Research Of Acquisition And Tracking Algorithm For GPS Signal Based On FPGA

In this information age, not only the mobile phones people used and the car navigation but also the military equipment of the state are inseparable from navigation and positioning.And global positioning system (GPS) is undoubtedly the most outstanding system in the global navigation satellite system. GPS is able to complete the task that is navigation,positioning and timing, could not be separated from acquisition and tracking for the GPS signal accurately. Research of acquisition and tracking algorithm for GPS signal is not only conducive to the navigation but also a good reference for the development and improvement of Bei Dou satellite navigation system which is in our country.In the first, this paper introduced the development, composition and working principle of GPS, then introduced the spread spectrum communications and its application in GPS. Apart from the above, this paper analyzed the carrier signal, pseudo random noise code, navigation message and the generation of GPS signal.In the field of researching of acquisition algorithm for GPS signal, this paper analyzed the influence of different parameters on the accuracy, speed and ability of acquisition algorithm for GPS signal, and selected the parameters for the acquisition algorithm. This paper analyzed the time-domain sliding correlation acquisition algorithm and fast acquisition algorithm in frequency domain, and illustrated their advantages and disadvantages and applications. The fast acquisition algorithm in frequency domain is used as the acquisition algorithm in this paper. Aiming at the shortcomings of fast acquisition algorithm in frequency domain on FPGA, which is that the FFT module and the IFFT module resource consumption is too much. This paper used the FFT module to achieve the function of IFFT. The comparison of resource usage tables proved that this method is very effective. At last, This paper simulated the fast acquisition algorithm in frequency domain on FPGA and given the view RTL schematic.In the field of researching of tracking algorithm for GPS signal, this paper given a detailed design of carrier signal tracking loop, pseudo random noise code tracking loop and complete tracking loop. Then this paper analysed each modules of the complete tracking loop.Based on theoretical analysis, this paper design the module of carrier signal NCO, the module of carrier signal generator, the module of pseudo random noise code NCO , the module of pseudo random noise code generator, the module of integrator , the module of carrier signal loop discriminator phase, the module of pseudo random noise code loop learning phase, the module of carrier signal loop filter and the module of pseudo random noise code loop filter.Then the view RTL schematic of each modules is given. Through the optimization and synthesis of each module, a complete tracking loop is formed. Then the view RTL schematic of complete tracking loop is given. Finally, the simulation of acquisition and tracking algorithm for GPS signal on FPGA is presented. Simulation results showed that the acquisition and tracking algorithm for GPS signal can successfully recover the navigation data.The results showed that the method of this paper is correct.