Editing Jitter (section)

{{Short description|Clock deviation from perfect periodicity}}
{{redirect|Wander||Wander (disambiguation)|and|Jitter (disambiguation)}}
{{More citations needed|date=March 2009}}

In [[electronics]] and [[telecommunications]], '''jitter''' is the deviation from true periodicity of a presumably [[periodic signal]], often in relation to a reference [[clock signal]]. In [[clock recovery]] applications it is called '''timing jitter'''.<ref name=wol91p211>{{cite book |last=Wolaver |first=Dan H. |date=1991 |title=Phase-Locked Loop Circuit Design |url=https://archive.org/details/phaselockedloopc00wola |url-access=limited |publisher=Prentice Hall |isbn=978-0-13-662743-2 |page=[https://archive.org/details/phaselockedloopc00wola/page/n215 211]}}</ref> Jitter is a significant, and usually undesired, factor in the design of almost all [[communications link]]s.

Jitter can be quantified in the same terms as all time-varying signals, e.g., [[root mean square]] (RMS), or [[peak-to-peak]] displacement.  Also, like other time-varying signals, jitter can be expressed in terms of [[spectral density]].

'''Jitter period''' is the interval between two times of maximum effect (or minimum effect) of a signal characteristic that varies regularly with time.  '''Jitter frequency''', the more commonly quoted figure, is its inverse. [[ITU-T]] G.810 classifies deviation lower frequencies below 10&nbsp;Hz as '''''wander''''' and higher frequencies at or above 10&nbsp;Hz as ''jitter''.<ref>{{cite web |title=FTB-8080 Sync Analyzer: Resolving Synchronization Problems in Telecom Networks |publisher=EXFO |url=http://documents.exfo.com/appnotes/anote119-ang.pdf |id=Application note 119 |access-date=2012-08-05 |url-status=dead |archive-url=https://web.archive.org/web/20120207103425/http://documents.exfo.com/appnotes/anote119-ang.pdf |archive-date=2012-02-07 }}</ref>

Jitter may be caused by [[electromagnetic interference]] and [[crosstalk]] with carriers of other signals. Jitter can cause a display monitor to flicker, affect the performance of processors in personal computers, introduce clicks or other undesired effects in audio signals, and cause loss of transmitted data between network devices. The amount of tolerable jitter depends on the affected application.