Technique and Circuit for Contactless Readout of Piezoelectric MEMS Resonator Sensors

Year: 2020

Authors: Bau M., Ferrari M., Begum H., Ali A., Lee JEY., Ferrari V.

Autors Affiliation: Univ Brescia, Dept Informat Engn, Via Branze 38, I-25123 Brescia, Italy; INO CNR, Via Branze 45, I-25123 Brescia, Italy; City Univ Hong Kong, Dept Elect Engn, Kowloon, Hong Kong, Peoples R China;‎ City Univ Hong Kong, State Key Lab Terahertz & Millimeter Waves, Kowloon, Hong Kong, Peoples R China

Abstract: A technique and electronic circuit for contactless electromagnetic interrogation of piezoelectric micro-electromechanical system (MEMS) resonator sensors are proposed. The adopted resonator is an aluminum-nitride (AlN) thin-film piezoelectric-on-silicon (TPoS) disk vibrating in radial contour mode at about 6.3 MHz. The MEMS resonator is operated in one-port configuration and it is connected to a spiral coil, forming the sensor unit. A proximate electronic interrogation unit is electromagnetically coupled through a readout coil to the sensor unit. The proposed technique exploits interleaved excitation and detection phases of the MEMS resonator. A tailored electronic circuit manages the periodic switching between the excitation phase, where it generates the excitation signal driving the readout coil, and the detection phase, where it senses the transient decaying response of the resonator by measuring through a high-impedance amplifier the voltage induced back across the readout coil. This approach advantageously ensures that the readout frequency of the MEMS resonator is first order independent of the interrogation distance between the readout and sensor coils. The reported experimental results show successful contactless readout of the MEMS resonator independently from the interrogation distance over a range of 12 mm, and the application as a resonant sensor for ambient temperature and as a resonant acoustic-load sensor to detect and track the deposition and evaporation processes of water microdroplets on the MEMS resonator surface.

Journal/Review: SENSORS

Volume: 20 (12)      Pages from: 3483-1  to: 3483-14

KeyWords: thin-film piezoelectric-on-silicon resonator; aluminum nitride; time-gated technique; contactless interrogation; piezoelectric MEMS resonator; sensors
DOI: 10.3390/s20123483

Citations: 4
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