LU Jian-fu^1,2, GAO Yu-ping^1,3, LIN Si-jia^1,2, LIU Biao^1,2

(1. National Time Service Centre, Chinese Academy of Sciences, Xi′an 710600, China;

2. University of Chinese Academy of Sciences, Beijing 100039, China;

3. Key Laboratory of Time and Frequency Primary Standards, National Time Service Center,

Chinese Academy of Sciences, Xi′an 710600, China)

Abstract: In order to ensure the accuracy and stability of time signal in switching the primary and backup clock, we studied the methods of maintaining consistency between the primary and backup clock and built an experiment system to maintain the consistency between the primary and backup clock. In this paper, the principle of the system is demonstrated, the results of different clock offset prediction models are analyzed, and the formula of frequency compensation for backup clock is given. The levels of synchronization for different control cycles are tested and the tests show that by using the method described here the time difference between the primary and backup clock is less than 1 ns as well as the long-term frequency stability of the output signal of the backup clock can be improved.