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信号混叠是基于光纤水听器的现代声纳系统走向应用必须解决的一个关键问题。初步的实验结果已经表明,声低通滤波光纤水听器是解决信号混叠问题的一种简单且行之有效的方案。基于电声类比理论,建立了声低通滤波光纤水听器的低频集中参量模型,利用电路分析的方法对其频响特性进行了研究。结果表明,这种光纤水听器系统与典型的二阶低通滤波电路具有相似的频响特性。为了验证理论分析的正确性,设计制作了一个简单的声低通滤波光纤水听器,并在驻波罐中对其声压灵敏度频响特性进行了测试,实验结果与数值计算的结果基本吻合。该光纤水听器低频响应非常平坦,声压灵敏度约为-141 dB,测量共振频率为985 Hz,与理论值1270 Hz基本一致。共振频率处的声压灵敏度为-126.8 dB,衰减速率约为20 dB/倍频程,3000 Hz以后的灵敏度衰减幅度大于20 dB。
Signal aliasing is a key issue that must be solved in the application of modern sonar systems based on fiber hydrophone. Preliminary experimental results have shown that acoustic low-pass filter fiber hydrophone is a simple and effective solution to the signal aliasing problem. Based on the theory of electroacoustic analogy, a low-frequency lumped parameter model of acoustic low-pass filter hydrophone is established, and its frequency response characteristics are studied by means of circuit analysis. The results show that this fiber hydrophone system has the similar frequency response characteristics as the typical second-order low-pass filter. In order to verify the correctness of the theoretical analysis, a simple acoustic low-pass filter fiber hydrophone is designed and fabricated. The frequency response of the sound pressure sensitivity is tested in a standing wave tank. The experimental results are in good agreement with the numerical results . The low frequency response of the fiber hydrophone is very flat with a sound pressure sensitivity of -141 dB and a measured resonance frequency of 985 Hz, which is basically the same as the theoretical value of 1270 Hz. Sound pressure sensitivity at the resonant frequency is -126.8 dB, attenuation rate is about 20 dB / octave, sensitivity attenuation after 3000 Hz is greater than 20 dB.