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针对MEMS器件研制中微弱信号的检测问题,提出了一种适用于电容式MEMS器件的微弱电容检测电路.此电路采用峰值检测技术,原理及结构简单;只检测待测电容的变化量,既可用于差分式检测,也可应用于单一待测电容的情况.首先利用正弦载波信号和微分电路对电容量进行载波调制,再通过减法电路得到幅值与电容变化量成比例的正弦信号,最后采用峰值检测方法解调信号,得到直流量输出.利用微小可调电容进行标定,结果表明检测电路的线性度良好,灵敏度约为3.631V/pF,精度达到0.2%.利用该检测电路检测MEMS陀螺上振动频率为2.85kHz的梳齿驱动器的电容量变化,输出信号频率为(2.85±0.02)kHz,误差低于0.7%,说明该电路能够应用于MEMS器件的微弱电容检测.
Aiming at the detection of weak signals in the development of MEMS devices, a weak capacitance detection circuit suitable for capacitive MEMS devices is proposed. This circuit uses peak detection technology with simple principle and simple structure. It only detects the variation of measured capacitance, Differential detection can also be applied to a single case of the capacitance to be measured.Firstly, the carrier wave is modulated by the carrier signal and differential circuit of the sine wave, and then the sinusoidal signal whose amplitude is proportional to the variation of the capacitance is obtained by the subtraction circuit. Finally, Peak detection method to demodulate the signal to obtain a direct current output.Using a small adjustable capacitance calibration, the results show that the detection circuit of good linearity, the sensitivity of about 3.631V / pF, accuracy of 0.2%. The detection circuit using MEMS gyro The capacitance change of the comb drive with the vibration frequency of 2.85kHz, the frequency of the output signal is (2.85 ± 0.02) kHz, the error is lower than 0.7%, which shows that the circuit can be applied to the weak capacitive detection of MEMS devices.