MEMS石英振梁高增益谐振电路的设计与分析

Design and Analysis of High Gain Resonant Circuit of MEMS Quartz Vibrating Beam

介绍了一种基于新型高阻抗QVBA的高增益谐振电路设计和谐振电路的分析测试实验。利用阻抗分析仪4294A测得石英振梁的等效参数,对石英振梁的电气特性进行分析,发现高阻抗石英振梁起振比普通晶振需要更高增益。基于双门振荡电路,利用运算放大器在开环系统中具有无限增益的理论,提高谐振电路的驱动能力。同时采用谐波抑制网络,指出谐波抑制网络可以抑制无用的频率避免传感器输出信号出现泛音频率,并提高谐振电路的稳频速度。考虑电噪声对输出波形质量的影响,在电路的输入部分采用滤波电容,并在电路的输出部分采用反向器整形,使电路输出标准的方波信号。最后利用安捷伦DSO5012A型号示波器和频率计对高增益谐振电路和石英振梁组成的谐振系统进行测试,测试结果表明本文设计的谐振电路与石英振梁组成的谐振系统可以输出标准的方波信号,输出频率精度达到10-5 kHz,在振动稳定以后频率变化小于0.1 Hz,无泛音频率出现,对研究高精度MEMS加速度计传感器具有重要意义。

This paper introduces the design of a high gain resonant circuit based on a new type of high impedance QVBA and the analysis and test of the resonant circuit.The equivalent parameters of quartz vibrating beam are measured by impedance analyzer 4294A,and the electrical characteristics of quartz vibrating beam are analyzed.It is found that high impedance quartz vibrating beam needs higher gain than ordinary crystal vibration.Based on the theory that the operational amplifier has infinite gain in the open-loop system,the driving ability of the resonant circuit is improved.At the same time,it is pointed out that the harmonic suppression network can suppress the useless frequency,avoid overtone frequency of the output signal of the sensor,and improve the frequency stabilization speed of the resonant circuit.Considering the influence of electric noise on the quality of output waveform,the filter capacitor is used in the input part of the circuit,and the inverter is used in the output part of the circuit to make the circuit output standard square wave signal.Finally,using Agilent DSO5012A oscilloscope and frequency meter to test the resonance system composed of high gain exciting circuit and quartz vibrating beam.The test results show that the resonance system composed of exciting circuit and quartz vibrating beam designed in this paper can output standard square wave signal,the output frequency accuracy reach 10-5 kHz,and the frequency change is less than 0.1 Hz after the vibration is stable.There is no overtone frequency,which is of great significance to the research of high-precision MEMS accelerometer sensor.