A small bandwidth microelectromechanical ring resonator-based bandpass filter

This paper presents a design of a micromechanical (MEMS) ring-resonator based bandpass filter with center frequency of 4.37 MHz and a small bandwidth of 36 kHz. Flexural-mode ring resonators have been mechanically coupled using soft mechanical spring for realizing the bandpass filtering action. Due to inherent symmetry in the ring structure, a relatively simple approach is used to access a low-velocity coupling locations as opposed to its clamped-clamped beam filter counterpart, where, a little mismatch in the position of coupling location near the anchors of clamped-clamped beam may result in a bandwidth change thereby affecting its performance. The filter structure has been designed and simulated in COMSOL finite-element platform. We also show a reduction in the amplitude of spurious mode by accentuating the filter structure in its fully-differential mode which is inherently present in the ring geometry. Moreover, effect of no. of support beams used on the filter response has been analyzed.