Design of A 10-MHz low phase-noise oscillator using second-mode face shear square micromechanical resonator

A 10 MHz low-phase-noise MEMS based oscillator using a MEMS square resonator is presented in this paper. In order to examine the improvement of the phase noise of the oscillator in this design, the second-mode face shear square resonator is employed in this study. By carefully designing the exact support beam locations that minimize the anchor loss, the proposed resonator achieved very high quality factor (exceeding 700,000 with T-shaped support structure). With lager dimensions than previous fundamental mode counterparts at the same frequency (more than two times), the second-mode shows many advantages over the former, such as (1) higher quality factor Q; (2) lower motional resistance R_x (achieved 82.1 Ω with 0.25 μm in gap size). Hence, the designed oscillator based on the new resonator shows the phase noise of -156 dBc/Hz at 1 KHz offset from the carrier and -158 dBc/Hz noise floor.