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http://dx.doi.org/10.11003/JPNT.2020.9.3.261

Kalman Filter-Based Ensemble Timescale with 3- Hydrogen Masers  

Lee, Ho Seong (Time and Frequency Group, Korea Research Institute of Standards and Science)
Kwon, Taeg Yong (Time and Frequency Group, Korea Research Institute of Standards and Science)
Lee, Young Kyu (Time and Frequency Group, Korea Research Institute of Standards and Science)
Yang, Sung-hoon (Time and Frequency Group, Korea Research Institute of Standards and Science)
Yu, Dai-Hyuk (Time and Frequency Group, Korea Research Institute of Standards and Science)
Publication Information
Journal of Positioning, Navigation, and Timing / v.9, no.3, 2020 , pp. 261-272 More about this Journal
Abstract
A Kalman filter algorithm is used for the generation of an ensemble timescale with three hydrogen masers maintained in KRISS. Allan deviation curves of three pairs of clocks were obtained by a three-cornered hat method and were used as reference curves for determination of parameters of the Kalman filter-based timescale. The ensemble timescale equation of a 3-clock system was established, and the clocks' phases estimated by the Kalman filter were used as the prediction time of each clock in the equation. The weight of each clock was determined inversely proportional to the Allan variance calculated with the clocks' phases. The Allan deviation of the weighted mean was 1.2×10-16 at the averaging time of 57,600 s. However when we made fine adjustments of the clocks' weight, the minimum Allan deviation of 2×10-17 was obtained. To find out the reason of the great improvement in the frequency stability, additional researches are in progress theoretically and experimentally.
Keywords
Kalman filter; timescale; ensemble clock; Allan deviation; hydrogen masers;
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