Abstract: Coupling between non-adjacent resonators and wave propagation through the waveguide structure in distributed EM filters are reduced by forming one or more holes in one or more of the resonators (planar or folded) and by passing a conductive structure through each hole normal to the resonator. The conductive structures (vertical vias or horizontal strips) are preferably grounded, either by direct connection or capacitive coupling to one or more ground planes or by creation of a virtual ground. The holes are spaced apart from the edges of the resonator so as to minimize any interference with the current and fields concentrated at the edges of each resonator. These conductive structures narrow the effective cavity width “aeff” for the waveguide as a whole and between non-adjacent resonators without affecting the cavity width “a” between adjacent resonators.

Abstract: Coupling between non-adjacent resonators and wave propagation through the waveguide structure in distributed EM filters are reduced by forming one or more holes in one or more of the resonators (planar or folded) and by passing a conductive structure through each hole normal to the resonator. The conductive structures (vertical vias or horizontal strips) are preferably grounded, either by direct connection or capacitive coupling to one or more ground planes or by creation of a virtual ground. The holes are spaced apart from the edges of the resonator so as to minimize any interference with the current and fields concentrated at the edges of each resonator. These conductive structures narrow the effective cavity width “aeff” for the waveguide as a whole and between non-adjacent resonators without affecting the cavity width “a” between adjacent resonators.