Advances on Size Reduction and Spurious Suppression in Rectangular Waveguide Filters

In this presentation we describe a practical and systematic procedure to design a new topology for wideband waveguide filters. The novel topology that we propose is obtained by replacing the conventional <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\lambda_{g} / 2$</tex> resonators and inductive inverters, with resonant apertures (RAs) as resonators, and capacitive irises as inverters, respectively. The combined use of RAs and capacitive irises enables an efficient suppression of all spurious responses in the entire WR-75 waveguide operational frequency band, while, at the same time, significantly reducing the size of the filter. In addition to theory, a fifth-order prototype is designed, manufactured and measured. The measured response of the filter shows a high degree of correlation with both the in-band and out-of-band simulated responses, thereby fully validating both the novel topology and the design procedure.