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1、国防科学技术大学博士学位论文主动声呐海底混响信号的合成方法研究姓名：郭熙业申请学位级别：博士专业：仪器科学与技术指导教师：王跃科2010-10国防科学技术大学研究生院博士学位论文 第 i 页 摘 要 摘 要 声呐是人类感知和探索海洋的重要工具, 主动声呐往往受到混响的强烈干扰而无法正常工作。为了解决混响干扰问题，主动声呐设备必须进行抗混响设计，而设计的最终效果要通过混响测试与评估。这就迫切需要一种能够产生混响模拟信号的信号源，从而为混响背景下的主动声呐提供一种经济、灵活、可重用的测试手段。 论文以混响信号模拟源的研制为背景，开展了主动声呐海底混响信号的合成方法研究。 从信号与系统的观点看，混响
2、信号是发射声波信号作用于海洋环境的输出响应，发射声波所经历的各种变换过程构成了混响的线性系统，该系统可以等效为一个滤波器。结合以上思路，本文建立了单阵元混响信号的 FIR 信号与系统模型，模型具有明确的物理意义，反映了真实的混响物理现象，由此，验证了模型的合理性。 模型的 FIR 滤波结构为混响信号模型计算方法的实现提供了基本框架，将混响信号的产生等效为滤波运算。滤波器的阶数等于散射体的数量，大量散射体的存在，导致运算过程中需要计算大量的抽头系数，为了降低计算复杂度，本文分别提出了用于近程及远程混响信号合成的 FIR 滤波器系数的计算方法。 研究了 FIR模型中滤波器的稀疏化处理问题，形成了稀
3、疏化处理的合理性准则，推导了海底混响信号的稀疏化 FIR 模型，在不同散射体滤波器系数满足独立同分布的条件下，得到了稀疏化滤波器系数的简化计算方法，仿真实验验证了滤波器系数计算方法的有效性。两种滤波器系数计算方法为单阵元混响信号的合成提供了复杂度适中的实现方法。 在垂直阵列中，由于阵元几何位置差别，混响信号在阵元之间存在着特定的时空差异。针对垂直阵列多阵元混响信号的合成问题，分别提出了用于近程及远程垂直阵多阵元海底混响信号的合成方法。对于近程海底混响，建立了垂直阵多阵元近程混响信号合成的延时滤波模型，将混响信号的合成问题转化为延时滤波的实现问题，研究了一种实现分数倍延时的插值滤波方法，仿真试验
4、验证了方法的有效性。对于远程海底混响，证明了阵元之间海底混响信号时空相关的可分离性，在此基础上，提出了基于 AR-AR 级联模型以及 MA-AR 级联模型的统计合成方法，仿真实验结果表明统计合成方法是有效的。 关键词：主动声呐；海底混响；信号模拟源；信号合成；FIR 滤波器；单阵元；垂直阵；近程；远程 国防科学技术大学研究生院博士学位论文 第 ii 页 Abstract Abstract As an important tool for human to apperceive and explore ocean, active sonar is usually interfered by re
5、verberation so strongly that it cant work normally. In order to deal with the interference, the anti-reverberation method is applied to active sonar equipment. For testing and evaluating, a signal source which can generate simulative reverberation signal is required urgently. It can offer a kind of
6、testing approach which features economy, flexibility and repeatability. Based on the design of reverberation signal source, methods of generating active sonar seafloor reverberation are researched. As viewed from signal and system, reverberation is the system response to a transmitted acoustic wave
7、input. The reverberation linear system consists of various process of transforming the acoustic wave, so the system is equivalent to a filter. Combined with the above viewpoint, FIR signal and system model is founded to model reverberation received by a single sensor. The model, with clear physical
8、meaning, realizes the actual description of how the reverberation signal is formed, which validates rationality of the model. The FIR filter frame of model offers a basic calculation framework, which makes methods of calculating reverberation be equivalent to filter algorithm. The filter order is eq
9、ual to the number of scatterers, therefore, large numbers of tap coefficients are need to be calculated. In order to reduce the computation complexity, two different algorithms of calculating FIR filter coefficient are proposed to generate short range and long range seafloor reverberation signal res
10、pectively. The problem of how to make filter sparse is researched. Firstly, a reasonable rule of sparseness is proposed. Secondly, a seafloor reverberation signal model whose FIR filter is sparse is built. Finally, on the assumption that random variables of scatterer are independent, a simplified me
11、thod of calculating sparse filter is proposed. Two kinds of algorithms for calculating filter coefficient are validated by two simulation experiments. They offer an approach to generate seafloor reverberation received by single sensor with moderate complexity. Due to geometry location difference, th
12、ere is time-space difference among different elements in a vertical array. In order to solve the problem of generating seafloor reverberation received by multi-element in a vertical array, two kinds of algorithms for generating short rang and long rang seafloor reverberation signal received by multi
13、-element in a vertical array are proposed respectively. For generating short range seafloor reverberation, a model based on delay filter is founded. Accordingly, the generating problem is translated into a filter algorithm problem. An interpolation filter algorithm is studied to solve fractional del
14、ay problem, and validity of 国防科学技术大学研究生院博士学位论文 第 iii 页 this algorithm is validated by a simulation experiment. For generating long range seafloor reverberation, it is proved that the time correlation and the space correlation are separable. On the base of that, statistical generating algorithms base
15、d on cascade AR-AR model and cascade MA-AR model are designed to generate long range seafloor reverberation received by multi-element in a vertical array. Finally, statistical generating algorithms are validated by a simulation experiment. Key words：active sonar, seafloor reverberation, signal simulating source, signal generating, FIR filter, single sensor, vertical array, short range, long range. 国防科学技术大学研究生院博士学位论文 第 IV 页 表 目 录 表 4.1 简正波模态参数. 63 国防科学技术大学研究生院博士学位论文 第 V 页 图 目 录 图 1.1 混响形成过程示意图. 4 图 2.1 混响形成过程框图.
