High-order medium frequency micromechanical electronic filters
Kun Wang
Nguyen, C.T.-C.
Dept. of Electr. Eng. & Comput. Sci., Michigan Univ., Ann Arbor, MI;
This paper appears in: Microelectromechanical Systems, Journal of
Publication Date: Dec 1999
Volume: 8,
Issue: 4
On page(s): 534-556
ISSN: 1057-7157
References Cited: 33
CODEN: JMIYET
INSPEC Accession Number: 6458383
Digital Object Identifier: 10.1109/84.809070
Current Version Published: 2002-08-06
Abstract
Third order, high-Q, micromechanical bandpass filters comprised of
three ratioed folded-beam resonators coupled by flexural mode springs
are demonstrated using an integrated circuit compatible, doped
polycrystalline silicon surface-micromachining technology. A complete
design procedure for multiresonator micromechanical filters is presented
and solidified via an example design. The use of quarter-wavelength
coupling beams attached to resonators at velocity-controllable locations
is shown to suppress passband distortion due to finite-mass and process
mismatch nonidealities, which become increasingly important on this
microscale. In addition, low-velocity coupling methods are shown to
greatly alleviate the lithographic resolution required to achieve a
given percent bandwidth. Ratioed folded-beam micromechanical resonators
are introduced as the key impedance transforming components that enable
the needed low-velocity coupling. Using these design techniques,
balanced three-resonator microscale mechanical filters with passband
frequencies centered around 340 kHz are demonstrated with percent
bandwidths of 0.1%, associated insertion losses as small as 0.1 dB,
20-dB shape factors as low as 1.5, and stopband rejections greater than
64 dB. Measurement and theory are rigorously compared and important
limitations, such as thermal susceptibility, the need for passband
tuning, and inadequate electromechanical coupling, are addressed
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