| With the global networking of the BDS-3 satellite navigation system,the BDS system has achieved all-day,high-precision timing,positioning and communication functions.The improvement of satellite navigation service performance is mainly reflected in the optimization of terminal technology,especially the improvement of receiver accuracy and stability in specific scenarios.However,the acquisition of scene-specific real signals requires a lot of human and material resources,and the signals are relatively fixed,and it is impossible to adjust the subtle parameters and channel changes in the signals,and the signals under extreme conditions such as high dynamics are not available for real acquisition.Soft analog sources can provide accurate and flexible input of parameters such as navigation signal quality and track to meet the various complex propagation environments and changes in signal details parameters during the development and testing of reception algorithms.The changes in signal quality are mapped by flexibly adjusting the signal parameters.In this context,this paper conducts research work on the design and implementation of a soft analog source for civil signals at the B1 frequency point of BDS,with the following main contents.(1)To provide the correct signal element parameters for the development of the soft analog source and to optimize the signal positioning accuracy,the system modeling of the BDS satellite constellation orbit is performed by interconnecting STK and Matlab.The satellite visibility and GDOP value variations in various regions of the world are analyzed,and a new redundancy degree star selection algorithm is proposed to optimize the positioning solution efficiency of the simulated source and simplify the simulation operations while guaranteeing the signal positioning accuracy;the detailed parameter design of the simulated signal is completed by orbit model extrapolation,which provides a reliable parameter input source for the subsequent development of the signal simulation source software.(2)Based on the Matlab platform,a signal soft simulation source is built,and based on the research of satellite orbit modeling and signal parameter design,the full-link modeling of satellite navigation signals with different satellite states and different propagation environments is realized.The orbit-based modeling optimizes the positioning accuracy of the simulated signal,and the parameter design ensures the realistic and accurate simulated signal.The software realizes the simulation generation of signal elements such as signal ranging code,navigation message,message encoding and modulation mode.By establishing a complete signal propagation model,the errors caused by Doppler shift,multipath,ionosphere and noise in the signal propagation process are simulated.The simulation source can flexibly change the parameters to achieve multi-scene and full-link signal generation.(3)The simulation of ideal signals,simulated real environment signals and different types of dynamic signals is completed by using the soft simulation source,and the simulated signals are captured,tracked and positioned for analysis to verify the accuracy of the simulation of signal elements and error modeling of the simulation source.The software receiver loop tracking,pseudo-range measurement and localization results of the real and simulated signals are comprehensively compared,and the results show that the simulated signal generation results match with the theoretical analysis. |
