A New Rigorous Method for the Determination of Iris Dimensions in Dual-Mode Cavity Filters

A variational method based on the mode expansion is used in order to determine the accurate physical dimensions of coupling irises in dual-mode cavity filters. By considering the concept of localized and accessible modes, a series of convergence tests are carried out in order to optimize the number and nature of modes which should be included in the numerical calculations. As a consequence, the size of matrices involved and the corresponding computation time are reduced dramatically. This approach, validated by corresponding experimental data, allows us to achieve a considerable reduction of the fabrication time of this type of filter. Actually, the filter can be tuned immediately without any correction of the calculated irises.