【作者】 马琳；

【导师】 张中兆；

【作者基本信息】 哈尔滨工业大学 ， 信息与通信工程， 2009， 博士

【摘要】 穿墙定位能够实现外部非入侵式的探测,从而满足人们对建筑物或障碍物后目标位置确定的需求,它应该是一种携带方便、能够快速准确的提供定位信息的系统。目前穿墙定位主要使用坐标定位和图像定位两种方法,前者所得结果简单明了,后者所得信息具体直观。此外,由于IR-UWB信号具有优良的穿透特性,其简单的收发信机结构使得该信号在穿墙定位研究中具有一定的优势,因而本文以IR-UWB信号为载体对二维区域内固定目标点的穿墙定位进行了全面深入的研究。由于穿墙定位系统主要应用在突发应急、灾害救援等场合,所以如何方便、快速、准确地的确定目标位置是值得关注的问题。在此要求下,本文对穿墙定位进行了较为系统的研究。基于国内外研究现状的分析指出了传统的坐标定位系统和图像生成系统由于各自的应用背景和技术特点在穿墙定位应用中存在问题与不足。本文的研究旨在解决这些问题完善这些不足,在满足穿墙定位应用的要求的前提下,从一定程度上改善基于IR-UWB穿墙定位系统的定位方法。研究内容主要包括以下几个方面:第一,对现有穿墙定位系统关键技术的研究。分析了用于定位系统的信号模型及信号处理方法。通过仿真和对比着重分析了三边测量法和反投影算法。对三边测量定位技术做了深入的分析,指出传统定位方法的优点及其无法解决穿墙定位系统对多目标点定位的问题所在。从理论上分析了锚节点阵列的图像生成方法在穿墙定位中应用中有局限性的原因,提出了反投影算法中伪影产生的本质,并得到了影响成像质量的具体参数。第二,对穿墙定位坐标定位系统的研究。针对穿墙定位系统在多目标点定位时采用传统三边定位方法导致各个接收锚节点无法区分各个目标点的反射脉冲回波信号从而无法获得正确坐标定位信息的问题,提出了一种利用IR-UWB信号先定位后校验的两步定位法。根据定位模型中配备发射机的锚节点的类型不同,将两步定位法分为TCA和TLA两种方式。在分析了如何进行参数设置以实现定位锚节点所接收到回波信号的全匹配对应的基础上,全面讨论了TOA估计与目标点数量失配情况的成因,并进一步研究了两步定位法对IR-UWB定位系统的定位精度的影响,提出了一种区域交叉定位模型以减小目标点所在区域定位精度抖动的方法。第三,对穿墙定位图像生成系统的研究。本文针对反投影算法在图像空间对每个像素点进行累加时,不仅使目标点所对应的像素点的幅度得到加强,同时也提高了其周围像素点的幅度,从而引起生成图像模糊无法分辨的现象提出了基于两步定位法的多目标点提取方法,根据定位锚节点所接收到的反射脉冲回波信号对目标点先进行坐标定位,然后通过目标点提取函数对重建图像中目标点所对应的像素点进行加权,从而有效的滤除伪影获得了高质量的生成图像。此外,在分析了回波信号与反投影的关系之后,提出了一种简单的包络近似方法,并据此确定了目标提取函数。第四,对因墙体阻挡而产生问题的研究。前文的分析都是基于自由空间的假设,本章分别从坐标定位和图像生成的角度对墙体的存在所产生的影响进行深入的分析。墙体的存在不仅改变信号的传播路径、速度以及双程传播时间,还会对目标点反射的回波信号造成极大的衰减,为了满足在有直达波干扰和信道严重衰落的条件下从较强的噪声背景下提取较弱的目标点反射脉冲回波信号,本文提出了一种基于相关处理的多帧联合检测方法来提高接收信号的信噪比从而提高了目标点的检测概率。按照墙体厚度及介电常数是否已知这两个角度研究了墙体对生成图像的影响,提出了修正反投影法的两种策略,通过对墙体参数估计误差所引起的双程时间估计误差的分析提出了通过对定位图像使用迭代方法来逼近目标点真实位置的方法。更多还原

【Abstract】 Through-wall localization can realize an exterior detection without inbreak satisfying the requirements of person or object localization behind the building wall or fraise. It should be a portable system, which is able to rapidly provide the localization and imaging information. Currently, coordinate localization and image localization are mainly adopted; result of former one is brief and simple, while the image formation information is detailed and intuitionstic. Moreover, merits like excellent penetrating characteristics and simple Tx/Rx configuration make IR-UWB advantage in through-wall localization system. Therefore, this paper mainly focused on 2D TWL on targets with IR-UWB as signal carrier.Since through-wall localization system can be adopted in some emergent occasions, much attention has been given to how to display the targets conveniently, rapidly and exactly. With such background, this paper took a relatively systemic research on through-wall localization. The problems and shortcomings of conventional localization system and imaging system in through-wall localization has been pointed out according to their applications and technique characteristic based on analysis of researching status quo inside and outside. The main purpose of this paper is to improve these issues to satisfy the requirement of through-wall localization applications and also to perfect the localization approaches on the basis of IR-UWB through-wall localization system in a certain extent. The work content includes four parts as follows:1. Investigation in key technique of through-wall localization system in existence. Signal model and processing method for localization system has been analyzed. After a deep analysis on trilateration, it points out that why conventional localization method can not solve multi targets localization in through-wall localization. By theoretic analysis, this paper explained anchor array processing for imaging technique in through-wall localization, as well as revealing essence and reason of artifact generating in back projection algorithm, so as to obtain the detailed parameter, which has an impact on imaging quality.2. Research on through-wall coordinate localization system. Aimed at the case that through-wall localization system based on conventional trilateration can hardly distinguish echo impulse signals received by each anchor node when there are multi targets in localization area so as to fail to obtain correct coordinate information, this paper presented a two-step localization method based on by first localization then checkout to solve the problem, which includes two mode as TCA and TLA. After analyzing how to settle parameters to realize echo signals full matching, this paper held a complete discuss on TOA estimation and reasons of targets number mismatching. Deeper research on impact of two-step localization approach on IR-UWB system localization accuracy make a cross-region localization method been proposed. What is more, after analyzing relationships between echo signals and back projections, this paper presented a simple envelope approximate method to fix on targets extraction function.3. Study on through-wall image formation system. An imaging localization method to wipe off artifact has been proposed to improve the imaging quality. Artifact is derived from back projection algorithm which may obtain original data in limited space for it is restricted by size of system. By target location information, the method presented in this paper solve the artifact phenomenon efficiently caused by limited anchor array length, which improve the targets distinguished ability more effectively compared with other ways.4. Work on problems in wall obstructing. Since analyses above are on the assumption of free space, a multi frames detection method is proposed based on spread frequency technique to extract weak signal under direct wave interference in serious attenuating channel in order to raise SNR of echo signals so as to improve the targets detective probability. According to if the thickness and dielectric constant are know, this paper made a research on the impact of wall as obstruct on image formation and proposed two strategies to correct back projection method. After analysis on round trip time estimation error caused by that of wall parameters, this paper presented an iterative method on localization image to approach real position of targets.更多还原