Field theoretical computer-aided design of rectangular and circular iris coupled rectangular or circular waveguide cavity filters

The rigorous CAD of a class of rectangular and circular waveguide cavity filters which are coupled by rectangular and/or circular irises is described. The design theory is based on the full-wave mode-matching method for three key building block elements (asymmetric rectangular double-step, asymmetric rectangular-to-circular and circular-to-circular waveguide junctions) associated with the generalized S-matrix technique for composite structures. The waveguide filters may be arbitrarily composed of the key building block elements and the rectangular or circular waveguide sections between them. Finite iris thicknesses, higher-order mode interactions, and asymmetric structures are rigorously taken into account. The theory is verified by measurements.<>