of the surface integrals and some matrix algebra. The theoretical model is implemented in a code that is benchmarked against a finite-element method to elucidate its advantages with respect to volumetric solvers. After giving an insight on the physical mechanisms ruling the performance of these devices, the modal method is used to run the particle swarm optimization algorithm for different types of devices, taking advantage of the reduced computation time of the developed tool.