Design of Zero-crossing Demodulation System for Measurement of Underwater Acoustic Pressure by Optical Method
WANG Min1,YANG Ping1,HE Long-biao1,FENG Xiu-juan1,YANG Jia-li2,ZHANG Yue1
1. National Institute of Metrology, Beijing 100029, China
2. College of Information Science & Technology, Beijing University of Chemical Technology, Beijing 100029, China
Abstract：Optical heterodyne interferometry is the mainly recommended technique for the next generation of underwater acoustic standards. The output Doppler signal of the optical interferometer should be demodulated by proper demodulation method, which will directly affect the acoustic particle velocity and pressure. To obtain the accurate reconstruction of underwater acoustic pressure by optical method, a zero-crossing demodulation method is introduced and an on-line demodulation system is designed. This system uses two orthogonal signals generated by function generator to simulate the outputs of photodiodes. A differential amplifier combines the two signals into one, which is recorded by an oscilloscope. Then the data are read and processed by a program containing the zero-crossing demodulation method to extract the acoustic particle velocity. Experiment results demonstrate the validation of the demodulation method and system. The designed zero-crossing demodulation system could be applied to the reconstruction of underwater acoustic pressure using optical heterodyne interferometry directly.
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2019, Vol. 40 
