中文摘要：

浅海信道条件下的水声信道是一个复杂多径信道.对于传统的声纳信号处理来说的,多径信号是一种主要的干扰源.在基于时间延迟估计技术的被动定位方法中,基本的时延估计方法是互相关法.由于信号多径结构的存在,使得在水听器接收信号的互相关函数中,存在多个与若干路径对应的相关峰.因此在进行相关峰检测时,常发生相关峰模糊问题,导致时延估计出现误差甚至错误.但在这种多径信道中,若能估计出水面、水底相对于直达路径的时间延迟,并能同时获得声速垂直剖面、海深、接收深度等声学环境参数,我们就有可能计算出辐射声源的位置及深度.为此本文提出一种基于单水听器的噪声目标被动定位方法,该方法首先从接收信号的倒谱瀑布图中跟踪和提取水面或水底路径的时延,然后结合海深、水听器深度等信息估计出目标的斜距和深度.本文从理论上分析了估计器的性能,推导了斜距偏差和斜距方差的表达式.分析表明距离估计偏差与声速垂直梯度有密切关系,距离估计方差主要受多径时延估计精度影响.本文通过仿真计算了四种负梯度（0.1s-1～0.4s-1）条件下的定位偏差,以及不同时延估计精度下的距离估计方差.为了验证本文所提定位方法的有效性,进行了海上试验验证.试验中噪声目标是一个宽带发射换能器,中心频率4kHz,带宽5kHz,发射伪随机噪声连续信号,谱级约为140dB（re：1μPa）.用一只水听器接收目标辐射噪声信号,并保存在计算机中进行后续处理.试验中用GPS同步记录发射船和接收船位置.试验结果表明本文所提方法能很好地估计出声源的距离和深度,距离结果与GPS数据能很好吻合.

英文摘要：

In shallow-water acoustic channel,multipaths caused by reflections of ocean surface and bottom are very serious.The correlated multipath returns cause unwanted peaks in the cross-correlation output of receivers.These peaks introduce performance degradation of passive localization estimator based on time-delay estimation.Multipath signal becomes the dominant interference in traditional sonar signal processing.But if surface path or bottom path to direct path time delay could be estimated from received signal,and ocean acoustic parameters such as sound speed profile（SSP） and sea depth were obtained,then it is possible to estimate source range and depth.In this paper,an effective method based on cepstrum is proposed which using a single hydrophone to separate surface or bottom multipath time-delay out from the cepstrogram of received signal.These multipath time-delays are then used to estimate source range and depth.To analyze the localization algorithm performance theoretically,slant range bias and root-mean-square error expressions are derived.It can be found from the expressions that range estimation bias and root-mean-square error are the function of surface delay,bottom delay,ocean depth,source depth and receiver depth.It is difficult to find out the relationship between range and SSP directly from the expression.To explore the SSP influence on localization algorithm,computer simulations are carried out.Four negative SSP gradient values varying from 0.1 s-1 to 0.4 s-1 are considered.From the simulation results it is shown that range bias relies strongly on SSP gradient value.At the same time,root-mean-square error of slant range is calculated statistically by Monte-Carlo simulation under different multipath time delay estimation accuracies.It can be seen that root-mean-square error of slant range is mainly influenced by multipath time delay estimation error.Sea trial was conducted to verify the effectiveness of the multipath passive localization method proposed in this paper.Acoustic target is a wide band r