| Summary: | 碩士 === 國立交通大學 === 機械工程系所 === 102 === In Global Positioning Systems, we need to receive the signal transited by satellite for positioning. Because of the relative motion between satellite and receiver and transit time, it will cause the frequency shift and time-delay of the signal. We must lock the frequency and time-delay of the signal precisely for acquiring the information for positioning. So we need to reach the goal by using Phase Locked Loop.
This paper majors in the analysis of the frequency range which can be locked by Phase-Locked Loop, using limit cycle to understand the locking situation of different controllers, and designing system parameters by transfer function of the PLL system.
Because we hope to implement the analysis result of Phase-Locked Loop to software-defined GPS tracking system, we analyze the loops of tracking system and utilize the parameters designed method to tracking system. Besides, in order to implement the GPS system to rocket, we analyze the satellite motion, and the effect between satellite motion, rocket speed, rocket acceleration and the satellite transmit signal. The range of the Doppler frequency is about ±21kHz when rocket speed reach 10Ma,and the change of the Doppler frequency will reach 515.57Hz/s when rocket acceleration reach 10G.
Finally, we will use simulation to find the system nature frequency which is needed by different rocket moving situations. This paper using Matlab to compile the algorithm of software-defined GPS tracking system,and utilizing the designed method to design system parameters. We not only verify the feasibility of the algorithm, but also observe if the simulation results fit the designed specifications.
Finally, in order to improve GPS tracking systems, the method of changing the tracking loop is proposed in this paper, and will verified by simulation.
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