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Panfilo G.,International Bureau for Weights and Measures BIPM | Parker T.E.,U.S. National Institute of Standards and Technology

Results are presented from a theoretical and experimental investigation of the frequency transfer uncertainty (FTU) in long-distance comparisons of frequency standards. The FTU can be an important component of the total uncertainty in such comparisons. The use of the Allan deviation in characterizing the FTU is analysed theoretically and it is shown that for certain noise types the Allan deviation is biased high. A potentially more accurate first difference statistic that can be used in certain situations is also discussed. In addition, an experimental determination of the noise types and levels in common transfer techniques is presented. It is shown that FTUs approaching 1 part in 1016at 30 days are possible with current transfer methods. Finally, a method is presented for estimating the FTU in calibrating International Atomic Time (TAI) with a primary frequency standard. © 2010 BIPM & IOP Publishing Ltd. Source

Panfilo G.,International Bureau for Weights and Measures BIPM | Arias E.F.,International Bureau for Weights and Measures BIPM
IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control

This article reviews the creation and technical evolution of atomic time scales. In particular, we focus our attention on the method of calculation and the characteristics of International Atomic Time (TAI), and show how it is disseminated at the ultimate level of precision. © 2006 IEEE. Source

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