Compact Wideband Stepped Impedance Filters with Resonant Apertures

This article describes a novel compact wideband filter topology in rectangular waveguide technology, and the related design procedure. The filter structure is based on the combined use of stepped impedance resonators (SIRs) and resonant apertures (RAs). The RAs increase the selectivity without enlarging the structure of the filter. The novel design procedure that we introduce results into a substantial improvement of the out-of-band response as well as a very compact structure. As an example, a nine-pole prototype is designed, fabricated and measured showing an excellent agreement with the predicted response.