Analysis and Design of Circular TEn11 Filters with Offset Coupling Apertures

A new structure is proposed for circular TEn11-mode filters, characterized in particular by a simpler and cheaper construction with respect to standard structures. The novelty consists in placing the rectangular coupling apertures offset instead of symmetrical on resonator side-walls. Both analysis and design procedures have been developed for these filters, based on mode-matching technique and an original equivalent circuit respectively. Some test filters have been designed and compared with symmetrical coupling versions in terms of passband frequency behavior and spurious responses.