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An '''adaptive equalizer''' is an [[equalizer (communications)|equalizer]] that automatically adapts to time-varying properties of the [[communication channel]].<ref>S. Haykin. (1996). Adaptive Filter Theory. (3rd edition). Prentice Hall.</ref> It is frequently used with coherent modulations such as [[phase shift keying]], mitigating the effects of [[multipath propagation]] and [[Fading|Doppler spreading]]. | |||
Many adaptation strategies exist. They include: | |||
*[[Least mean squares filter|LMS]] Note that the receiver does not have access to the transmitted signal <math>x</math> when it is not in training mode. If the probability that the equalizer makes a mistake is sufficiently small, the symbol decisions <math>d(n)</math> made by the equalizer may be substituted for <math>x</math>.<ref>[http://cnx.org/content/m10481/latest/ Tutorial on the LMS algorithm]</ref> | |||
*[[Recursive least squares filter|RLS]] | |||
A well-known example is the [[decision feedback equalizer]],<ref>[http://cnx.org/content/m15524/latest/ Decision Feedback Equalizer]</ref><ref>{{cite web | url = http://signal-integrity.tm.agilent.com/2012/decision-feedback-equalizer-beauty-is-in-the-eye/ | title = For Decision Feedback Equalizers, Beauty is in the Eye | first = Colin | last = Warwick | date = March 28, 2012 | publisher = Agilent Technologies }}</ref> a filter that uses feedback of detected [[Modulation|symbols]] in addition to conventional equalization of future symbols.<ref>{{cite web | |||
| url = http://cp.literature.agilent.com/litweb/pdf/5989-3777EN.pdf | |||
| title = Equalization: The Correction and Analysis of Degraded Signals | |||
| first = Ransom | |||
| last = Stevens | |||
}}</ref> Some systems use predefined training sequences to provide reference points for the adaptation process. | |||
==See also== | |||
* [[Equalizer (communications)|Equalizer]] | |||
* [[Intersymbol interference]] | |||
== References == | |||
<references/> | |||
{{DEFAULTSORT:Adaptive Equalizer}} | |||
[[Category:Data transmission]] | |||
[[Category:Digital signal processing]] |
Revision as of 09:42, 26 February 2013
An adaptive equalizer is an equalizer that automatically adapts to time-varying properties of the communication channel.[1] It is frequently used with coherent modulations such as phase shift keying, mitigating the effects of multipath propagation and Doppler spreading.
Many adaptation strategies exist. They include:
- LMS Note that the receiver does not have access to the transmitted signal when it is not in training mode. If the probability that the equalizer makes a mistake is sufficiently small, the symbol decisions made by the equalizer may be substituted for .[2]
- RLS
A well-known example is the decision feedback equalizer,[3][4] a filter that uses feedback of detected symbols in addition to conventional equalization of future symbols.[5] Some systems use predefined training sequences to provide reference points for the adaptation process.
See also
References
- ↑ S. Haykin. (1996). Adaptive Filter Theory. (3rd edition). Prentice Hall.
- ↑ Tutorial on the LMS algorithm
- ↑ Decision Feedback Equalizer
- ↑ Template:Cite web
- ↑ Template:Cite web