Acquisition And Tracking Algorithms For BOC Modulated Signals In High Dynamic Environments

As a novel navigation signal modulation method, the binary offset carrier(BOC) modulation is able to facilitate the compatibility between available satellite navigation systems. It not only improves navigation positioning accuracy, but also enhances the ability to resist the multipath and interference. However, multiple auto-correlation peaks of the BOC modulated signals cause the ambiguity problem. To solve this problem, it is required to investigate a new signal acquisition and tracking algorithm. Moreover, it is a challenging issue to capture and track satellite navigation signals in high dynamic environment. Therefore, it is an urgent requirement for the Beidou navigation system to study the acquisition and tracking algorithms which are applied to high dynamic environment.In this thesis, unambiguous acquisition structure, acquisition algorithm and tracking algorithm of BOC modulated signals are studied under high dynamic surroundings. The main contents of this thesis are summarized as follows:1. By analyzing BOC modulation signal characteristics, an unambiguous acquisition structure for BOC(n,n) signals is proposed. Simulation results show that the performance of this new unambiguous structure is 2d B lower than that of the existing structure with best performance, but it has certain advantages on computational complexity, especially when it is combined with the parallel code acquisition algorithm.2. An improved parallel code acquisition algorithm which is combined with the new unambiguous structure is put forward for BOC(n,n) signals. Simulation results demonstrate that the performance of this improved algorithm is 2d B lower than the all-sampling FFT algorithm. However, it has obvious advantages on the computational complexity, hardware implementation complexity and acquisition time, especially when the sampling frequency is very large or the FFT points is not an integer power of 2.3. An unambiguous code tracking scheme is proposed for BOC(n,n) signals. Simulation results show that this proposed code tracking scheme is effective. A novel high dynamic carrier tracking scheme based on fuzzy control principle is designed for BOC modulated signals, and a comparison with the performance of the 3-order PLL is also provided. The results show that this carrier tracking scheme has the features of smaller tracking lock time and better high dynamic adaptability, and that it can obtain satisfactory carrier tracking accuracy.