The Research Of Non-coherent Vector Tracking Technique In GNSS Receiver

In Global Navigation Satellite System(GNSS),vector tracking loop(VTL)can not only improve the tracking sensitivity,dynamic performance and bridge the signal after transient signal-loss,but also increase the accuracy,continuity of navigation solution by fusing the signal tracking and navigation solution computation(NSC).VTL can outperform scalar tracking loop(STL),thus is considered to be the key technology of the GNSS receiver of next generation.The research object of this dissertation is non-coherent vector tracking loop(NC-VTL),which can be realized easily in hardware to enhance the performance of GNSS receiver.Based on the shorting comings of existing research,the study for NC-VTL is conducted in Beidou Navigation Satellite System(BDS)in the following five aspects:construction of experimental platform,deep fusion algorithms for baseband signal processing(BSP)and NSC,algorithm design of NC-VTL,the performance analysis and evaluation for NC-VTL and the experimental test for NC-VTL.The related works are summarized as follows:To resolve the contradiction between channel parallel running and processing efficiency in MATLAB-based BDS software defined receiver(SDR),a pseudo-range measurement method based on "code phase prediction","channel distance monitoring" and "course timing" is designed to accomplish the pseudo-range measurement synchronously for all channels.This method can make BDS SDR simulate what really happens in hardware GNSS receiver,meanwhile maintain the processing efficiency.Three aspects of research work are contained in fusion algorithms for BSP and NSC.Firstly,the baseband functions,including acquisition,bit synchronization and signal transmission time initialization,are designed to be accomplished in navigation domain,aiming to increase robustness of receiver BSP.The concept of "virtual route" is proposed to derive the navigation filter(NF)aiding BSP algorithms which can be used to accomplish the three BSP functions.The NSC is coupled with other parts of BSP except for signal tracking to accomplish the more extensive fusion and mutual enhancement.Secondly,the error propagation equation of NF aiding algorithms are derived.The error source and propagation characteristic are analyzed.Thirdly,the theoretical analysis and experimental verification of the performance of NF aiding algorithms are conducted to show the improvements compared with traditional BSP algorithms.It can be concluded that the NF aiding can increase the performance of BSP functions and decrease the observation time.Four aspects of research work are contained in algorithm design of NC-VTL.Firstly,a set of vector delay locked loop(VDLL)algorithm is designed,which features directly calculating the code phase according to NF states.Secondly,the error propagation equation of NC-VTL is derived.It can be concluded that the proposed VDLL can reduce the requirement for "initial condition" and increase the robustness of the system.The price is that the atmosphere delay correction error results in code tracking bias which can be tolerated by NC-VTL.Thirdly,the code phase are adjusted to set value by "incremental adjustment",where time delay of hardware implementation are allowable.Fourthly,the system model,parameter configuration,operation sequence,algorithm flow,hardware implementation are discussed extensively and comprehensively.Four aspects of research work are contained in NC-VTL performance analysis and evaluation method.Firstly,the VTL and STL structures are compared in aspects of system model and residual model.The performance of VTL and STL are qualitative compared in aspects of information loss and auxiliary between satellites to show the advantage of VTL.Secondly,the analytical expression of code tracking bias of proposed NC-VTL are derived.Thirdly,in view of the disadvantages of analytical analysis and experimental analysis,the performance evaluation method based on semi-analytical framework for NC-VTL are proposed,which can fast accomplish tracking error analysis in flexibly designed scene for NC-VTL.Fourthly,based on the semi-analytical performance evaluation method,the performance of NC-VTL is analyzed with NC-VTL parameters selection and code tracking bias problem discussed.As for experimental test for NC-VTL,IF signals are collected from campus of Harbin Engineering University.The performance of STL,VTL and NovAtel GNSS receiver are compared.The channel monitor and elimination,re-acquisition,adaptive noise bandwidth technique are adopted in STL aiming at providing a more convincing control group.The NC-VTL outperforms the STL in signal tracking and navigation accuracy.The NC-VTL that processing the single BDS BlI signal can not outperform the NovAtel GNSS receiver which fuses the four GNSS signal in terms of positioning accuracy.However,NC-VTL can provide satisfactory positioning results under the condition that the dilution of precision of BDS satellite is not good.NC-VTL can avoid abnormal point of positioning and provide better horizontal positioning results in specified routes compared with NovAtel Propak6TM.Besides,the velocity accuracy of NC-VTL outperforms the GNSS receiver card contained in NovAtel SPAN-CPT.