| GPS statelite navigation-orientation system is a real, all-weather, globe, real time, high-definition navigation system based space. It can provide precise three-dimensional position, velocity and time. Mordern satellite navigation system provides high precise time information and navigation service in military and became an important part of ocean succor and car navigation for civil.The present papers focus on GPS carrier synchronization, which put a great effect on system performance, especially under the condition of low signal noise ratio and great doppler frequency shift. In the paper related methods to carrier synchronization in GPS system is summarized with a systematic view and analyzed to give out a design guide.There are plenty of researches on low dynamic target track for GPS. The traditional DS receiver always uses a delay locked loop (DLL) to synchronize the PN code and then uses a Costas loop to realize the carrier synchronization. The closed-loop structure not only takes long time to realize the synchronization but also has the defect of "hang up". This paper took a tracking structure which PLL is (Phase locked loop)assisted with FLL(frequency locked loop) and also dealt with false lock. The simulation gave a good performance.In recent years, with the development of the DS-SS and the theory of all digital receivers, the open-loop structure based forward estimation attracts more attentions. A new synthetic frequency estimation algorithm of single-tone is proposed. It is derived from the interpolated FFT with window in combination with correlation function. The result of simulation proves that it can replace the Costas-loop in the traditional DS receiver to realize the carrier synchronization.The research results of the satellite signal receiver's carrier-track techniques in this paper can be applied in the signal processing techniques of the modern satellite navigation and communication systems, which are of great theoretical importance and use value. |
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