High Dynamic Gps Signal Tracking Algorithm

GPS is widely used in many fields at present and it is playing a significant role inthe positioning and navigation domains. Under the high dynamic environment, theDoppler effects caused by the high speed and high accelerated motion have brought agreat challenge to the GPS signal acquisition, tracking and positioning. This has been thematter of concern in the GPS receiver algorithm research. Mainly aiming at the highdynamic application environment, this article researches the tracking loop optimizationand the GPS signal tracking method for the low earth orbit satellite positioning.Firstly, the paper explains the fundamental principles of GPS as well as itsapplication. The GPS signal acquisition method and the principles of GPS signaltracking loop-PLL, FLL and the DLL are also expounded in the paper. The influence ofthe high dynamic environment for the GPS signal tracking is taken into account. Basedon these, three subjects are researched in the paper, including the following:(1) The tracking loop optimization is studied in this article, aiming at reducing thethermal noise error and the dynamic stress error in the GPS signal tracking. Based on theanalysis of the code tracking loop dynamic performance, tracking loop optimizationstrategy is proposed that the loop orders and the bandwidth can be adjustedsimultaneously. In the algorithm, the loop orders are switched according to the LOSdynamic detection result, and on the principle of minimizing the thermal noise error andthe dynamic stress error, loop bandwidth adjustment is also implemented.(2) This article also studied the question that applying the adaptive Kalman filteringprinciple to realize the high dynamic signal tracking. In the research, the linear systemmodels are designed, and one Kalman filter is applied to complete the high-dynamicsignal tracking. In order to get good precision and stabilization, two real-time adaptiveKalman filtering algorithms are applied. On the Sage adaptive filtering theory, theapproach updates the noise properties of the dynamics and observation models basing onthe real-time measurements during data processing. The fading factor approach tries toestimate a scale factor to increase the predicted variance components of the state vector.(3) In view of low earth orbit satellite and its specific dynamic environment, themethod that Doppler frequency shift aids carrier tracking loop has been studied. Theresearch starting point is the satellite's orbit in the short time is approximately forecastable. So the method that the Doppler frequency shift which obtained using theforecast approach aids the carrier tracking loop is proposed. The method reduces thedynamics, thus bandwidth and loop orders can be reduced, and the integration time canbe increased. These measurements will greatly enhance the loop's ability to track weaksignal.High dynamic movement model has been designed. The model simulation isrealized both on the simulator and with the MATLAB tool. The simulated data have beenprocessed using all the discussed algorithms above. And the results indicate that thealgorithms work stably and have excellent performance.The article lays the algorithm foundation for the satellite-board and missile-boardGPS receiver's performance optimization, and has practical value for the receiverdevelopment in the specific application situation.