Phase-Noise Reduction in a CMOS-MEMS Oscillator Under Nonlinear MEMS Operation

In this paper, we will present an all-CMOS oscillator based on monolithically integrated MEMS resonators fabricated from the VIA layer (tungsten) of a 0.35 μm CMOS technology process. With this CMOS MEMS closed-loop system, the nonlinear MEMS frequency response due to the electrostatic actuation has been reconstructed. Using a phase-controlled closed-loop the frequency stability of the self-sustained oscillator at different nonlinear operation points has been analyzed, showing an optimal point belonging to the unstable region of the MEMS resonator.