Investigation Of Passive Location Techniques Based On OFDM Signal

In recent years, more attention has been focused on passive radar systems for their "silence", i.e.-no transmitting electromagnetic waves. Passive radar systems based on civil FM radio and TV signal have made great progresses due to their advantages, such us wide range, better concealment, anti-stealth, anti-extra-low flight. Orthogonal Frequency Division Multiplexing (OFDM) has been widely used in many systems such as digital audio broadcasting system (DAB), digital video broadcasting system (DVB) and wireless local network (WLAN) for its abilities to anti multi-path interference and high spectrum utilization ratio, and has become one of the core techniques of the next generation wireless communication system. In this thesis the passive location systems based on digital audio and video broadcasting signal using OFDM modulation are studied.First of all in this thesis, the research status of passive location techniques is introduced based on the study and analyses of a lot of related literatures. The taxonomy for passive location system and basic techniques are analyzed, and some representative research fields and content in this domain are also introduced.Secondly, the principle and key techniques of OFDM and its applications in DAB and DVB are introduced, and then the sensitivity of OFDM system to synchronization is analyzed. It is shown that OFDM receiver system needs better precision of frequency and timing. So the time of arrival (TOA) of OFDM signal can be gotten by accurate estimation of timing, and can be used as the ranging technique of passive location.Because the principle of timing estimation and ranging is the same on the whole, so two kinds of timing estimation techniques, one is based on the circle prefix and the other is based on pilot sequence, and its application in ranging is discussed. Two proposed algorithms are also analyzed in detail.Finally, we build a passive location system model, deduce two 3D TDOA location algorithms using in the passive location system, simulate the performance of these algorithms, the high precision results validate the effectiveness of the algorithms.