An Analytical Approach to the Design of Multiple Mode Rectangular Cavity Waveguide Filters

The multiple mode rectangular cavity structure with square corner cuts is revisited. An attempt to predict the physical dimensions of the cavity for dual mode second-order and triple mode third-order filters is made. Analytic expressions are formed to be used in the design process. The classical triple mode cavity filter structure is altered to give a finite frequency transmission zero either in the lower or upper sideband of the center frequency. The concept is illustrated with example designs. A novel additive manufacturing technique is used to fabricate a selected filter structure. The experimental results are in agreement with the expectations.