Research On Beidou Reciever Tracking Algorithm And Applications

Beidou satellite navigation system is developed independently by China, which can provide the services of location, navigation and timing around the clock. To speed the development of Beidou satellite navigation system, the research into algorithm and application design of Beidou receiver are very important parts.Tracking is one of the most important parts during signal processing stage of the navigation receiver, only when the receiver locks the satellite signal, can the navigation information be demodulated, thus achieving location. When high-speed relative movement exists between the satellite and receiver, a large doppler frequency shift may be produced, and the change of the relative velocity can lead to the change of signal frequency in the tracking stage, when the frequency change is beyond the scope of tracking loop traction, it’s easy to result in tracking failure. Therefore, signal tracking under high dynamic environment is a challenging and valuable research direction.This thesis first analyzes the structure of Beidou satellite signal, and it simulates to produce the process of Beidou intermediate frequency signal, then it analyzes the effect brought to signal tracking of high dynamic. This thesis also introduces in detail three methods of identifying the phase of Costas PLL, then it analyzes three methods of identifying the frequency of FLL, and three methods of identifying the phase of DLL are given here. Soon afterwards the simulation of these methods and the performance comparison of each other are given. Later, this thesis expounds the working principle and design method of loop filter and numerically controlled oscillator. Based on the simulation and research on measurement error in the tracking loop, this thesis analyzes the settings of trace threshold and the selection of the loop bandwidth, thus determining the range of the bandwidth which meets the high dynamic tracking loop.On the basis of the above analysis, this thesis puts forward a method of tracking in high dynamic environment. In the method, the four phase discriminator first tracts the frequency fast, thus narrowing the frequency difference, making it enter into the working scope of FLL, then PLL is assisted by FLL for precise tracking. FLL assists PLL in parallel and serial way. This thesis simulates Beidou intermediate frequency signal, producing four kinds of signals in high dynamic environment. They are fixed frequency, frequency of mutations, frequency of an oblique rise and frequency of twice rises. Under the dragging of the four phase discriminator, the thesis makes tracking experiments of the four kinds of signals in both parallel and serial ways respectively, thus verifying the feasibility of the method. On the basis of the comparison and analysis of the method achieved in the two different ways, the thesis gives the applying environment of the different assisting method.Finally, the thesis designs a kind of information acquisition system based on Beidou. The system can collect the temperature, humidity and dust in the environment, as well as the local latitude, longitude and time, it can also transmit the information to the server to facilitate follow-up study of data analysis. According to the system function, the thesis designs the system architecture, which includes a MCU, the acquiring modules and the network transmission module. As the core of the system, MCU is used to read data from the acquisition module and control the transmission of the network transmission module. The network transmission module connects with the server for communication based on TCP/IP protocol. On this basis, the detailed design process of the hardware and software of each module is given. Finally through the operation of the system, a better real-time performance of the system is verified.