基于离散时间反馈的闭环MEMS加速度计研究

Research on closed-loop MEMS accelerometer based on discrete-time feedback

MEMS加速度计的噪声和线性指标是地震监测应用领域的关键问题,采用闭环力反馈是提高这些性能的有效途径。然而,由于对质量块不需要额外的电极来施加电静力,并且其残余位移会给闭环传递函数带来显著的非线性,从而影响该方法的有效性。因此,本文提出一种基于离散时间反馈的闭环MEMS加速度计,分时完成电容变化检测及静电力反馈,最大程度的减小了反馈信号对检测信号的馈通及耦合。利用开关电容电路中的相关双采样电路噪声消除技术,及电路参数噪声优化,可实现噪声谱密度小于0.5μg/Hz^(1/2)的微加速度计。

The noise and linearity performance of a MEMS accelerometer is a critical issue for earthquake monitor⁃ing application field.Incorporating closed⁃loop force feedback is an effective way to enhance those performances.However,additional electrode to exert the electrostatic force is typically not available and residue displacement of proof mass would introduce significant nonlinearity to the closed⁃loop transfer function,impairing the efficiency of the method.This paper proposes a closed⁃loop MEMS accelerometer based on discrete⁃time,which completes the capacitance change detection and electrostatic force feedback in time⁃sharing.Furthermore,the feedthrough and coupling of the feedback signal to the detection signal.can be minimized.Using the correlated double sampling cir⁃cuit in the switched capacitor circuit to reduce the noise in low frequency and circuit parameter noise optimization,a micro⁃accelerometer with noise spectral density less than 0.5μg/Hz^(1/2) can be realized.