Adaptive equalizer

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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[edit]


  1. ^ S. Haykin. (1996). Adaptive Filter Theory. (3rd edition). Prentice Hall.
  2. ^ Tutorial on the LMS algorithm
  3. ^ Decision Feedback Equalizer
  4. ^ Warwick, Colin (March 28, 2012). "For Decision Feedback Equalizers, Beauty is in the Eye". Agilent Technologies. 
  5. ^ Stevens, Ransom. "Equalization: The Correction and Analysis of Degraded Signals" (PDF).