Synthesis and Design of Multi-band Filters Employing Multi-mode Resonators

Rapid evolution of communication technology has driven a growing demand for multifunctional and multi-band filtering systems capable of processing a large amount of data. The cavity-based multi-band filters has become an optimum solution to cope with high power and low insertion loss requirement while maintaining a compact layout. The proposed multi-band filters employing multi-mode resonators, can achieve equivalent performance with fewer cavities, thus significantly reducing the volume and footprint when compared to traditional approaches. The coupling matrix of the multi-band filters to yield a specific response can be determined by classic single-band filter synthesis techniques and optimizations. The concept is potentially applicable to most triple-mode resonators and is demonstrated in our work using waveguide and dielectric resonators. All proposed triple-band filter designs offer high Q and allow for independent control of each frequency and coupling parameter. In the optimization process, the multi-band filters can be treated as multiple single-band filters and perform the EM / numerical optimization to each channel filter individually.