【作者】 余赟；

【导师】 惠俊英；

【作者基本信息】 哈尔滨工程大学 ， 信号与信息处理， 2009， 硕士

【摘要】 水声物理、信号处理和海洋环境的紧密结合是声纳技术发展的必然趋势。基于声场的相干性阐述了多途信道中声聚焦与声屏蔽的基本原理,前者是增强基阵对一个局部区域内噪声源的接收响应,是一空间滤波技术,而后者是与前者相对的概念,降低基阵对某个局部区域内噪声源的接收响应称为声屏蔽,两者均可以通过虚拟时间反转镜实现。声场中的聚焦效应分为两种机理:阵的聚焦和多途信道的聚焦。理想信道中阵的时反聚焦与近场的聚焦波束形成是异曲同工的。利用声场聚焦效应提出的声图测量技术可以实现近场目标的高精度定位和测量辐射噪声源在运动平台及其附近的空间分布图(声图),后者对发展安静型技术及降噪措施效果评估有重要意义,有望应用于舰船的故障诊断,也可以指导先进的被动式鱼雷声白导系统识别目标的要害部位。虚拟时间反转镜声图测量技术可以改善信道的多途效应对声图的污染。仿真与海试研究验证了声图测量技术的可行性与实用性。海试研究表明:在高频段,舰船在近场仍可以看作单亮点点源,双体船双桨同时工作时是双亮点的,说明高频段的亮点部位对应螺旋桨。针对传统的阵处理技术无法分辨同一方向上两个点源并且声聚焦技术无法检测淹没于强干扰中的期望声源,提出了声屏蔽技术。通过将接收的信号与干扰在频域通过一个屏蔽、聚焦权滤波器,在对干扰屏蔽的同时实现对目标的聚焦,该技术可在选定的局部区域内抑制其中的声源产生的相干干扰,从而改善对屏蔽区外目标的探测性能。针对目标尺寸较大,且距离较近,即不能被简化成点源的情况,讨论了两种展宽屏蔽区的方法:矩阵拓展法和递推法,前者简单明了,后者可以减小计算量。通过计算机仿真与水池实验研究分析了影响水平阵声聚焦和声屏蔽技术实现的因素,并验证了原理的正确性,方法的可行性与实用性。更多还原

【Abstract】 One of the inevitable tendencies of sonar technology is the tight combination of physics of underwater acoustics, signal processing and ocean environment. The basic principles of the acoustic focusing and the acoustic covering, based on the coherence of the acoustic field, is proposed. The acoustic focusing is a spatial filtering technology, which enhances the array response to the local area of the targets, while the acoustic covering is an opposite concept, which reduces the array response to the local area of the noise, but both of which can be realized with time reversal mirror (TRM).There are two focusing mechanisms in the acoustic field, array focusing and multi-path focusing. Time reversal array focusing and focused beamforming can achieve the same effect, although they are different in the method. The acoustic image measurement technology utilizing focusing mechanisms can achieve high precision positioning for targets in the near field and get the distribution image of ship’s radiated noise sources, the latter is helpful for developing quiet submarine, assessment of the noise reduction effect, diagnosing the malfunction of the ship and directing the advanced passive acoustic homing torpedo to attack the vital parts of the targets. The virtual time reversal mirror technology is adopted to suppress the multi-path interference of underwater acoustic channel, which may affect the quality of the source space distribution image measurement. Simulation and sea trial researches show that the acoustic image measurement technology is feasible and valid. The sea trials researches show that the general ship can be seen single highlight in near field in the high-frequency band, but the catamaran has double highlights when its two propellers work at the same time, in other words, the radiation part of highlight in the high-frequency band is corresponding to the propeller.Acoustic covering technology in multi-path channel is proposed for the sake of distinguishing two targets in the same bearing, which is impossible for the traditional technology of hydrophone array processing, and solving the problem that the targets under the heavy interference can’t be detected only adopting the acoustic focusing technology. The signals received by every element, which contain the noise of undesirable targets and the signal transmitted by the targets in the same bearing, are weighted in the frequency domain according to their different channels, in this way, the focusing on the target and the covering to the noise can be achieved simultaneously. Coherent interference in a selected covering area can be suppressed, so the detection performance is improved to the targets outside the area. When the target is big in the size and in very near field, it can’t be modeled as point source, so two methods for broadening the covering area, matrix extending method and recursive method, are discussed. The former has a brief expression, but the computational complexity of the latter is lower.The effect factors of the acoustic focusing and the acoustic covering technology in the multi-path acoustic channel are analyzed by computer simulation and water-tank experimental researches, which also validate the technology’s correctness, feasibility and practicability.更多还原