Optimization Of Signal Processing And Positioning Algorithms In High Dynamic GNSS Receivers

Global Navigation Satellite System (GNSS) is a space-based navigation system. When signals from more then4satellites are available, current user position can be estimated by GNSS receivers. The original goal of GNSS system mainly for military applications, including navy ships positioning, weapon transportation monitoring, etc. With the developing of high dynamic receiver technology, GNSS systems and other GNSS-centered integrated navigation system become more important in military navi-gation applications. Besides, high dynamic GNSS receiver also plays important role in aviation and space flight.In high dynamic applications, code and carrier doppler of received signal changes with the motion of vehicle. Jerk and higher order motions of the roving receiver may result in rapid changing of the carrier Doppler. It becomes a big challenge for the track-ing loops to keep precise tracking, or even to keep the signal demodulated correctly. Usually, the tracking loops for high dynamic receivers use large noise bandwidth to en-hance the dynamic stress. However, larger noise bandwidth also means larger output noise, which results in accuracy degradation of measurements and positioning results. In order to overcomes these problems, methods for fast code acquisition, carrier and code tracking, high precision positioning and track smoothing are studied in this thesis. Besides, a first look of positioning aided tracking loops is proposed.In the first chapter, basics of GNSS receiver and positioning algorithms are re-viewed. The error sources of GNSS system are also listed.In the second chapter, an orthogonal acquisition algorithm based on data compress-ing is proposed. It can dramatically reduce the computational payload while suffering limited loss in detection probability. Models of classical tracking loops in high dynam-ic receiver are reviewed. Then the tracking performances and the derivation of best equivalent noise bandwidth for second-order tracking loops are studied.In the third chapter, Doppler aided pseudorange smoothing algorithm is reviewed and the influence of Doppler tracking error on it is analyzed. A model-free Doppler-aided position estimation approach is proposed and the lower bound of errors of the approach based on the Cramer-Rao bound of the measurements is given. Simulation results and the error analysis show that the proposed approach may improve the accu-racy in position estimation.In the fourth chapter, an application of wavelet denoising in track smoothing is studied. Simulation results show that the performance of direct wavelet denoising dra-matically degrades in high dynamic applications. A novel wavelet denoising based track smoothing approach is proposed. The differential of position estimates based on code generated pseudoranges and carrier Doppler smoothed pseudoranges is used. Comparing to the positioning result of carrier Doppler smoothed pseudoranges, the proposed method shows smaller mean error. It also shows better accuracy while com-paring to the positioning result of code generated pseudoranges.In the fifth chapter, a steady state Kalman filter based estimator is proposed for receiver motion estimation. A design of positioning-aided tracking loop based on the estimator is given in the last part. Simulation shows that the carrier phase tracking performance may be improved, especially for jerk and higher order motions.The last chapter concludes the main contributions of this thesis and the research prospect of high dynamic GNSS receiver.