Considerations on the measurement of the stability of oscillators with frequency counters

S.T. Dawkins, John Mcferran, Andre Luiten

Research output: Contribution to journalArticlepeer-review

176 Citations (Scopus)


The most common time-domain measure of frequency stability, the Allan variance, is typically estimated using 43, frequency counter. Close examination of the operation of modern high-resolution frequency counters shows that they do not make measurements in the way commonly assumed. The consequence is that the results typically reported by many laboratories using these counters are not, in fact, the Allan variance, but a distorted representation. We elucidate the action of these counters by consideration of their operation in the Fourier domain, and demonstrate that the difference between the actual Allan variance and that delivered by these counters can be very significant for some types of oscillators. We also discuss ways to a:void, or account for, a distorted estimation of Allan variance.
Original languageEnglish
Pages (from-to)918-925
JournalIEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
Issue number5
Publication statusPublished - 2007


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