Algorithm And Implementation Of Simplistic GPS Signal Acquisition And Tracking

Global Positioning System(GPS) is the abbreviation of NAVSTAR / GPS,which is the prefix abbreviation of Navigation Satellite Timing and Ranging / Global Position System.GPS is currently the most advanced precise satellite navigation and positioning system.The project is the sub-part of "The Design of GPS Receiver", the ultimate goal of the whole project is to design a chip for acquiring the precise time, embedded in a watch.The core of the whole project is to design a simplistic acquisition and tracking structure,which can be realized reduction by hardware.Based on analyzing the traditional acquisition and tracking algorithm,the simplistic acquisition and tracking algorithm is proposed,and its feasibility is verified.This paper introduces the princilple of acquisition and tracking as well as the generation of GPS signals,and followed by some comparisons among the traditional acquisition and tracking algorithms.Based on these theories,a variety of simplistic programs have been proposed.Each program can achieve acquisition and tracking,and each of them has innovation compared with traditional program.Through analyzing their advantages and disadvantages,then improving,finally,the new acquisition and tracking program with the best performance and the simplest structure has been determined-the program of recognizing navigation message based on phase transition.This paper focuses on the three items that greatly improve the power,the efficiency, the area and the reliability of the traditional programs:(1) The use of FFT-related operation is avoided in order to realize the hardware reduction.(2) It combines the acquisition and tracking algorithm together.(3) It uses a fixed local oscillator frequency with Doppler shift to identify the transition of ephemeris code through the transition of phase,according to this,the navigation message has been demodulated.The hardware cost of carrier tracking loop is reduced greatly,thus reliability is improved.Subsequently,through the expansion,the limitation of this algorithm has been solved. It enables to cover all values of Doppler shift,that is,it can acquire and track all the GPS stars.The noval algorithm has been verified by the use of Matlab platform.The verification process includes the generation of GPS IF signal,the functional test of the acquisition and tracking algorithm,the demodulation of the navigation message.The result indicates that the noval algorithm is valid.It achieves the expected goals.At last,ways of the realization of acquisition and tracking is mentioned.