Analyzing the frequency response of micromachined capacitive inertial devices by the third harmonic detection

It´s a challenge to figure out the frequency response of a capacitive MEMS device due to the large coupling noises introduced by the parasitic capacitors. We present a new method to measure the frequency response based on the third harmonic detection. Different from previous methods, the frequency of the measured signal in our method is triple as that of the exciting voltage, so there is no coupling noise from the exciting voltage through the parasitic capacitors, and a higher SNR is achieved. In this paper, the principle of this method is introduced, and the configuration of the measurement system is presented. The simulation results as well as the experimental results show that this new method works very well.