Feedthrough-immune frequency tracking of electrostatic MEMS resonators

This thesis introduces a novel dual-tone tracking scheme for MEMS resonators. Timing references are essential in modern technology, including communication, navigation, and daily electronics. While phase-locked loops and self-sustaining oscillators are commonly used for resonator frequency tracking, MEMS resonators introduce unique challenges, such as amplitude-frequency (A-F) effects, bias sensitivity, and feedthrough, which degrade tracking performance and stability. Inspired by the Pound-Drever-Hall (PDH) technique [1], this dual-tone tracking approach effectively mitigates these issues. By leveraging dual-tone subtraction, feedthrough is eliminated, isolating the resonator’s eigenfrequency. The scheme employs frequency conversion techniques to generate an odd-symmetric error signal centered around resonance, crossing zero precisely at the target resonance frequency. This signal is used in a feedback loop to lock a voltage-controlled oscillator (VCO) to the MEMS resonator without requiring additional reference voltage. A ∼1 MHz double-ended tuning fork (DETF) resonator was tested, demonstrating real-time frequency tracking under ambient temperature variations. The observed temperature hysteresis underscores the importance of dual-mode thermometry techniques, which utilize the resonant frequency of one mode as a temperature sensor. To address this, the proposed frequency tracking scheme is also integrated into a dual-mode temperature compensation system. Additionally, experiments conducted under low bias and drive conditions confirm the effectiveness of the feedthrough-immune approach. These findings represent a promising step toward the realization of long-term stable MEMS clocks.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Electrical & Computer Engr

Grantor

University of Illinois Urbana-Champaign

Year dc:date

2025

Author dc:creator

• Yan, Jie

Contributors dc:contributor

• Bahl, Gaurav

• MEMS resonator
• Frequency tracking
• Feed-through

Statement dc:rights

• Copyright 2025 Jie Yan

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/129591

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F129591