Research On Acquisition And Tracking Algorithms For GPS Weak Signal

Global positioning system can supply the service which includes position, velocityand time for people. But in the city streets, forest, gorge, indoor environment and so onsignal being obstructed, GPS signal level suffers a great loss. The ordinary GPS receivercan not work properly in such a weak signal conditions. Therefore, high sensitivity GPSreceiver technology has gradually become one of the hotspots of GPS technologydevelopment and application of research in the field today. At the same time, the signalacquisition and tracking technology are the key technologies of the GPS receivertechnology, therefore, developing the research of acquisition and tracking algorithm ofGPS weak signal has a good academic value and important theoretical significance.Firstly, this paper descirbes the constitution of GPS signal, which is constituted bynavigation data, C/A code and carrier, and it is that C/A code high autocorrelation andlow cross-correlation is the basis of successful capture of GPS signal. Because of theimpact of Doppler, the frequency range of the GPS signal acquisition search is-10kHz~10kHz. Then analyze the impact of GPS signal acquisition which is about theavailable maximum data length and the step of Doppler frequency. Research andanalyze the acquisition algorithm of Tong search detectors, coherent-noncoherentaccumulation and differential coherent accumulation, and simulate the relationshipbetween the sensitivity of acquisition and the number of mean residence of Tong searchdetectors algorithm under different condition of A and B by the Matlab software,and simulate capture effect of coherent-noncoherent accumulation algorithm anddifferential coherent accumulation algorithm.In this paper, make the original the Tong search detector algorithm a improvementwhich adds the adjacent the square of coherent integral as a new statistical test variable,so improve the acquisition sensitivity of GPS signal, but increase average dwell numberof each unit, and extend the time of GPS signal acquisition. Adopt3rdPLL on assistanceof2ndFLL for the structure of carrier tracking loop, and it is possible to track the GPSsignal whose carrier to noise ratio is30dBHzand acceleration is12g low carrier tonoise ratio and high dynamic GPS signal, and correctly demodulate the navigation data.