Research And Implementation Of Tracking Technology In GPS Civil L2C Signal

In order to further strengthen GPS competitiveness in the global civil navigation market, the US government decided to make adjustments to the GPS civil signal, and introduce three new civil singal L2C, L5and L1C. Two channels of data/non-data, longer PRN code, message error correction coding and lower data rate are used, in order to improve tracking threshold of signal and optimize the correlation of signal. Despite the new L2C civil signal has been opened, but at present most GPS receivers do not have the ability to receive the new signal, the domestic research for L2C signal tracking technology is also still nothing. Therefore, it has a very important significance to design and implement L2C tracking technology.First of all, based on summarizing the development situation of GPS signal in domestic and foreign, the technology of civil L2C signal tracking and the technology of Kalman filtering are analysed in this paper, and the basic composition principle of GPS receiver is stated, and the generation process of GPS civil signal L1C/A code, L2C code and L5code are described and compared in detail. Then, according to the principle of classic analog phase-locked loop, the tracking design ideas of first generation GPS civil signal C/A code are provided, and the optimal tracking loop discriminator and filter are selected. Next, based on the characteristics of introduce data/non-data two channels and increase clear integration time, L2C signal tracking loop design ideas and the implementation process of tracking module are provided, and the error in discriminator of CM code, CL code and C/A code in the tracking loop are analysed and compared. L2C signal tracking module is simulated and achieved by using matlab, the tracking results of fixed-frequency signal, frequency ramp signal and frequency acceleration signals by using the data channel and non-data channel are verified, the The advantages and disadvantages of single channel tracking method and fusion tracking method are analysed. Finally, the principle of Kalman filtering, the causes to lead it divergence and the limitation of adaptive filtering in high dynamic are described in detail, and a second-order adaptive Kalman filter algorithm taking high dynamic and accuracy errors into consideration is provided by combining the advantages of two filtering methods, and the optimization results of tracking frequency ramp signal are verified, and weight coefficient initial value of state equation and observation equation in motion model are adjusted, and the output results of code tracking loop discriminator is tested, and the effective tracking strategy of Kalman filtering for L2C signal is provided.