Inherently Matched Self-Dual Structures
Speaker:
Rafael Kastner
Professor Emeritus, School of Electrical Engineering, Tel Aviv University & Visiting Professor at the University of Pennsylvania
Abstract
Electric-magnetic homogeneous media obeying the Weston condition are matched to free-space and produce zero backscattering at a planar interface in response to a normally incident plane wave (V. H. Weston, “Theory of Absorbers in Scattering,” IEEE Trans. Antennas Propagat., Vol. 11, No. 5, pp. 578-594, Sept. 1963). In order to facilitate possible realizations, such structures have been approximated by checkerboard-like partitioning of the medium into finite electric-only and magnetic-only regions across the interface (i.e. a checkerboard with alternating electric and magnetic materials). We show that this type of partitioning can be designed to yield a very interesting property: inherently zero backscatter on its own merits and not merely as an approximation to the homogeneous case. For a periodic arrangement whose unit cell is smaller than the wavelength all the incident power is thus transferred across the interface with no reflection. To achieve such this type of matching, the only necessary condition is for the medium to be self-dual for all cross sections parallel to the interface. Self-duality means that the cross section remains unchanged when rotated 900 around the axis of propagation and electric and magnetic regions are interchanged. Cross sections can vary in shape and mutual electric-magnetic orientation, even with abrupt changes. In all these cases, no local reflections are observed, thanks to buildup of local evanescent modes around the interface that support this smooth transition. With specific designs, it is also possible to funnel the energy through very narrow bores when the structure has low losses. Other applications are in the areas of phased array design and thin absorbers.
About the Speaker
Raphael Kastner received the B.Sc. (summa cum laude) and the M.Sc. degrees in electrical engineering from the Technion, Israel Institute of Technology in 1973 and 1976, respectively, and his Ph.D. degree from the University of Illinois, Urbana, in 1982.
From 1976 to 1988 he was with RAFAEL, Israel Armament Development Authority, where from 1982 to 1986 he headed the antenna section. He was a Visiting Assistant Professor at Syracuse University from 1986 to 1987, and a Visiting Scholar at the University of Illinois in 1987 and 1989. Since 1988 he has been with the School of Electrical Engineering, Tel Aviv University, where is now a Professor Emeritus. In 2000 he co-founded XellAnt Inc. and acted as its CEO until 2004. He is a Life Fellow, a recipient of the IEEE Third Millenium medal and several excellence in teaching awards, and a member of Tau Beta Pi and Eta Kappa Nu. His research interests are in computational electromagnetics and antennas. Since January 2016, he has been Visiting Professor at the University of Pennsylvania.