Research On GNSS High Precision Timing Receiver Based On PPP Technology

Infrastructure in the areas of communications,electric power,finance,and national defense is built on time synchronization.The time synchronization requirements of the state of art applications are more and more accurate.The time synchronization accuracy of the time comparison using GNSS(Global Navigation Satellite System)can reach nanoseconds,but usually only several nodes can be performed,and the comparison result has hysteresis.This kind of technology is mainly used by the timing laboratories,and is not suitable for a wide range of uses.The use of satellite navigation systems for timing to achieve time synchronization has the advantages of low cost,real-time,unlimited number of users and global coverage.However,the current use of satellite navigation systems for timing accuracy is generally above 15 ns,which has gradually unable to meet the growing demand for high-precision time synchronization.China's Beidou satellite navigation system has now developed to the third generation,and will soon be able to provide positioning and timing services globally.With the construction completed of China's ground-based augmentation system and the maturity of high-precision positioning technology,real-time centimeter-level positioning(Shi C et al.2017)is now available.The positioning accuracy improves quickly while timing accuracy remains unchanged.To this end,we design a timing receiver based on wide-area precision positioning technology for the current high-precision timing using satellite navigation system,and studies its key technologies,including:1.The hardware architecture of the timing receiver based on precise point positioning technology is designed.Current research on accurate calibration of hardware delays is mostly based on time comparison receivers.Based on the analysis of the timing signal output process and the derivative timing error of the timing receiver,we present a hardware delay calibration method based on clock error compensation.The calibration experiment of the timing receiver is carried out.Finally,the uncertainty analysis of the accuracy of the calibration method is given.2.To perform high-precision timing,you must first accurately model the clock used,and modeling the clock requires the frequency stability of the clock.For the current situation of high-cost frequency reference source and precision instrument for frequency measurement,this paper proposes that the precision single-point positioning technology can be used to measure the clock frequency stability,which has the advantages of low cost and high precision.In this paper,an OCXO(Oven Controlled Crystal Oscillator)and a rubidium atomic clock are evaluated by this method,and the results are analyzed.The frequency stability evaluation ability of precise single point positioning technology is given.3.Current research on accurate calibration of hardware delays is mostly based on time comparison receivers.Based on the analysis of the timing signal output process and the derivative timing error of the timing receiver,we present a hardware delay calibration method based on clock error compensation.The calibration experiment of the timing receiver is carried out.Finally,the uncertainty analysis of the accuracy of the calibration method is given.Based on the above key technologies,a simulation program was designed to study the clock state estimation and the clock steering.Besides,we designed a high-precision timing receiver based on PPP for final verification.After completing the clock frequency stability evaluation and hardware delay calibration,we conducted a two-receiver comparison test.And then,we evaluated the wide-area timing performance of the timing receiver based on precision positioning technology at the National Time Service Center.The 1 PPS output stability is less than 1 ns/day,the frequency stability is about 2×10^-14/day.