Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. Copyright © 2014, by the author(s).All rights reserved.Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, to republish, to post on servers or to redistribute to lists, requires prior specific permission. High-Q capacitive-gap transduced micromechanical resonators constructed via MEMS technology have recently taken center-stage among potential next generation timing and frequency reference devices that might satisfy present and future applications. Notably, oscillators referenced to very high Q capacitive-gap transduced MEMS resonators have already made inroads into the low-end timing market, and research devices have been reported to satisfy GSM phase noise requirements while only consuming less than 80 µW of power. Meanwhile, such devices have also posted some impressively low acceleration sensitivities, with measured sensitivity vectors less than 0.5 ppb/g. Interestingly, theory predicts that the acceleration sensitivity of these devices should be even better than this, if not for frequency instability due to electrical stiffness. Indeed, electrical stiffness is predicted to set lower limits on not only short-term stability, but longterm as well, especially when one considers frequency variations due to charging or temperature-induced geometric shifts.
Micromechanical Disk Array for Enhanced Frequency Stability Against BiasPursuant to circumventing electrical stiffness-based instability, this work introduces a more circuit design-friendly equivalent circuit model that uses negative capacitance to capture the influence of electrical stiffness on device and circuit behavior. This new circuit model reveals that capacitive-gap transduced micromechanical resonators can offer better stability against electrical-stiffness-based frequency instability when used in large mechanically-coupled arrays. Measurements confirm that a 215-MHz 50-resonator disk array achieves a 3.5× enhancement in frequency stability against dc-bias voltage variation over a stand-alone single d...