Theory on negative time-delay looped system

An innovative theory on the looped system generating negative time delay is presented. Both the direct and delayed feedback loop topologies of this system essentially consist of an independent-frequency gain and time-delay block. It is shown theoretically that for suitable parameters the system can generate a negative time delay by virtue of a negative group delay (NGD). Analytical expressions reveal that the system presents an unconditional low-pass NGD behaviour. The NGD properties as a function of the system parameters are derived. To demonstrate the feasibility of the developed NGD system concept, frequency- and time-domain analyses are performed with Matlab, resulting in a very good agreement between the simulations and theory. Furthermore, as illustrated by computational results, negative time-delay signal propagation (signal advance) is obtained. The proposed NGD system can potentially be useful for time-delay compensation in engineering systems.