Design of Transmitter and Receiver Filters for Decision Feedback Equalization

The advantage of using a nonlinear device, referred to as a decision feedback equalizer, to cancel the tails of pulses whose amplitudes have already been estimated in a PAM system has long been recognized. Figure 1 depicts the typical system in which the decision feedback mechanism has always been envisioned to perform this task. Namely, by making decisions on a symbol-by-symbol basis and by knowing the channel response precisely, a data system would be designed so that postcursor (tails of preceding pulses) ISI could be eliminated without the ambient noise penalty t h a t a linear filter or equalizer imposes. The tacit assumption being made in any decision feedback implementation is that the signal-to-noise ratio is high without 503 TRANSMITTER FILTER FILTER RECEIVER FILTER DECISION FEEDBACK PROCESSOR Fig. 1--Transmitter and receiver filter design.