MEMS谐振器的并联电容噪声抑制

由于谐振频率和谐振器质量呈线性关系,基于MEMS谐振器的等效机械和电路模型,可用于质量传感器应用。然而,动态模式下的MEMS谐振器具有容性传导特性,其两端口结构在电极之间会存在并联电容,扭曲其传输特性,增加整个系统的频率噪声。虽然通过改进工艺可以一定程度地降低并联电容,然而工艺的复杂度和成本会因此大大增加。针对这个问题,提出了纯电路的改进策略,使用可调电容或同等MEMS对两种方式来补偿并联电容的影响,从而降低频率噪声。实验测量结果显示补偿后频率噪声大大减少,分别从300和100 Hz降低到了100和1 Hz,大大满足了其应用精度要求。

Noise Depression for the Parallel Capacitive of MEMS Resonators

Based on the linear relationship for the resonant frequency and mass of resonators,the equivalent mechanical and electrical models for MEMS resonators can be used for the mass sen-sing application.However,the MEMS resonator used in dynamic mode has a capacitive transduction scheme.The parallel capacitance between the electrodes distorts its transmission characteristic,which increases the frequency noise of the whole system.Although the parallel capacitance can be reduced to a certain extent by improving the fabrication process,the complexity of the process and the cost will increase as well.According to this problem,an electrical strategy was presented,the effect of the parallel capacitance was compensated using the tunable capacitor or identical MEMS pair,and the frequency noise was reduced.The experimental results show that after compensation,the frequency noise is largely decreased from 300 and 100 Hz to 100 and 1Hz,respectively,thus the frequency accuracy for sensing application is improved as well.