Abstract
In this work, we realize low-polarization-voltage (V P ) capacitive MEMS oscillators implementing vacuum packaged 50nm-gap Lamé-mode silicon micromechanical resonators and investigate their phase noise (PN) performance. Two different oscillator configurations are studied; these are here referred to as differential-in-differential-out (DIDO) and single-in-differential-out (SIDO). Clear disparities in their respective PN profiles could be observed. The DIDO outperforms the SIDO with an improved close-to-carrier PN by more than 25dB. This 17.6MHz oscillator achieves a PN of 127dBc/Hz at 1kHz offset and 132dBc/Hz far-from-carrier PN performance, which is competitive with state-of-the-art capacitive MEMS oscillators but with lowest V P in this work. The measured PN is found to be dependent on V P for our oscillators, which is probably due to the nonlinear effects augmented by the tight electromechanical coupling. © 2013 IEEE.