Research On Location Technology Based On TDOA And TOA

Precise location of targets plays a very important role in the military and civilian systems. The problem related to the target location which includes active location, passive location and self-location has received considerable interest for many years. Among them, passive location determines the target location information by measuring the electromagnetic radiation from radiation sources(communication transmitters, radars, etc.), where the stations do not emit electromagnetic waves. Its positioning mode shows that passive location has the advantage of strong concealment, thus making it an important part of modern integrated air defense systems, remote warning systems as well as airborne enemy defense systems, etc. In addition, passive location is playing an increasingly key role in the field of electronic warfare. The commonly used parameters for target location mainly include time difference of arrival(TDOA), time of arrival(TOA), angle of arrival(AOA), and their hybrids.On one hand, this dissertation studies the TDOA based and TDOA/FDOA based localization algorithms for stationary and moving targets, respectively. For stationary targets, several classical passive location algorithms based on TDOA measurements are introduced, and the positioning performance of each algorithm is compared as well. For moving targets, we put emphasis on several joint positioning algorithms based on the TDOA and FDOA measurements.On the other hand, this dissertation also introduces a multi-dimensional scaling(MDS) method for TOA based target localization. Subsequently, a novel improved MDS location algorithm is proposed by employing asynchronous TOA measurements, which provides higher positioning accuracy. The main work of this thesis can be summarized as follows.(1) A brief introduction of the background, the significance, and the current situation of passive location is made in chapter 1. Then we describe the mathematical models of target location and introduce several classical location methods in detail. Finally, we study the performance evaluation of positioning accuracy for a variety of localization algorithms.(2) Chapter 2 introduces the basic principles of TDOA location algorithms and the main methods for estimating the TDOA measurements. Besides, we compare three well-known TDOA location algorithms, including weighted least squares(WLS) algorithm, Taylor series method and Chan algorithm.(3) In chapter 3, a multi-dimensional scaling(MDS) analysis algorithm and its application in the TOA based target localization problem are introduced. Then on the basis of the MDS algorithm and the TOA positioning model of multiple moving base stations, we propose an improved MDS location algorithm which employs the position information of the multiple base stations and the asynchronous TOA measurements. The proposed algorithm considers the effect of the second-order error term, thus offering higher positioning accuracy.(4) Chapter 4 focuses on studying the location algorithms for moving targets. Firstly, we introduce several frequently used joint localization algorithms based on TDOA and FDOA measurements. In addition, we analyze and compare the accuracy of the target position and velocity estimates of each localization algorithm respectively.