On The Acquisition And Carrier-tracking Algorithms Of Beidou Signals

Bei Dou Navigation System is a global satellite navigation system with independent intellectual property rights and autonomous control of region developed by China. It can offer users all kinds of services such as positioning, navigation and timing with high accuracy. The B1 band signal of Bei Dou MEO/IGSO Satellite is modulated by NH code,which leads to the increased risk of signal flipping and brings a series of problems to the capture and tracking of Bei Dou signals.Based on analysis of the characteristics of the Bei Dou signal, this thesis focus on the acquisition and tracking algorithm.The main contributions are as following:1. The FFT-based code parallel acquisition method and the rapid acquisition method based on Partial Matched Filter(PMF) and Fast Fourier Transform(FFT) are analyzed and their limitations to Bei Dou MEO/IGSO signals get the argument.2. Two C/A code acquisition algorithms based on the code parallel acquisition algorithms are designed. In order to improve the carrier frequency estimate accuracy,this thesis has designed a method by combining “FFT-based code parallel coarse acquisition ”and “frequency serial fine acquisition”. The proposed method reduces the acquisition error of carrier frequency at the cost of a small increase in acquisition time and computation complexity. Simulation results show that the designed methods work well.An improved acquisition method based on Partial Matched Filter(PMF) and Fast Fourier Transform(FFT) is designed. Compared with the previous algorithm based on the differential PMF-FFT algorithm,this method brings an improvement of 2d B in terms of acquisition.3. This thesis also designs a tracking loop for Bei Dou signal. In the proposed tracking loop, the Phase discriminator and Frequency discriminator can overcome the problems caused by NH code modulation. In order to meet the requirements of the tracking performance, the combination of the third-order PLL and the second-order FLL is used for Carrier tracking loop. The simulation results show that the tracking loop provides satisfied tracking performance.