2 / 2021-02-02 11:06:58

Study on Phase Demodulation Method for LDV-based Microphones

Laser Doppler Vibrometer (LDV); Phase Demodulation; I/Q demodulation; Hilbert demodulation; Interference signal.

A Laser Doppler Vibrometer (LDV)-based microphone enables the acquisition of remote speech signal by measuring small-scale vibrations around a target, which has been applied in the fields of information acquisition and national security. In remote speech detection, the interference measurement signal, however, is subject to virous noise, which makes detecting and reconstructing speech signals challenging. In order to improve the detection distance and speech quality, this paper deeply analyzed the influence of components in LDV and interference optical path on the interference signal, and established the mathematical model for it. On this basis, the accuracy and real-time performance of different phase demodulation methods were compared by conducting extensive simulations and real-world expriments. According to the comparison of experimental results, the I/Q demodulation method with higher accuracy was further improved and optimized. The research of this paper plays an important role in further improving the accuracy of the algorithm and increasing the speech detectable range.