Quasi-Elliptic Band-Pass Filter

The proposed work demonstrates an approach to the realization of miniaturized cross-coupled bandpass filters based on three-mode resonators. The three-mode resonators are formed by integrating two coaxial conducting elements into the side walls of a rectangular waveguide, which allows the realization of transmission null on both sides of the passband. The coaxial-waveguide coupling is adjustable with coupling screws, providing tuning flexibility. Prototype 9.9-GHz third- and sixth-order filters are presented, demonstrating miniaturization and the ability to create transmission zeros on either side of the passband. The design and performance of the developed filters are validated through electromagnetic modeling and experimental measurements. These results confirm the possibility of practical realization of compact three-dimensional RF filters based on the proposed approach.