Research On Hardware Delay Measurement Method Of BDS-3 Time And Frequency Transfer Equipment

With the opening of the global satellite navigation and positioning system of BDS-3,Chinese satellite navigation and positioning system has entered a new stage of development,and the domestic time users’ demand for high-precision time has also increased.Time and frequency transfer is the way for users to obtain precise and accurate time and frequency.However,the high calibration uncertainty of GNSS time and frequency transfer link is the main factor restricting the current high-precision time and frequency transfer.In GNSS time and frequency transfer link calibration,the main calibration object is the hardware delay of time and frequency transfer equipment(receiver).At present,most of the relevant research is based on the American GPS system,and there is little research on Chinese BDS system.Therefore,the research on the calibration method of time and frequency transfer receiver based on the latest BDS-3 global system is of great significance for the research itself and the application of independent and controllable satellite navigation in relevant industries in China in the future.Based on the comprehensive analysis of the influence of BDS-3 time and frequency transfer equipment calibration performance,calibration methods and theories,this thesis puts forward the idea of absolute overall calibration,and obtains the optimal method of BDS-3 time and frequency transfer equipment absolute calibration through the comparative experiment and verification test of different calibration methods.The research contents of this thesis mainly include:1.According to the precise calibration requirements of BDS-3 time and frequency transfer link,the GNSS time and frequency transfer method and PID clock taming control algorithm are studied.A set of GNSS time synchronization performance analysis software is developed through simulation,and the influence of the calibration performance(uncertainty)of BDS-3 time and frequency transfer equipment on the time synchronization performance is analyzed.2.The hardware delay calibration scheme of BDS-3 time and frequency transfer equipment is designed,and the absolute calibration system of BDS-3 time and frequency transfer equipment is developed.For the calibration of BDS-3 signal simulator in absolute calibration,a method based on digital modulation signal demodulation post-processing is proposed,and the calibration of signal simulator is realized by restoring the original baseband digital signal;On the basis of step-by-step absolute calibration,an overall absolute calibration scheme is proposed to realize the hardware delay calibration under the overall operation state of time and frequency transfer equipment.The transmitting antenna calibration method based on the comparison and processing of pseudo range observation data in different simulation scenarios has great reference value for the calibration of receiving antenna in step-by-step absolute calibration.The overall absolute calibration method avoids the tedious step-by-step absolute calibration steps,avoids the introduction of more uncertainty,and the calibration is completely based on the simulated BDS-3satellite signal,making the calibration method more standard,the scene environment more consistent,and the results more accurate and reliable.3.Based on the BDS-3 time and frequency transfer equipment absolute calibration system,an absolute calibration experiment verification platform is jointly constructed.Through the experiments of different calibration methods,the reliability of calibration methods and the accuracy of calibration results are mutually verified.By comparing the uncertainty evaluated by each method and the characteristics of application scenarios,It is concluded that the overall absolute calibration method of hardware delay of BDS-3 time and frequency transfer equipment has lower uncertainty and simpler calibration steps than the step-by-step absolute calibration method;The absolute calibration method of hardware delay of BDS-3 time and frequency transfer equipment is poor.The calibration method has stronger recyclability and can complete the calibration in the local laboratory without relying on the reference time and frequency transfer equipment;Therefore,the reference BDS-3 time and frequency transfer equipment can be formed in the local laboratory through overall absolute calibration,and then a wide range of calibration applications can be carried out through differential calibration.