Simplified Modal-Cancellation Approach for Substrate-Integrated-Waveguide Narrow-Band Filter Design

Current substrate-integrated-waveguide (SIW) filter design methodologies can be extremely computational and time-inefficient when a narrow-band filter is required. A new approach to designing compact, highly selective narrow-band filters based on smartly positioned obstacles is thus presented here. The proposed modal-cancellation approach is achieved by translating or eliminating undesired modes within the frequency of interest. This is performed by introducing smartly located obstacles in the maxima and nulls of the modes of interest. This approach is different from the traditional inverter technique, where a periodic number of inductive irises are coupled in a ladder configuration to implement the desired response of an nth-order filter, and significantly reduces the complexity of the resulting filter structure. Indeed, the proposed method may be used to design different filters for several frequency bands and various applications. The methodology was experimentally verified through fabricated prototypes.