Studies On Group Delay And Signal Fidelity In Negative Group Delay Circuits

The study of the superluminal phenomenon has lasted for more than half a century,There are two main ways to achieve this phenomenon.One is the optical regulation in anomalous dispersion medium;the other is the use of electronic circuits to construct anomalous dispersion regions to achieve the superluminal phenomenon.The latter was observed by Chiao et al in 1997.When the pulse passes through the negative delay time,and the signal has been advanced.First,we experimentally show that the fidelity of pulses can be manipulated by controlling the phase and gain of a dual-band electronic amplifier applied to a cascaded electronic circuit system.The cascaded response of two negative group delay(NGD)systems operating at different center frequencies is also presented in order to obtain broader NGD bandwidth.NGDs with linear phase characteristics at the operating frequencies are also designed and experimentally verified.Then,we consider three cases:First,a smooth Gaussian envelope modulated sine wave,which is a complete signal.Second,a truncated Gaussian envelope modulated sine wave,which can be set at different truncation parameters.Third,a smooth compact support(SCS)envelope modulated sine wave.It shows that high-fidelity can be determined by the maximal effective region in the NGD.Furthermore,different truncation parameters of pulses also affect the fidelity of pulses in such a dual-band RLC amplifier.Our result provides a method to define the integrity on the pulse propagation inside the dispersive media.