Ku-Band Waveguide Filter with Multiple Transmission Zeros by Resonant Source to Load and Bypass Cross-Coupling

In this paper, filter set-ups with improved selectivity and out of band rejection are presented. By using bypass couplings on the one hand and dispersive source to load coupling apertures on the other hand, two cross-coupled quadruplet configurations with three and seven transmission zeros are obtained, respectively. The first configuration achieves three transmission zeros, one of which is realized by bypass coupling of two oversized cavities. Therefore, only one physical cross-coupling aperture is necessary. In the second configuration an additional source to load coupling with dispersive behaviour is added. This filter is suitable for the realization of up to seven transmission zeros by combining both effects. The prototype is manufactured at Ku-band as a proof of concept. The measurements show good agreement with the simulations. Further parameter studies are accomplished to show the versatility of the proposed filter topology.