Analysis And Parameter Estimation For Satellite Navigation Signals

With the wide application of the satellite navigation technology in modern society, it is desirable to increase the accuracy of navigation. The satellite navigation system takes advantage of the time of arrival(TOA) to achieve its functions, such as positioning, navigation and timing. The observed accuracy of TOA is influenced by the satellite navigation receiver. Signal acquiring and tracking is critical for the satellite navigation receiver, because the performance of the receiver is determined by their accuracy. At present, there are several navigation systems and these systems are not transparent. The navigation across systems inevitably involves the cracking of the pseudorandom niose(PRN) codes, and the cracking is considered as a problem of parameter estimation. Therefore, this thesis focuses on the analysis of the satellite navigation signal and estimation of related parameters. The main research contents will be shown as follows:Firstly, based on the linear theory, a closed-form expression for optimum despreading chip waveform is derived to minimize root mean square tracking error. The Cramer-Rao Lower Bound(CRLB) is also presented from which a characteristic of the spreading chip waveform is obtained and the characteristic could help reduce the tracking error. Due to this, the optimal despreading chip waveform is applied in the new GPS M code signal. Secondly, it is shown that the navigation signal can be assumed to the single-tone complex sinusoidal signal if the navigation bit information and spreading chip waveform are given. There are many frequency estimation algorithms for the single-tone complex sinusoidal signal. A new algorithm for frequency estimation is proposed which has a better performance than all existing algorithms and closely follows the CRLB. Finally, knowledge of the PRN code is a prerequisite for designing receivers, so cracking the PRN code is studied in this paper. In order to extract the PRN code chips out of the noise, the paper correlates the whole data with a small slice of itself and stacks muliple periods of the PRN sequence. Using the signal processing, several parameters in satellite navigation signals, such as the code period, Doppler frequency, initial phase, the start of the code and so on, are estimated. PRN codes are cracked at the end of the paper.