【作者】 乔永雯；

【导师】 孙超；

【作者基本信息】 西北工业大学 ， 水声工程， 2007， 硕士

【摘要】 反潜是现代海上战争的主要任务之一。如何对日益安静型潜艇进行有效的探测，长期以来一直是水声领域的一个重要研究课题。拖曳式线列阵声纳依靠其性能上的优势，已成为目前反潜战的重要装备，而拖线阵的波束形成则在其中起到了核心作用。但是，由于拖线阵目前向大孔径方向发展的趋势以及其自身的柔性结构，使其波束形成过程中不可避免地遇到了阵形畸变、“快拍失效”、运算复杂和信号失配等问题，严重影响了声纳系统整体性能的发挥。本文针对大孔径拖线阵及其波束形成中经常遇到的上述问题进行了理论分析，并对现有的解决方案进行了系统的研究和改进。本文的主要研究内容包括： 1．研究了拖线阵的阵形估计问题，对比讨论了现有阵形估计方法的性能，使现有算法得到了系统的分析与整理，并针对一个机动状态下的大孔径拖线阵进行了自适应波束形成仿真，验证了阵形估计的重要性。 2．深入分析了快拍失效问题产生的根本原因，研究了对角加载技术、零陷展宽技术和特征空间法，对算法的稳健性进行了理论分析和仿真验证。针对拖线阵的阵形畸变，提出了一种对角加载量的确定方法；提出将零陷展宽技术与对角加载量优化技术相结合的方法，以缓解存在快速运动干扰源时自适应波束形成性能的严重降低。论文还给出了在不同输入信噪比条件下如何在特征空间法和SMI算法之间选择的准则。 3．研究了子阵自适应算法，并提出了对经典子阵自适应波束形成的改进方法—子阵波束域自适应波束形成算法。采用对各子阵波束域的输出协方差矩阵求平均的方法，消除了由于有限次快拍带来的信号相关的影响，并有效抑制了随机噪声引起的自适应响应的旁瓣起伏。论文对此方法的性能及参数选取进行了分析讨论，并将阵元域的稳健自适应算法推广到了子阵波束域中，然后针对均匀线列阵进行了仿真研究，结果表明子阵波束域稳健自适应算法保持了其对有限次快拍的稳健性能，并兼具了子阵波束域处理的优越性。更多还原

【Abstract】 Antisubmarine warfare is a crucial underpinning for future navy missions. For a long time, the problem of detecting increasingly quiet submarines has been remaining a very active research area in underwater acoustics. Towed line array sonar has become the important equipment in antisubmarine warfare by its advantage of configuration and characteristics, whereas beamforming plays an important role. However, towed array always leads to problems of shape distortion and snapshot-deficient because of flexibility and large-aperture, all of which influence the whole performance available in sonar systems. In these thesis, the problems below have been systematically analyzed and the corresponding methods to resolve also been studied. The main contents are as follows:1. Towed array shape estimation techniques are studied thoroughly. Based on theoretical analysis, the current algorithms are comprehended; the importance of shape estimation has also been verified by means of computer simulation for a dynamic long towed array.2. The reasons of snapshot-deficient are analyzed thoroughly. Three robust beamforming techniques are introduced, including diagonal loading, null broadening and eigenspace-based beamformer. In order to alleviate the performance degradation of adaptive beamfonning methods in presence of fast-moving strong interferers, a robust adaptive beamforming algorithm is presented. Null broadening technique is used to suppress interferers, and diagonal loading is employed to enhance its robustness meantime. The paper also provides the rule how to make a choice between eigenspace-based beamformer and SMI beamformer.3. A new sub-array beamspace adaptive beamforming algorithm is proposed. The correlation between source signals is equivalently increased with finite snapshots at array output. This will cause the performance degradation for existing sub-array adaptive beamforming algorithms. The new algorithm decreases the correlation between source signals by averaging the multiple-beam-output covariance matrix of each sub-array, and thereby improves the performance of adaptive beamforming. Computer simulations showed that the proposed algorithm had higher output signal-to-interference and noise ratio (SINR) with fewer snapshots. In addition to the improved SINR, the new algorithm also suppresses the noise received by array elements efficiently. The diagonal loading and eigenspace-based technique are extended into sub-array beamspace to improve robustness. Computer simulation results show that sub-array beamspace algorithm retains the super performance of its element space counterpart.更多还原