水下回波处理中分数阶傅里叶变换的带通采样实现方法

利用球形压电陶瓷自身所具有的耐压能力,采用径向极化空气背衬压电球壳换能器作为声学接收敏感元件,设计并制作了一种球形耐压水听器。首先对其低频开路接收灵敏度和谐振频率等声学特性进行了分析和有限元仿真,然后对其强度和稳定性等耐压性能进行了分析和有限元仿真,最后对其声学性能和耐压能力进行了测试。测试表明,该球形耐压水听器的直径为36 mm,工作频段为50 Hz10 kHz,低频接收灵敏度为􀀀198:4 dB(0 dB=1 V/Pa),等效自噪声谱级为46.5 dB@1 kHz,其耐压深度可达3000 m。该耐压水听器为大深度水听器设计提供了参考,在深水声学领域具有重要的应用价值。

An implementation approach of fractional Fourier transform with bandpass sampling in the underwater echoes processing

Linear frequency modulated (LFM) signal is usually been used for underwater target detection in active sonar system. Fractional Fourier transform (FrFT) method has unique advantage when processing the LFM echos to obtain effective estimations of target parameters in a low SNR or high reverberation environments. A common strategy to improve the range and velocity resolution of active sonar system is to increase time bandwidth product of the transmitted signal. Then the computation complexity of method increases dramatically, especially the FrFT-based data processing method with Nyquist sampling. As a result, the method can hardly meet the real-time requirements of unmanned underwater vehicle (UUV) with constraints on the volume and power consumption. To address the problem, we proposed an approach to implement the FrFT method with band-pass sampling. By modifying the projection of time-frequency characteristic line of LFM signal on fractional domain, correct estimations of target parameters can be obtain by using FrFT method to process echo data with band-pass sampling. The processing results of simulation data and experimental data of UUV prove the validity of the method, and the corresponding data processing time can meet the real-time requirements of UUV.