Phase Noise Optimization of Piezoelectric Bulk Mode MEMS Oscillators Based on Phase Feedback in Secondary Loop

This work investigates the phase noise (PN) performance optimization technique based on phase feedback scheme demonstrated by a 10MHz multiple-port piezoelectric support transducer oscillator. An additional phase-locked loop (PLL) is implemented on two distinct support transducers as a secondary loop to enable precise damping and stiffness control through force-feedback. A wide quality factor (Q) tuning range of up to 41 % (Q = 7,175 – 10,161) is attained within full force-feedback phase of 2π, thereby improving an overall PN performance by 7.1dB. Moreover, the amplitude of the feedback tuning voltage (Vi) is also a key to PN reduction, which features a 10.5dB/V improvement at 1kHz offset. This technique has proven its potential as a key architecture for future low phase noise oscillators and resonant sensors.