Research On Technique Of Acquiring Pseudo-random Noise Code In BDS

BeiDou Navigation Satellite System (BDS) is a global satellite navigation system which is researched and developed by our country and a more advanced satellite navigation system in current world, it has been widely used in many areas such as production, life, scientific research, national defense construction and so on. Capturing PN (Pseudo-random noise code) signal is the key feature to achieve satellite navigation and position in satellite receiver, also the speed of capturing PN can direct show the performance of satellite receiver, so this thesis will concentrate on the research of fast acquisition technology about PN in BeiDou Navigation Satellite System.This thesis researches several common PN acquisition algorithms, and compares one of them with the others. Then we obtain an advanced algorithm for the second generation BeiDou satellite signal receiver, which is a fast acquisition algorithm. This thesis mainly discusses the following aspects:First of all, this thesis introduces the development of global satellite navigation system, then describes the history of the BeiDou satellite navigation system, shows the importance of global satellite navigation system. And then this thesis proposes the research on BeiDou satellite receiver system, especially about acquisition technology of PN code signal.Then the thesis describes the theoretical basis of the BeiDou satellite navigation system, after the introduction to the composition of the BeiDou satellite system, it analyzes the constitution of BeiDou satellite signal. Then it analyzes the characteristics of the BeiDou signal in the parts of the carrier, PN signal and modulation mode. After introducing the BeiDou satellite system, this thesis analyzes the theory of BeiDou receiver signal acquisition and signal Doppler shift, the length of the code data, the frequency search length, capture threshold, and other important parameters involved in the acquisition process of signals.In the fourth part of the thesis, it analyzes commonly used signal acquisition algorithms, these are matched filter acquisition algorithm, serial acquisition algorithm, and parallel code phase acquisition algorithm. After studying their advantages and disadvantages, it proposes a combined acquisition algorithm based on partial matched filter with FFT, the partial matched filter with FFT algorithm converts the traditional two-dimensional search algorithm for signal pseudo-random noise code phase and carrier frequency process into one-dimensional process PN phase search, so it greatly reduces the time for signal acquisition. However, when the PN code signal with a longer period, this partial matched filter with FFT methods will consume large hardware resources. Considering the shortcomings of this capturing algorithm in the high dynamic environment and long period, then it proposes an improved method which uses the folded Matched Filters structure to achieve fast capture of long period code with small hardware resource consumption.Finally this thesis analyzes the principle and structure of folded matched filter, then uses the BeiDou II PN signal to simulate the system, validates the performances of the algorithm.