Study Of Through-Wall Target Localization Method Based On IR-UWB

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.