A 145MHz low phase-noise capacitive silicon micromechanical oscillator

This paper reports on the implementation and characterization of a low phase-noise oscillator based on a very high quality factor (Q) 145MHz capacitive silicon micromechanical resonator. The utilized resonator is a silicon bulk acoustic resonator (SiBAR) operating in its first width-extensional mode with a maximum Q
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~74,000 that is specifically optimized for low motional impedance. The sustaining circuitry is a 3.6mW CMOS transimpedance amplifier (TIA) that uses common source topology with local shunt-shunt feedback. The measured phase-noise of the oscillator at 1kHz offset from the carrier is -111dBc/Hz with phase-noise floor reaching below -133dBc/Hz.