Stacked Substrate Integrated Waveguide Filter with Air-Holed Cavities

This paper presents a novel filter in substrate integrated waveguide (SIW) technology, based on stacked identical rectangular cavities, where the readjustment of the resonance frequency of the cavities is performed by using air holes in the center of the cavities. The coupling between two overlapped cavities is obtained by a slot in the common metal plane. The proposed topology leads to an easier fabrication of the filter, as the metal via holes are identical and aligned for all stacked cavities. To allow the connection with input/output coplanar waveguides, the use of SIW below cutoff is adopted, thus avoiding the need of blind vias. The design, the fabrication, and the experimental testing of a three-pole filter are presented to validate the proposed solution.