The Study Of GPS Software Receiver Acquisition And Tracking Technology

In recent years, the GPS has been widespread used in the field of civilian navigation and surveillance, traffic management, surveying and mapping science and technology, precision agriculture, leisure tourism, besides the rapid development of other satellite navigation system. For the shortcomings of conventional hardware implemented GPS receiver, which can not adapt to its rapid development, in this paper a new way was proposed, that the idea of software radio was added into the design of GPS receiver, and the acquisition and tracking technology of GPS were deeply studied.In this paper, firstly the constitute of the GPS system, signal structure and simulation method of digital IF signal have been studied. The similarities and differences of the constructs between traditional hardware implemented GPS receivers and GPS software receiver have been discussed. The advantages of the software receiver, the C/A Code Generation and its correlation, and the noise model of GPS signal have been elaborately described. Meanwhile, the Digital IF signals have been simulated under different environments.Secondly, the principles of GPS signal acquisition have been studied, then detail analysis of capture process has been made, which contains four main parameters:Doppler search space, Capture data length, Step length and Capture Threshold. Three kinds of acquisition algorithm have also been studied, which include traditional GPS signal acquisition, FFT capture based on code phase and PMF-FFT capture. Emphatically the capture performance that caused by the length of sub-correlator and FFT operational points of the PMF-FFT capture algorithm have been discussed. In view of the low frequency resolution of the PMF-FFT capture algorithm, in this paper, a new way to promote the frequency resolution has been proposed, which make the least-squares curve fit to the maximum peak of the output of the PMF-FFT amplitude-frequency response, then give out the simulation results.Finally, phase-locked loop, carrier tracking loop and code tracking loop have been studied, then two-order-locked carrier-assisted three-order phase-locked loop and two-order DLL code tracking loop combination loop have been designed.Loop bandwidth which effect the stability of tracking loop and the update time parameter selection of Loop frequency have been discussed in detail. Meanwhile, the tracking simulation of the signal has been given out.