This book presents an innovative theory of active circuit topologies exhibiting the negative group delay (NGD) function appli. in RF/electronic engineering. The basic properties of this abnormal function are established. An analogy between the NGD behaviour and filter gain is developed. Then, several elementary cells operating as low-pass, high-pass, band-pass and stop-band circuits are identified. Then, simulation and experimental results in very good agreement with the theory are offered. Design techniques of NGD low-pass and band-pass proof of concepts respectively operating with super ultra-wide band (UWB) RF signals are described. It is demonstrated theoretically and experimentally that the NGD circuits enable to realize the propagation of limited bandwidth signals with negative time-delay and applications for pure delay cancellation. In other words, the possibility of certain signal wave forms anticipation was verified in theory, simulation and practice. The feasibility of the NDG multiband devices implementation and digital FIR/IIR circuits is presented. Novel topologies of distributed circuits potentially integrable and susceptible to operate up to tens GHz are examined.