Negative Group Delay in Microstrip/Negative-Refractive-Index Couplers Supporting Complex Modes

Hassan Mirzaei

The Edward S. Rogers Sr. Department of Electrical and Computer Engineering (Electromagnetics)

Abstract:

The observation of negative group delay (NGD) is an interesting phenomenon since it seems to imply traveling 'backwards' in time. In a circuit with NGD the peak of a pulse exits the circuit before its peak enters that circuit. However, it is well understood that this counterintuitive phenomenon does not violate the Einstein's causality. We demonstrate a new circuit in which the coupling between a positive-index transmission line (a microstrip line) and a negative-index transmission line (a microstrip line loaded with series capacitors and shunt inductors) results in a NGD. The circuit's frequency-domain and time-domain experimental results will be demonstrated. The modification of this circuit to one with constant phase-shift will be presented along with corresponding experimental results. We will also discuss an optical analogue of this NGD circuit in the form of a plasmonic coupler. NGD circuits are usually accompanied by large resistive loss. This circuit is unique in that the lines do not contain any resistive loading and could ideally be lossless.

Biography:

Hassan Mirzaei obtained his B.Sc. degree in Electrical and Computer Engineering (Electronics) from Isfahan University of Technology, Iran and his M.Sc. degree in Electrical Engineering (Optical and Microwave Communication) from Sharif University of Technology, Iran. After graduation, he worked as a microwave engineer at several iranian telecommunication companies where he was involved in the design of microwave circuit and systems. From 2007 to 2008, he was a research assistant at the University of Waterloo. He is currently working toward his PhD degree at the University of Toronto under the supervision of Professor Eleftheriades. His research interests are dispersion engineering and application of wave propagation and interaction theory to high performance circuit design.