The Research And Implementation Of Acquisition And Tracking Algorithm In Beidou-Ⅱ Navigation Signal

With the rapid development of BeiDou satellite navigation system in China,the research of receiver technology,especially the baseband signal processing algorithm has become the key to the development of navigation system.Behind the Bei Dou satellite signal system format,the core algorithm of Bei Dou receiver baseband signal including acquisition and tracking algorithm is deeply studied.First,the acquisition algorithm is studied in details in this thesis,we discussed the serial time domain acquisition algorithm,the parallel frequency capture and the parallel code phase capture based on FFT,the classic acquisition algorithm based on FFT is simulated and implemented.For the shortcomings of efficiency and computational complexity in traditional capture methods,a larger stepping based on PMF-FFT improved acquisition algorithm is proposed,using the partial matching filter add fast Fourier transform,the signal is segmented and then processed.According to the results of the measured signal processing,it can be optimized in complexity and computation,and the efficiency of the receiver is improved.After successful capture of the signal we discussed the tracking algorithm,according to the design of the system,the tracking loop is divided into two parts: carrier tracking loop and code tracking loop.In the design of carrier tracking loop,the phase locked loop and Costas loop technology are first studied,and the idea of the FLL assisted PLL is adopted to complete the carrier tracking.In the design of the code ring,using delayed lock loop technology.Through the coherent integration processing of the early,the prompt,and the late code,the code tracking is completed.Finally,we achieved the step-related capture technology on the FPGA,makes full use of the parallel data processing of FPGA to increase the relevant channels to improve the capture efficiency.The entire capture system is divided into carrier NCO module,local code NCO module,and operation unit module according to its function,and the arithmetic unit module.Each module is implemented using the Verilog HDL language in the Quartus II software,and functional simulation is completed in the Modelsim software.The results show that the algorithm can capture Bei Dou satellite signals effectively.