A low phase noise 10MHz micromechanical lamé-mode bulk oscillator operating in nonlinear region

In this paper, a 10 MHz micromechanical reference oscillator is presented by combining lamé-mode bulk resonator with Q above 200,000 and low noise off-chip interface circuitry. Benefiting from high quality factor as well as large energy storage capability of the bulk resonator, low phase noise performance has been achieved even when the resonator is operating in nonlinear region with a 4 Vp-p oscillation output. A clear sine wave output signal is observed and the oscillator shows -138 dBc/Hz noise floor and -132 dBc/Hz 1 kHz away from the carrier, which meets the cellular phase noise requirement of -130 dBc/Hz at 1 kHz offset for 13 MHz GSM reference oscillators. Such oscillator does not require any gain limiting circuitry and hence makes the implementation much simpler and less noisy.