Piezoelectric-Based Support Transducer Design to Enable High-Performance Bulk Mode Resonators

Abstract

An innovative topology to realize high-performance bulk mode devices made up of low-defect material by driving them into resonance using piezoelectric thin-film transduction is proposed and implemented in this paper. Here, the piezoelectric transducer is uniquely positioned at the bulk mode's support location. To realize the resonators, MEMSCAP Inc.'s PiezoMUMPS platform was utilized. Wine-glass and Lamé bulk mode devices are demonstrated to establish the feasibility of the support transducer drive/sense mechanism. Several drive/sense combinations of the balanced-unbalanced setup were measured. For the differential-in differential-out configuration, reduced feedthrough and enhanced stop-band rejection was observed. As a result, the Wine-glass and Lamé mode resonators having a resonance frequency ( f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> ) of 20.943 and 21.15 MHz with a motional resistance (R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> ) of 1.68 and 3.88 kQ and a loaded quality factor (Q <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">l</sub> ) of 9940 and 6840, respectively, operating in vacuum at 0-dBm driving power are demonstrated. Temperature Coefficient of Frequency of -26.4 and -25 ppm/K is recorded for Wineglass and Lamé mode resonators, respectively. To characterize the closed-loop response of the devices, they were connected to a lock-in amplifier with phase-locked loop, and a phase noise of -122 and -118 dBc/Hz at 1-kHz offset were measured for Wine-glass and Lamé mode resonators, respectively. [2018-0092]