Electrostatically coupled micromechanical beam filters

This paper presents a new electrical coupling technique for implementation of high-order narrow-bandwidth programmable bandpass filters using micromechanical resonators. The concept of electrostatic coupling of closely-spaced microresonators for filter synthesis is introduced and its electromechanical modeling is presented. The electrostatic coupling approach eliminates the need for any physical coupling element in between the resonators and provides the highest degree of tunability and design flexibility among the available filter synthesis approaches. Low frequency single crystal silicon prototypes of second order electrostatically coupled filters have been successfully implemented and characterized. Filter quality factors as high as 6,800 (0.015%BW) with more than one decade of bandwidth tunability are demonstrated in a second order electrostatically coupled beam filter with a center frequency of 170 kHz.