A backward time shift filter for nonlinear delayed-feedback systems

Using a simple nonlinear filter, it is possible to shift arbitrarily comple x wave forms produced by systems with a delayed feedback backwards in time. Physically, this corresponds to a seemingly noncausal transmission of sign als. Filter chains allow for signals travelling against the coupling direct ion of the chain. These apparent paradoxes are resolved and possible physic al implications are discussed. (C) 2001 Elsevier Science B.V. All rights re served.