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题名	水下畸变信道宽带信号检测技术研究
作者	周晓萌
学位类别	博士
答辩日期	2009-05-27
授予单位	中国科学院声学研究所
授予地点	声学研究所
关键词	畸变信道 宽带信号 副本相关器 多普勒扩展 时间扩展 信道相干时间 信道相干带宽 时频副本相关器 时频对偶性
其他题名	Detection Techniques for Broadband Signaling over Underwater Dispersive Channels
学位专业	信号与信息处理
中文摘要	随着实际应用需求的转变及相关基础科学理论的发展，水声信号处理正朝着浅海环境下宽带主动声纳信号处理的方向发展。在研究主动声纳宽带信号检测问题时，水声信道的时、空变化特性对宽带信号检测性能的影响是不容忽视的，信道的多途传播将引起回波的时间扩展，信道的快速起伏将引起回波的多普勒扩展。本论文结合实验室承担的项目任务，主要研究频率扩展信道、时间扩展信道和时间频率双扩展信道三种畸变信道下的宽带信号检测问题，重点讨论当各种畸变信道的扩展特性未知时，如何有效地解决各种检测算法的失配问题，提高检测器的稳健性；以及针对时间频率双扩展信道，如何对信道建模并实现有效检测。本论文的基本内容和主要创新点如以下几个方面： （1）研究了宽带信号的特点，阐述了宽带信号处理的基础理论，包括宽带目标回波的模型、宽带相关处理和宽带模糊度函数等方面；讨论了水声信道的二阶统计特性，定义了表述信道传输特性的若干参数，并根据这些参数对信道进行分类；分析了理想信道的最佳似然比检测器为副本相关器，并分析了其检测性能。 （2）针对频率扩展信道，研究了其最佳似然比检测器SRC（Segmented Replica Correlator）的检测性能，并用数值仿真进行验证。提出了多重假设SRC检测算法，解决了频率扩展信道的相干时间未知时SRC失配的问题。该算法提高了SRC的稳健性，并能简单快速地估计信道的相干时间。 （3）针对时间扩展信道，分析了此种畸变信道的起因，研究了其最佳似然比检测器RCI（Replica Correlation Integration）的检测性能；提出了一种基于Page Test 的序列检测算法，该算法将时间扩展信道下的回波信号建模为一个双边变化的过程，不需要信道扩展时间的先验知识，就能实现有效检测，另辟其径，解决了RCI的失配问题。 （4）针对时间频率双扩展信道，建立了抽头延迟线模型和信道网格模型。在双扩展信道网格模型的基础上，提出了一种基于短时傅立叶变换的时频副本相关器（Time-Frequency Replica Correlation ，简称TFRC），该算法是针对双扩展信道的宽带时频处理框架，具有能很好地匹配信道的时变特性并充分利用宽带信号的优点，数值仿真表明RCI和SRC都是TFRC的特例，并验证了TFRC的有效性。 （5）将网络通信领域的时频对偶理论（Time-Frequency Duality）运用到畸变信道回波检测问题中，研究了各种畸变信道的关系。当发射信号是具有平滑相位函数的调频信号时，时间扩展信道与频率扩展信道对回波的影响是等价的，满足时频对偶理论，因此，两种不同畸变信道的检测方法可相互借鉴。
英文摘要	With the requirements of the practical application and the development of basic scientific theories, acoustic signal processing is directing in shallow water environment of broadband signal processing. In active sonar, broadband signal distortion produced by the channel dynamics makes signal reception and detection particularly challenging. The signal is distorted in delay-spread over multiple propagation channels. Meanwhile, the signal encounters Doppler-spread over fast fading channels. In this dissertation, detection techniques for broadband signaling over Doppler-spread channel,delay-spread channel and doubly-spread channel are addressed respectively. Specifically, some new methods are investigated to combat mismatch and improve the receiver performance when the distortion characteristics of the channel are unknown. Furthermore, methods for modeling doubly-spread channels and designing time-frequency framework over doubly dispersive channels are proposed. The basic content of this dissertation and main points of innovation are as follows: (1) The basic broadband signal processing theory is addressed. And also, channel characteristics and the classification for the dispersive channels are discussed. (2) For unknown coherence time Doppler-spread channels, a multihypothesis segmented replica correlator(SRC) is proposed to improve the robustness of the SRC and estimates quickly the coherence time of the channel. (3) For delay-spread channels, the optimal likelihood ratio test detector is replica correlator intergration(RCI).When the spread time and accurate knowledge of the channel are unknown,the performance of RCI will be significantly degraded. A sequential detector based on Page Test is proposed for the detection of delay-spread active sonar echoes.The detector also provides estimation of the starting and stopping times of the received echoes. (4) For doubly-spread channels,a tapped-delay line model is addressed and a time-frequency replica correlator (TFRC) detector based on short-time Fourier transform is introduced. This detector optimally matches to the characteristics of the doubly-spread channel and fully exploits the advantage of broadband signal. Numerical simulations show that the RCI and SRC are the special cases of TFRC which verify the validity of the TFRC. (5) Using the time-frequency duality theory, the relationship among various distortion channels is investigated. Results show that the performance of the SRC detector in a delay-spread channel approaches the performance of RCI detector when the transmitted signals are FM signals with smooth phase functions,and similarly,the performance of the RCI detector in a Doppler-spread channel approaches that of the SRC detector in this case.
语种	中文
公开日期	2011-05-07
页码	120
内容类型	学位论文
源URL	[http://159.226.59.140/handle/311008/488]
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	周晓萌. 水下畸变信道宽带信号检测技术研究[D]. 声学研究所. 中国科学院声学研究所. 2009.

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