Dynamically Balanced Folded-Beam Suspensions for Resonators

The standard folded-beam suspension is often used in electrostatic comb-drive resonators with the intention of achieving a system with a linear response. However, we show that the harmonic response of the standard folded-beam suspension is not linear at the fundamental resonance frequency of the system. Specifically, we show that at the fundamental resonance frequency, the stiffness of the suspension increases monotonically with increasing motion amplitude. We show that even though the suspension is intended to respond as a linear spring, it is actually designed to do so only in static loading. We present a solution to the problem in the form of a new dynamically balanced folded-beam suspension. This suspension is designed such that at the fundamental frequency of the system, its response is linear, and its stiffness is unaffected by motion. The methodology for designing this suspension is fully detailed. We experimentally demonstrate the viability of the new design.