A piezo-tunable gigahertz cavity microelectromechanical resonator

Abstract

RF systems need high-frequency widely-tunable high-Q bandpass filters for channel selection filters and local oscillators. This thesis describes the design, fabrication and testing of a electromagnetic cavity resonator designed for such applications. Alternative technologies provide wide tuning or high Q, but not both, and are generally not tunable. This resonator is distinguished by its simultaneous high Q near 200 and its wide high-frequency tuning range of 2.5 GHz to 4.0 GHz, which have been experimentally demonstrated. The resonator is fabricated using standard MEMS technologies and consists of a gold-lined capacitor and toroidal inductor cavity formed by etching silicon in potassium hydroxide. Frequency tuning is performed by compressing the cavity to close the capacitor gap. Testing was done with a piezoelectric actuator for this task. The match between the modeled and measured impedance is extremely good up to and beyond 5 GHz, with less than a 1% error in magnitude and phase.