Holdover in synchronization applications: Difference between revisions

Revision as of 01:13, 25 December 2012

Revision as of 18:10, 6 March 2013

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In a GPSDO a GPS or GNSS signal is used as the exernalexternal reference that steers an internal oscillator.<ref name="autogenerated3"/> In a modern GPSDO the GPS processing and steering function are both implemented in a Microprocessor allowing a direct comparison between the GPS reference signal and the oscillator output.<ref name="timing1"/>

[[File:GPSDO.png|thumb|left|A Modern [[GPSDO]]]]

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Once the barriers of aging and environmental effects are removed the only theoretical limitation to holdover performance in such a GPSDO is irregularity or noise in the drift rate, which is quantified using a metric like [[Allan deviation]] or [[Time deviation]].<ref>http://www.leapsecond.com/pages/adev/adev-why.htm</ref>{{Unreliable source?|date=October 2012}}

The complexity in trying to predict the effects on Holdover due to systematic effects like Agingaging and TemperatureTtmperature Stabilitystability and stochastic influences like [[Random walk|Random Walk]] noise has resulted in tailor -made ''Holdover Oscillator'' solutions being introduced in the market.<ref>{{cite web|url=http://www.vectron.com/products/modules/MD-023.pdf |title=MD-023: Extended Holdover Crystal Oscillator |publisher=Vectron International |date=June 2011 |accessdate=2012-10-21}}</ref>

==See also==