High-Selectivity Multi-Route Bandpass Filtering Crossover Based on Substrate Integrated Pseudo-Circular Cavity

This brief presents a third-order multi-bandpass filtering crossover based on a substrate-integrated pseudo-circular cavity with coplanar components, supporting the inter-cavity coupling mechanism. The circuit is extendable to additional routes. For inter-cavity coupling, the coplanar components are employed as opposed to the conventional inductive windows method. Each route contains two pairs of parasitic non-resonant cavities. These non-resonant cavities were utilized as shots in each path to facilitate the generation of transmission zeros for each channel. The angle of placement of the coplanar coupling units between the cavities, and the parasitic coupling posts, and the dimensions of the slots in the coplanar structures influence loss control and transmission zero positions. A Six-route filtering crossover prototype with 17.5 GHz center frequency was designed and fabricated for testing. It has a high frequency selectivity advantage, with two transmission zeroes that can be controlled.