基于同态滤波的浅海水声定位多途抑制技术研究

Underwater acoustic localization and navigation have great significance in both military and civilian domains.The complex and changeable multi-path channel is one of the main factors that influence the accuracy and reliability of shallow water acoustic positioning system.Aiming at developing the anti-multi-path technique for shallow water rapidly time-varying channel and improving the capability of the underwater cooperative targets localization system, the features of shallow water multi-path channel and its influence mechanism on the acoustic positioning are researched. Focusing on the characteristics of complex cepstrums of typical shallow water channel and acoustic pulse signals as well as the differences between them,a new method for separating them on the basis of homomorphic filter is proposed,in order to improve the detecting capability and time delay estimation accuracy of acoustic pulse signals. In addition, according to the separation conditions revealed based on the method above, the signal waveform of cooperative acoustic beacon is designed and the simulation platform for anti-multi-path ability forecast is set up.The research is expected to provide an effective way to solve the impact of the rapidly time-varying channel in real time. Therefore, the research is not only significant in improving the positioning accuracy of underwater mobile targets, but also have some theoretical value and promising prospect in other areas,such as underwater communications,underwater acoustic detection and targets recognition.

水声定位与导航在军事和民用领域均有重要意义。浅海水声定位中，复杂多变的信道多途是影响系统定位精度及可靠性的主要因素之一。本项目以发展浅海快变信道多途抑制技术，提高水下合作目标综合定位能力为目标，探索浅海信道多途特征及对水声定位的影响机理，针对浅海典型信道/声脉冲信号的倒谱特征以及二者之间的差异，研究基于同态滤波思想的信道与信号分离方法，提高声脉冲信号检测能力和时延估计精度，并揭示和界定基于该方法的可分离条件，据此指导定位系统合作声信标脉冲波形设计，建立系统抗多途能力预报仿真平台。本项研究可为解决快变信道下实时抑制信道影响问题探索一条有效途径，其研究成果不仅对提高水下机动目标定位系统的定位精度和复杂水声环境适应能力有重要意义，在水下通信、水声探测和目标识别等其他领域也具有一定的理论价值和应用前景。

本课题围绕浅海水声定位中的多途抑制问题展开研究，主要研究进展及成果包括：.1.基于射线声学理论，建立了基于平整界面和分层海洋介质假设的浅海水下声信道声场模型，研究了浅海矢量声场的干涉结构，探讨了浅海信道多途冲激响应特征及规律，分析了典型多途信道下“相消干涉”等时域叠加信号的特征，揭示了多途效应对系统定位精度的影响机理。.2.推导了水下声信道冲激响应复倒谱变换表达式，分析了典型浅海水文条件下声信道和典型声脉冲信号的复倒谱特征。.3. 基于同态滤波理论，提出了两种新的信号和信道分离方法——基于尖峰搜索的复倒谱域特征滤波器构建方法和基于双基元复倒谱域重置技术的直达声提纯方法。仿真分析和试验数据处理结果表明，本课题提出的方法可有效抑制信道多途，具有构建方法简易、重构误差小等特点。.4.以重构信号与发射信号的相关性作为标准，研究了同态滤波思想下的信号和信道可分离（适配）条件，并建立了水声定位系统抗多途能力预报仿真平台。该平台可综合考虑信号波形、声速分布、收发距离等方面的因素，对不同空间位置处的抗多途性能进行评估。.5.将本课题研究成果应用到新研的长基线水声定位系统中，其中抗多途能力预报仿真平台用于指导该系统合作声信标的波形设计，以保证系统精度和稳定性；基于尖峰搜索的复倒谱域特征滤波器构建方法用于各声学分系统的信号处理中，以实现快变水声多途的实时抑制。该系统的湖试结果验证了本课题研究成果的可行性和有效性。.本课题研究成果不仅对提高水下定位系统的精度和稳定性有重要意义，在水下通信、水声探测和目标识别等领域也具有理论价值和应用前景。