Field emission mitigation in X-band silicon-etched cavity resonators

An edge-smoothing technique for decreasing field emission and therefore increasing power handling in silicon-based cavity resonators is introduced for the first time in this paper. Specifically, this edge-smoothing process is performed in loaded evanescent-mode resonators by oxidizing the silicon surface before metal coating is applied. This process substantially decreases the cavity-etch-induced edge roughness particularly at the edges of the cavity-loading post where the electric field is the strongest inside the resonant cavity. Experimental results demonstrate that the presented technique results in a 2× power improvement (from 14.7 W to 29.4 W) for a high-quality (Qu = 558) demonstration-vehicle 11.15-GHz resonator with a 15-μm over-the-post air gap. In both the original and improved resonators, an abrupt 10-16 dB increase in loss is observed when gas breakdown inside the resonant cavity occurs. The simple yet effective edge-smoothing process is a critical technology advancement for cavity-based resonators since they are important building blocks in widely-tunable high-Q reconfigurable filters.