| Satellite navigation is playing an important role in the field of national economyand military. As the improvement of users’ navigate receiver requirements, thetraditional scalar tracking (ST) has difficulties to meet the requirements. As anemerging technology in satellite navigation field, vector tracking (VT) has manyadvantages. VT processes all satellite signals insight as a whole through softwarereceiver, which doesn’t increase the receiver’s hardware. Compared with the traditionalscalar tracking, the advantages of VT are as follows: bridging the instantaneous lossingsatellite, enduring lower carrier power to noise density (C/N0) of receiving signal,controllable tracking dimension and so on. VT is attracting more and more attention,and VT would be one of the key technologies used by the next generation receiver.Relying on certain weapon and equipment pre-research fund and some outsourcingprojects, this dissertation deeply researches some key technologies of VT. The mainresearching contents are as follows:1．The problem of VT’s parameters initialization is investigated. Firstly, the basicsof VT parameters initialization are introduced, including software receiver, signalacquisition, signal tracking, navigation data abstraction and pseudo range solution, etc.Secondly, for the problem of frequency refinement, the dissertation describes the basicprinciples and steps of the traditional phase difference (PD) method, and analyzes thismethod’s performance limitations. On this basis, the dissertation proposes adifferentially coherent frequency refinement algorithm (DCFR), and gives thealgorithm’s principle and detailed implementation steps. Finally, the performances ofPD and DCFR are compared and analyzed by theory and simulation.2． The dissertation establishes VT’s system model, and derives the modelparameters. Firstly, the differences between ST and VT are explained from horizontaland vertical respects of software receiver architecture. On this basis, the dissertationgives VT’s implementation diagram and data flows. Secondly, for the tracking ofpseudo-code and carrier doppler shift, the dissertation sets up vector delay lock loop(VDLL) and vector frequency locked loop (VFLL) system model, and derives the linearmeasurement equation, the corresponding measurement matrix and the measurementerror covariance matrix. Finally, the validity of the system model and the parameters aretested by simulation from three aspects: bridging the instantaneous lossing satellite,enduring lower C/N0of receiving signal, the impacts on VT by the number of losingsatellites. Additionally, the performance differences between ST and VT are comparedand analyzed.3．C/N0estimation of VT is investigated. Firstly, the dissertation introduces and summarizes three traditional methods for C/N0estimation, analyzes their estimatedperformance, comes to the conclusion that additional noise channel method (ANCM) issuitable for VT, the reasons why the other methods can not suit for VT are also given.Secondly, the dissertation comparatively analyzes two specific C/N0estimation methodby theory and simulation, the two methods are squaring estimator and differentialestimator, which belong to ANCM. Finally, for the problem of mutational C/N0estimation, the dissertation proposes an adaptive C/N0estimation method. The mutationof C/N0can be detected by the statistics: mutation in certain time window (MTW).When MTW is an ordinary case, C/N0is estimated by differential estimator, which hashigher computational efficiency; when mutation occurs, C/N0is estimated by strongtracking filter, which has finer estimated precision. The adaptive method can satisfy notonly VT’s requirements of estimation precision but also computational efficiency.Some crucial theoretical problems and technological issues in VT are investigatedsystemically in this dissertation, and, the solutions and conclusions are put forwardcorrespondingly. These research findings are very significant in both theory andengineering. |
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