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

Abstract

In this paper, a 10MHz micromechanical reference oscillator is presented by combining lamé-mode bulk resonator with Q above 200,000 and low noise offchip 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 4Vp-p oscillation output. A clear sine wave output signal is observed and the oscillator shows -138dBc/Hz noise floor and -132dBc/Hz 1kHz away from the carrier, which meets the cellular phase noise requirement of -130dBc/Hz at 1kHz offset for 13MHz GSM reference oscillators. Such oscillator does not require any gain limiting circuitry and hence makes the implementation much simpler and less noisy.

Low motional impedance distributed Lamé mode resonators for high frequency timing applications

“…For example, in the FDLR2 version of the resonators, polarization voltage up to 30 V was applied to the resonator body to characterize its motional impedance with a network analyzer (Keysight E5080A). A Q-factor loading effect was observe as the polarization voltage increase, which is usually seen for low motional impedance resonators 22 . Measurements with polarization voltage up to 5 V show an unloaded Q ~254 k, whereas a loaded Q 135 k was observed at 30 V. For the loaded Q-factor, we have the following equation 27 :…”

“…The various parameters measured for different types of resonators are highlighted in Table 1. Figure 2 shows the comparison of high f.Q product in-plane Lamé mode silicon resonators in literature 3,4,6,[16][17][18][19][20][21][22][23][24][25] with the resonators fabricated in this work. With the distributed design, the three DLRs with narrow beam width successfully demonstrated high frequencies beyond the reach of any other in-plane Lamé mode designs, while maintaining a high f.Q product close to the estimated range of Akhiezer limit for shear modes in silicon 18,26 .…”

A high-performance oscillator based on RF MEMS resonator and low-noise sustaining circuit for timing applications

“…The low phase noise benefits from ultra-low noise of the sustaining circuit and excellent performance of the MEMS resonator. The phase noise of the developed oscillators is compared with the reported MEMS oscillators [7,8,9,10]. …”