High-power microwave gas discharge in high-Q evanescent-mode cavity resonators and its instantaneous/long-term effects

This paper presents the first experimental and theoretical investigation of high-power RF gas discharge as applied to RF front-end filters with critical air gaps in the 10s of μm. Specifically, a strongly-coupled high-Q evanescent-mode resonant cavity is utilized as a vehicle in this study. This cavity tends to concentrate the resonant electric field in a small volume between its loading post and top wall. Both experiments conducted up to 45.3 dBm at 6.5 GHz and molecular-dynamics-based modeling suggest that, as the input power is increased, gas ionization leads to increasing gas discharge inside this volume. In addition to the measured RF data, surface analysis of the cavity post and top wall lead to the same conclusion. Besides the observed instantaneous effects on the resonator's RF performance, the impact of gas discharge in its long-term performance and potential failure is analyzed.