A full‐wave analysis of tuning and coupling posts in dual‐mode circular waveguide filters

A generalized scattering matrix of a circular waveguide with several posts inserted has been derived. The number of posts can be selected from one to eight and placed at 45° angles on the waveguide perimeter. Computation is based on an automated finite-element-mode-matching method that only requires the main geometrical dimensions as input data. A structure containing three screws inserted in a dualmode cylindrical cavity, iris coupled to input and output rectangular waveguides, has been analyzed. Excellent agreement with measured data has been found. © 1994 John Wiley & Sons, Inc.