Field‐theory analysis of cross‐iris coupling in circular waveguide resonators

Dual‐mode circular waveguide filters employ cross‐iris couplings usually designed by small‐aperture approximations. This Letter presents a full‐wave method, which is able to rigorously analyze irises of any shape, thickness, and size, based on a mixed finite‐element method (FEM) and a mode‐matching technique. The accuracy of the method has been tested by comparing measured and computed data.