An Algorithm for Real-Time Sub-Nanosecond Level Time Synchronization Based on RTK Timing Inverse Correction and Kalman Filtering

Abstract

This article proposes a new algorithm for real-time sub-nanosecond level time synchronization based on GNSS RTK technique and the Kalman Filtering. It is able to improve the performance of time synchronization system as well as a sub-nanosecond level, with a real time response. Although the IGS products theoretically improve the accuracy up to a sub-nanosecond or even higher level, the weakness of more pool performance in a shorter duration and of a lower update rate make us scarcely possibly get an accurate timekeeping upper than nanosecond level only relying on the IGS products. The RTK TIC algorithm uses the RTK position results of (xrtk, yrtk, zrtk) to inversely and iteratively update the time keeping results from pseudorange PVT equations to a high level accuracy. Meanwhile, in order to suppress the error coming from ephemeris change, the FS725 Stanford Rubidium Atomic Clock are used as a compensation equipment for coupling the GNSS timekeeping results via the Kalman Filtering. Then, this paper gives the validation of the RTK TIC algorithm with a two-channel system and compares mean values and standard deviations between our system and two SYN4505As, the results shows our system has a better timekeeping accuracy than the SYN4505As. At last, this paper calibratesthe accuracy of our system via the standard clock source in the NTCS, and gives the results that our system has an excellent performance on the real-time sub-nanosecond level time synchronization.