Boundary integral equation approach to multi-mode Y-Matrix characterization of multi-ridged sections in circular waveguide

Aiming at an accurate and effective CAD procedure for circular waveguide (CW) dual-mode filters without tuning screws, the boundary integral equation method (BIEM) is applied to TM/TE mode analysis of Multi-Ridge circular waveguide (MRCW) and evaluation of CW-MRCW mode coupling coefficients to obtain the Multi-Mode network (Y-Matrix) representation (MMNR) of CW-MRCW transitions. A novel multiple eigenvalue search algorithm assures completeness of the modal spectrum up to large mode indices (>100) in the presence of accidental degeneracies and clusters of eigenvalues.