PGC解调光纤水听器系统低通滤波器频率特性的分析与研究

Research on the frequency characteristic of LPF in fiber-optic hydrophone system with PGC demodulation

在PGC解调光纤水听器系统中,低通滤波是一个非常重要的环节.该文从PGC解调原理和低通滤波器(LPF)输入、输出信号频谱分析入手,对低通滤波器的频率特性(幅频特性、相频特性)进行研究,结合仿真实验证明了低通滤波器锐截止特性和线性相位的必要性,并提出一种对截止频率进行优化设置的新方法,利用该方法选取截止频率,可以使PGC解调系统获得更大的动态范围.

Low-pass filtering is a very important process in fiber-optic hydrophone system with phase-generated cartier （PGC） demodulation. This paper analysed the principle of PGC demodulation and the frequency spectrum of input signal and output signal of LPF. A thorough research was made on the frequency characteristics, including amplitude-frequency characteristic and phase-frequency characteristic of LPF. With the theoretical analysis and simulation, we proved the necessity of the steep cut-off characteristic and linear phase for LPF. Meanwhile, a new method to optimize the cut-off frequency is proposed in this paper. The cut-off frequency selected with this new method can obtain a greater dynamic range for the fiber-optic hydrophone system with PGC demodulation.