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IEVref: | 561-03-02 | ID: | |

Language: | en | Status: Standard | |

Term: | Allan variance of fractional frequency fluctuation | ||

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Definition: | unbiased estimate of the preferred definition in the time domain of the short-term stability characteristic of the oscillator output frequency given by $\sigma}_{y}{}^{2}\left(\tau \right)\cong \frac{1}{M\u20131}{\displaystyle \sum _{k=1}^{M\u20131}\frac{{\left({Y}_{k+1}\u2013{Y}_{k}\right)}^{2}}{2}$ where
Note 1 to entry: The confidence of the estimate improves as Note 2 to entry: This entry was numbered 561-04-18 in IEC 60050-561:1991. | ||

Publication date: | 2016-07 | ||

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Replaces: | 561-03-02:2014-11 | ||

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$\sigma}_{y}{}^{2}\left(\tau \right)\cong \frac{1}{M\u20131}{\displaystyle \sum _{k=1}^{M\u20131}\frac{{\left({Y}_{k+1}\u2013{Y}_{k}\right)}^{2}}{2}$

where

*Y*_{k} are the average fractional frequency fluctuations obtained sequentially, with no systematic dead time between measurements;

*τ* is the sample time over which the measurements are averaged;

*M* is the number of measurements

Note 1 to entry: The confidence of the estimate improves as *M* increases.

Note 2 to entry: This entry was numbered 561-04-18 in IEC 60050-561:1991.