Wave-Interference Explanation of Group-Delay Dispersion in Resonators [Education Column]

This paper presents a rigorous and intuitive wave-interference explanation of group-delay dispersion in resonators. It considers both one-port and two-port lossless and lossy resonators under the complementary frequency-domain and time-domain perspectives. The reasons for the group-delay dispersive nature of a resonator and for the phenomenon of negative group delay (superluminality) in a lossy resonator are clearly explained in terms of the constructive and destructive interferences of multiply reflected pulses.