时间反转法在水下波导及各向异性介质中的应用研究
文献类型：学位论文
| 作者 | 陆铭慧 |
| 学位类别 | 博士 |
| 答辩日期 | 2003 |
| 授予单位 | 中国科学院声学研究所 |
| 授予地点 | 中国科学院声学研究所 |
| 关键词 | 时间反转法 水下波导 各向异性 |
| 中文摘要 | 时间反转法不需要介质和换能器阵几何结构的先验知识就能实现自适应聚焦，因而时间反转法自从被提出以来就一直受到人们的极大关注。在复杂介质和结构中，一些声学参数往往难以得到，而时间反转法却不需要知道介质的有关参数，因此时间反转法在复杂介质和结构中是一种非常有用的方法。复杂介质和结构主要有三类：不均匀介质、波导介质和各向异性介质。对于不均匀介质，人们开展了比较多的研究工作，本文集中研究了水下波导结构和各向异性介质中的时间反转法。时间反转法在水声领域中具有很大的应用潜力，水下波导中的时间反转法研究在国际上已引起了很大关注。本文在具有硬底的均匀水层的简单波导中开展了时间反转法的理论分析和实验测量，并进行了定量的分析和对比。在单声源和声源阵列激发下，在理论和实验上证明了时间反转法能够克服由于波导多径效应导致声脉冲被展宽的波形畸变，采用时间反转法能使被展宽的脉冲重新压缩并恢复成原来的窄脉冲，而且能够获得聚焦增益，提高主副瓣比。理论上采取时域中的分析，即射线理论分析，理论分析包括：在接收点处脉冲被重新压缩的自适应聚焦过程、聚焦增益和主副瓣比、聚焦的全声场分布和焦点附近声场的横向分布和纵向分布。实验上研究了时间反转法的自适应聚焦、聚焦增益和主副瓣比以及横向分布。结果表明理论和实验基本相符。在此基础上，本文研究了水下扩频通信信号的时间反转处理，进行了相类似的理论分析和实验研究，时间反转法在水下通信中同样可以获得较大的聚焦增益和主副瓣比，从而在扩频通信中能大为降低误码率以及增加通信距离。各向异性介质中的时间反转法是我们实验室首创发展的。本文在理论和实验上证明了时间反转法同样适合于各向异性介质，可以在不知道各向异性的取向和声速各向异性分布的情况下实现自适应聚焦。理论上研究了立方晶系和六角晶系中的纵波声场，采用射线远场近似法研究了自适应聚焦、聚焦增益、全聚焦声场空间分布、焦点附近声场的横向分布和纵向分布、以及聚焦声场的时空变化全过程。实验上研究了单晶硅中纵波的自适应聚焦、聚焦增益和焦点附近的声场横向分布，实验结果基本上验证了理论分析的正确性。总之，时间反转法在水下波导（特别是水下扩频通信）和各向异性介质中可以实现自适应时空聚焦，获得聚焦增益及提高主副瓣比。 |
| 英文摘要 | Time Reversal Method (TRM) is a self-adaptive focusing method which doesn't require the priori knowledge of medium and transducer array. TRM has been paid attention to since it was proposed in acoustic research. It is difficult to obtain the medium parameters in complicated medium and structure. However, TRM doesn't require this priori knowledge. So, TRM is a useful method of self-adaptive in complicated medium. There are mainly three kinds of complicated medium and structure: inhomogeneous, waveguide and anisotropic media. Many studies have been conducted about TRM on inhomogeneous medium. So, it is focused on TRM self-adaptive focusing in underwater waveguide and anisotropic media in this paper. TRM has a great applied potentiality in underwater research. TRM in underwater waveguide has been paid attention to. TRM in fluid layer on a hard bottom is theoretically and experimentally studied in this paper, and the quantitative analyses and comparisons are obtained. It is proved by theory and experiment that TRM can overcome waveform distortion caused by multi-path effect in underwater waveguide. The waveform is usually distorted and widen when acoustic wave propagate in underwater waveguide. However, the distorted and widen waveforms can be recovered to the original narrow pulse by TRM. Good focusing gain and the ratio of major lobe to minor lobes can be obtained. The ray approximation method is adopted in theory. It is analyzed the self-adaptive focusing, focusing gain, ratio of major lobe to minor lobes, full acoustic field distribution, and the longitudinal and transversal distributions of field. In experiment, TRM focusing, focusing gain, ratio of major lobe to minor lobes, and the transversal distribution of field are also investigated. It is shown that theoretical results are coincident to experiment results. Then, underwater spread spectrum communication is studied by TRM. The similar theoretical analyses and experimental researches are carried out. It is found that TRM can be applied to underwater communication and obtain the focusing gain and the ratio of major lobe to minor lobes. TRM can decrease bit error rate and increase communication distance. TRM in anisotropy is studied firstly in. our laboratory. It is shown by theory and experiment that TRM can be applied to anisotropic medium for self-adaptive focusing without orientation of anisotropy and distribution of acoustic velocity. The compressional field in cubic and hexagonal crystal systems is studied in theory. The self-focusing, focusing gain, full acoustic field distribution, and the longitudinal and transversal distributions of field are analyzed by ray approximation method for the Silicon of cubic crystal The self-focusing, focusing gain, and the transversal distributions of focus field are also investigated in experiment and the results show the validity of theory. In a word, TRM can realize self-adaptive focusing in underwater waveguide (especially in underwater spread spectrum communication) and anisotropy and obtain good focusing gain and ratio of major lobe to minor lobes. |
| 语种 | 中文 |
| 公开日期 | 2011-05-07 |
| 页码 | 105 |
| 源URL | [http://159.226.59.140/handle/311008/1020]  |
| 专题 | 声学研究所_声学所博硕士学位论文_1981-2009博硕士学位论文 |
| 推荐引用方式 GB/T 7714 | 陆铭慧. 时间反转法在水下波导及各向异性介质中的应用研究[D]. 中国科学院声学研究所. 中国科学院声学研究所. 2003. |
入库方式： OAI收割
来源：声学研究所
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