Field-Theory Design of Circular Waveguide Dual-Mode Filters by a Combined Mode-Matching Finite Element Method

An efficiet hybrid mode-matching finite element method (MMFEM)is presented for the rigorous computer-aided design (CAD) of a comprehensive class of Microwave structures which are composed of homogeneous, waveguide elements with arbitrary cross-sections. This makes it possible to take advance of the MM method and the versatility of the FEM. To show the usefulness of the method, the rigorous design, of, circular, waveguide dual-mode filters is presented which are coupled by rectangular irises with rounded corners. The dual-mode coupling is achieved either by, 45° ridged circular waveguide sections or by asymmetrically located irises. The theory is verified by measurements.