Research Of GPS Receiver Algorithm

This paper has introduced the GPS navigation positioning theory and algorithms. Also, the carrier tracking loop, navigation message access, solving the satellites' and the users' coordinates are expatiated and researched.By adding real-time operating system-μC/OS-II to the GPS receiver, which is researched and developmented ourself, GPS software are modularize and muti-threaded. That will keep the program adjustable and make the hardware resource effective. Base on that, further research is developed on the simulation of the PLL, algorithm for satellite orbit rapid extrapolation, application of Kalman filter method and so on.Simulation of the PLL makes reference to the hardware platform of GP2010. We have written a program by Matlab including frequency synthesizer module, the local carrier generation module, integrate and dump module, and discriminator algorithm module. Through the simulation of input errors, we analysed the characteristics, advantages, and disadvantages of the various discriminator algorithm based on comparative. At the same time, on the request to the data refresh rate in high dynamic environment, the paper deduces the rapid extrapolation algorithm of the orbit to replace dynamic model method. According to the Taylor lauched formula, the rapid extrapolation which ignores the residual term, will calculate the satellites' coordinate by plus-minus operation. At the meanwhile, through the introduction of Kalman filtering algorithm, giving the equation of state and measurement to establish the Kalman filter model, That will make the result of users' coordinate more precise by eliminating the random error, which aroused by the measured data.