A Geometrically Shaped Hemispherical Cavity Resonator with Extended Spurious-Free Region

This paper presents a geometry-RF-integrated design approach to eliminate spurious resonances in air-filled high-quality-factor cavity resonators. The presented approach is implemented by properly shaping the geometry of the target cavity resonator with a set of tool cavity geometries. A new class of geometrically shaped air-filled hemispherical cavity resonator is proposed and it demonstrates a high unloaded quality factor (Qu >4680) and highly reduced number of spurious resonances. The first spurious-mode frequency of the proposed resonator is nearly an octave of the fundamental-mode frequency, and compared to conventional cavity resonators the spurious-free region is significantly extended, without losing the high quality factor attribute of the resonator. The proposed geometrically shaped cavity resonator exhibits great potential in enhancing stopband performance of cavity filters.