Closed-Loop Mutual Compensation of Nonlinearities in MEMS Resonators

The research proposes a new technique for automatic, closed-loop, mutual compensation of hardening and softening nonlinearities in microelectromechanical system (MEMS) resonators. The technique exploits the change in sign of the frequency-amplitude relationship of resonators when passing from hardening to softening: by applying a small modulation to the displacement amplitude, and observing the frequency changes, it is possible to trigger a feedback mechanism which keeps the resonator in its linear condition for, in principle, unboundedly large amplitudes. The method is verified on a 37-kHz device with 104 quality factor (Q), showing linear operation beyond 500 nm for a 2.2 µm gap. This is about 5 times the critical displacement in absence of nonlinearity nulling, and yields a 5-fold improvement in frequency noise floor.[2025-0219]