ZHANG Fan1,2,3, HU Yong-hui1,2, HE Zai-min1,2,3
(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
