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IEVref:561-03-02ID:
Language:enStatus: 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

σ y 2 ( τ ) 1 M1 k=1 M1 ( Y k+1 Y k ) 2 2 MathType@MTEF@5@5@+=feaagCart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLnhiov2DGi1BTfMBaeXatLxBI9gBaerbbjxAHXgarqqtubsr4rNCHbGeaGqipG0dh9qqWrVepG0dbbL8F4rqqrVepeea0xe9LqFf0xc9q8qqaqFn0lXdHiVcFbIOFHK8Feea0dXdar=Jb9hs0dXdHuk9fr=xfr=xfrpeWZqaaeqabiGaciGacaqadmaadaqaaqaaaOqaaiabeo8aZnaaBaaaleaacaWG5baabeaakmaaCaaaleqabaGaaGOmaaaakmaabmaabaGaeqiXdqhacaGLOaGaayzkaaGaeyyrIa0aaSaaaeaacaaIXaaabaGaamytaiaacobicaaIXaaaamaaqahabaWaaSaaaeaadaqadaqaaiaadMfadaWgaaWcbaGaam4AaiabgUcaRiaaigdaaeqaaOGaai4eGiaadMfadaWgaaWcbaGaam4AaaqabaaakiaawIcacaGLPaaadaahaaWcbeqaaiaaikdaaaaakeaacaaIYaaaaaWcbaGaam4Aaiabg2da9iaaigdaaeaacaWGnbGaai4eGiaaigdaa0GaeyyeIuoaaaa@51A1@

where

Yk 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.


Publication date:2016-07
Source:
Replaces:561-03-02:2014-11
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