Lightweight, High-Q and High Temperature Stability Microwave Cavity Resonators Using Carbon-Fiber Reinforced Silicon-Carbide Ceramic Composite

This article for the first time presents a high-Q cavity resonator manufactured using carbon-fiber reinforced silicon carbide (SiC) ceramic composite material HB-Cesic. This composite has attractive properties of low coefficient of thermal expansion comparable to Invar, low density similar to aluminum, and high thermal conductivity. Its manufacturing process enabled by machining and joining renders useful design flexibility. A high-Q spherical resonator has been used as an example in this investigation. Two resonators, one monolithic version and the other one based on split-block structure have been experimented. The end-to-end processes from machining, assembly or joining, to high-conductivity coating for both structures, have been demonstrated. The RF performance of the resonators and their variation with temperature have been measured. A quality factor of over 10000 has been achieved for both resonators at 11.483 GHz. The measured high thermal stability of the resonator correlates very well with the prediction. This work establishes the feasibility of using HB-Cesic in microwave resonators and paves the way for further development and verification programme for more complex passive microwave devices such as filters and multiplexers for space applications.