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Summary: Sensors and Actuators A 122 (2005) 317325
Electrically coupled MEMS bandpass filters
Part II. Without coupling element
Siavash Pourkamali, Farrokh Ayazi
School of Electrical and Computer Engineering, Georgia Institute of Technology,
791 Atlantic Drive, Atlanta, GA 30332-0250, USA
Received 30 April 2004; accepted 9 March 2005
Available online 3 May 2005
Abstract
This paper, the second of two parts, introduces electrostatic coupling of micromechanical resonators for implementation of high-order
narrow-bandwidth bandpass filters. The concept of electrostatic coupling of closely spaced microresonators and its electromechanical modeling
is presented. Electrostatic coupling of resonators does not require any distinct physical coupling elements. The electrostatic coupling strength
betweentheresonatorsissharplydependantontheappliedpolarizationvoltagestotheresonators.Hencethecouplingstrengthandconsequently
filter bandwidth can be tuned over a wide range after fabrication. It is shown that electrostatic coupling provides the highest degree of tunability
and design flexibility among the available microresonator coupling approaches. Low frequency single crystal silicon prototypes of second
order electrostatically coupled filters are fabricated and characterized. Filter quality factor as high as 6800 (0.015% BW) with more than one
decade of bandwidth tunability is demonstrated for a second order electrostatically coupled beam filter at center frequency of 170 kHz.
© 2005 Elsevier B.V. All rights reserved.
Keywords: Micromechanical filter; Microresonator; Electrostatic coupling; SOI; Quality factor
1. Introduction
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