A Novel Low-Pass Filter Based on Rounded Posts Designed by an Alternative Full-Wave Analysis Technique

A new low-pass waveguide filter topology is proposed based on capacitive posts using rounded shapes. The new structure is designed using a technique that benefits from a full-wave integral equation simulation tool for arbitrarily shaped capacitive microwave circuits. This integral equation method enables one to apply an efficient filter design technique employing iris geometries other than rectangular discontinuities, such as the one based on rounded posts proposed in this work. A prototype using circular posts has been manufactured and measured obtaining excellent results as compared with predictions, thus demonstrating the practical feasibility of the new proposed filtering structure. A new filter using elliptic capacitive posts was compared in terms of multipactor risk against similar filters based on traditional rectangular windows and on rectangular posts. Simulation results indicate that the new proposed concept using rounded shapes leads to geometries that can double multipactor thresholds as compared with traditional filters.