Techniques for high-speed implementation of nonlinear cancellation

The authors present techniques for breaking the bottleneck caused by delays in the feedback loop, which can severely limit the maximum data rate of a detector, operating with nonlinear cancellation (NLC). The authors first show how to simplify the loop to avoid high-speed switching of analog signals by using multiple decision elements, each with a different threshold level. The authors then show how to use lookahead computation to increase the delay permissible in the feedback loop. The authors describe nonlinear cancellation, and outline some of the problems of implementing NLC at high data rates. Techniques for overcoming these problems are developed and are illustrated with the example of a simple one-tap NLC. The authors describe how to generalize the techniques to more complex NLCs and present some more examples.>