Research And Verification On Key Techniques Of BeiDou Satellite Positioning Signal Waveform Simulation

The BeiDou satellite navigation system is now in the stage of global networking,and the BeiDou system is gradually applied to areas of national economic and social development.For the test of BeiDou satellite signal receiver,satellite navigation signal simulator has become a significant test tool for BeiDou receiver due to its advantages of loadable configuration,free from geographical and scene constraints and high stability.Based on the key technology of BeiDou navigation system and combining the mobile wireless satellite communication channel simulating technology,a software-defined multi-frequency BeiDou satellite navigation signal simulator is implemented.The main work of the thesis is as follows:Firstly,for the major systems in GNSS,GPS,GLONASS and BDS are systematically summarized.We contrastively analyze the developing process of each system,system composition and main functions,constellation and orbit distribution,and signal characteristics of each system.The fading characteristics of mobile wireless satellite communication channel are expounded and the typical Lutz satellite communication channel model based on experimental statistics is analyzed in detail.Secondly,the technical requirements of the satellite signal simulator are carried out and the key techniques of satellite navigation signal simulation are analyzed.We study the positioning principle of the BeiDou satellite navigation system,and establish error correction models for factors affecting the positioning accuracy,including satellite clock error,ionospheric error and tropospheric error.Then the conversion of time system and coordinate system involved in satellite signal simulation is introduced.Next the meaning and corresponding algorithm of ephemeris parameters in navigation message is illustrated.Finally,we research on extrapolating the ephemeris parameters at any time based on least squares method according to the observation files of precise ephemeris parameters and demonstrate the error of the fitting algorithm is within lm.Then,the waveform link of BeiDou-2 B1I signal and BeiDou-3 B1C signal is designed and simulated.According to the B1I signal and the B 1C signal standard,the structure of the data frame,the structure and feature of the ranging code sequence,the encoding principle and method,the modulation principle and the multiple access mode are studied in detail.Then the waveform link is designed according to the signal processing method,which shows that the simulation results are consistent with the theory.Finally,the BeiDou satellite navigation signal simulator was designed and verified.We design the overall architecture of the satellite navigation signal simulator based on the software defined radio platform,implement the data link and satellite channel and detailly state the implementation method of the key unit.Then we verify the implementation by testing the spectrum of the satellite signal simulated and the fading characteristics of the mobile wireless satellite communication channel.Testing by the receiver prove that the satellite signal simulator is able of 5-star simulation with a positioning accuracy of 10m.