A Parallel-plate-based Fishbone-Shape MEMS Tunable Capacitor with Linear Capacitance-Voltage Response

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Conventional designs for MEMS parallel-plate tunable capacitor suggest rectangular electrodes and linear structural stiffness which offer high Q-factor and quick responses; however, they have low tunability of 50% and nonlinear capacitance-voltage responses. This paper presents a novel fishbone-shape parallel-plate capacitor with high tunability and linear C-V response. The electrodes consist of a set of lateral cantilever beams of different lengths, attached to a longitudinal fixed-fixed beam resembling a fishbone. When a DC voltage is applied, the longitudinal and lateral beams undergo out-of-plane deformations changing the gap between two electrodes and the capacitance. As bias voltage increases, depending on the length and location of each beam, a local pull-in for that beam occurs at a different voltage and an insulator prevents contact between the electrodes leading to a controlled C-V response. Using ANSYS® FEM simulations, a design optimization is performed to enhance the C-V response for higher tunability and linearity. The simulation results exhibit tunability over 200%, 160% of which is highly linear. The design methodology, a combination of flexible structure and controlled displacements, presented in this paper is not limited to fishbone-shape electrodes and can be extended to different geometries to obtain higher tunability and linearity.

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Journal: TechConnect Briefs
Volume: 3, Nanotechnology 2009: Biofuels, Renewable Energy, Coatings, Fluidics and Compact Modeling
Published: May 3, 2009
Pages: 256 - 259
Industry sector: Advanced Materials & Manufacturing
Topic: Informatics, Modeling & Simulation
ISBN: 978-1-4398-1784-1