A design and implementation of disciplined clock based on GNSS

 ZHANG Fan^1,2,3, HU Yong-hui^1,2, HE Zai-min^1,2,3

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

2. Key Laboratory of Precision Navigation and Timing Technology, National Time Service Center,

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

3. Graduate University of Chinese Academy of Sciences, Beijing 100039, China

Abstract: The software design for a disciplined clock based on GNSS is introduced emphatically. In the design of software, a moving median filter is adopted to remove the wild-values, the Kalman filter is used to filter the measurement noise in time-difference data, and an improved method of obtaining the control-voltage is proposed. The frequency accuracy of a constant temperature crystal oscillator with an original accuracy of 1×10-9 is better than 2×10-11 after it is disciplined with the 1 PPS of GPS timing receiver as reference standard.

Key words: disciplined clock; moving median filter; Kalman filter