Time Delay Estimation Of Narrowband Radio Signal In Wireless Passive Location

With the rapid development of wireless communication system and more and more attention paid to life security, the antiquated wireless location technology has new vital force and brings a lot of new problem. So it becomes a hot spot in location field. Under the common efforts, the wireless location technology is developing fast. Its effects are more and more important in national safety and navigation. The main content of this thesis is about time delay estimation (TDE) in passive wireless location. In the wireless localizing methods, the passive locating is paying more and more attention because of its high confidentiality and flexibility. The TDE method in passive wireless location is the key part, and its precision and efficiency directly affect the performance of the locating system. Therefore, doing the research thoroughly to it has important significance in both theory and application.This thesis systematically studies the TDE theories and methods which have existed. Based on analyzing their principle and the good and bad points, three new TDE methods are presented. The organization is as follows:Firstly, the characteristic, meaning, history and actuality of passive wireless location are reviewed, as well as the basic conception, locating model and assessing guidelines of TDE. Besides, several existed TDE methods are introduced briefly.Secondly, TDE of the special signal which is called narrow band radio frequency (NBRF) signal in passive wireless location is discussed, based on the application background of the thesis. The problems in the time domain and frequency domain methods for the TDE of NBRF signal are analyzed.Thirdly, the application of wavelet transforms in TDE is discussed. Based on the time shift property of Continuous wavelet transforms (CWT), the conclusion is given that most of existing algorithms for TDE can be combined with CWT. The application of discrete wavelet transforms is also considered, and thesis gives an algorithm of double-weighed generalized correlation method based on DWT.Fourthly, the thesis gives a method that transfer the delay information from source signals into the correlation of theirs by correlation computing, based on the bandwidth characteristics of NBRF signal and the estimating formula of correlation. The more precise result can be derived from the disposing of the cross-correlation of signals. The theoretical analysis and stimulation show that the algorithm has advantageous anti-noise performance and much more invulnerable to the impact of bandwidth.Fifthly, the problem of carrier frequency deviation in the independent receivers is analyzed. To reduce its negative influence on the successive TDE method, the thesis picks the envelopes of source signals, based on the property of Hilbert transform of narrow band signal. And the Kalman filtering phase algorithm is used to get satisfactory estimation results.Finally, the thesis make tests on actual received signals, and the summary of all the research content is given, as well as the next step work.