Jpn. J. Appl. Phys. 47 (2008) pp. 2294-2299 |Previous Article| |Next Article| |Table of Contents|
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Improvement of Rate Shift in Average Atomic Time Scale Algorithm
Space-Time Standard Group, New Generation Network Research Center, National Institute of Information and Communications Technology, Koganei, Tokyo 184-8795, Japan
(Received October 13, 2007; accepted December 15, 2007; published online April 18, 2008)
In an average atomic time scale algorithm, we developed a new method of suppressing the influence of a large sudden rate shift in some clocks. The method entails two points. One is to add a clock rate check process. The weight of a bad clock is forced to be zero if its latest rate largely changes from the past rate. The other is to change the weighting itself of clocks. Inversely proportional weighting to the square of Allan deviation, which is thought to be one of the standard methods, turned out to occasionally make the time scale instable, by emphasizing inadequate clocks. We adopted two other loose weightings, namely, even weighting and inverse proportional weighting to Allan deviation. We tested the above two steps by simulation with 16 Cs atomic clocks at the National Institute of Information and Communication Technology (NICT), and showed a successful improvement in the stability of the standard algorithm of the average atomic time scale.
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