A fast high-Q X-band RF-MEMS reconfigurable evanescent-mode cavity resonator

This paper presents the design, fabrication, and measurement of an X-band evanescent-mode reconfigurable RF-MEMS cavity-based resonator with a fast response (84–112 µs) and a high quality factor of 593–1,077 between 10.7–13 GHz. An array of MEMS fixed-fixed beams biased against their own substrate are used as the tuning mechanism. By designing the DC bias to be completely external to the cavity, the coupling between the DC bias-line and the RF signal is virtually eliminated. This is a key property in measuring a tunable resonator quality factor that exceeds 1,000 at 13 GHz. This paper also quantifies the quality factor reduction solely due to the MEMS tuning array spatial distribution. Specifically, compared to an ideal static 15.5 GHz evanescent-mode cavity resonator with a simulated Q = 1,750, the MEMS array diminishes the resonator quality factor by only 7.4% (simulated Q = 1,620; the measured Q value is 1,400). The measured switching times are 84 µs and 112 µs for the up-to-down and down-to-up operations, respectively. To the best of our knowledge, this is the fastest response for a tunable X-band cavity-resonator with this quality factor.