Antennas and Wireless Propagation Letters Special Edition Guest Editors

Professor David Smith and Professor Steve Cummer (an affiliate for the Center for Metamaterials and Integrated Plasmonics and a Faculty member of Electrical and Computer Engineering at Duke University) both have articles appearing in a special cluster issue on metamaterials in 'Antennas and Wireless Propagation Letters by IEEE'. D.R. Smith also served as a guest editor for the 2011 edition, which consists of over 30 papers devoted to metamaterials. The special cluster issue is a first for AWPL.

The papers in this special cluster collectively represent a snapshot of many of the research directions currently underway in the metamaterials community and are illustrative of the potential that can be unlocked by simply taking a broader view of what constitutes a "material." Guest Editorial co-authored by David Smith and former CMIP member David Schurig can found on page 1476 "Special Cluster on Metamaterials" focuses on the metamaterial concept as a whole. Metamaterials have captured the imagination of a significant and growing pool of researchers from a wide range of fields, with the move toward practical applications perhaps most evident in the area of antennas and wireless propagation. The idea of using collections of sub-wavelength elements in a structured medium of three dimensions (volumetric metamaterials), two dimensions (meta-surfaces) and even one dimension (meta-wires) provides unprecedented control over medium properties. These mediums can have exotic properties, previously inaccessible, or common properties with uncommon control over spatial variation, polarization sensitivity and frequency dispersion. This expansion of the available parameter space of mediums has spurred engineers to reevaluate existing performance trade-offs and propose new devices. The impact on antennas and propagation includes: high impedance ground planes, engineered reflectance, matching and bandwidth enhancement, multiple-antennainterference reduction, compact resonators, transparent media and low aberration (high gain) refractive elements. In addition, resonator designs initially created for metamaterials have often been used singly or in small groups, as their characteristics became well understood and were found to be favorable. Analysis techniques, numerical methods and experimental characterization methods developed n metamaterial research have also migrated to engineering work not strictly incorporating metamaterials.

On page 1605 "Analysis of Gradient Index Metamaterials Blazed Diffraction Grating" addresses the equivalent of a blazed diffraction grating can be formed from an array of metamaterial elements arranged so as to produce a linear gradient in the effective refractive index. By spreading the gradient over a multiwavelength distance, and repeating the pattern many times, a gradient index (GRIN) diffraction grating is formed. Using lithographically patterned, metallic metamaterial elements, dozens of distinguishable phase levels can be implemented by slightly modifying the design of each successive metamaterial element.We analyze here a multilayer metamaterial diffraction grating designed for operation at 10.6 m, exploring the impact of material losses and impedance mismatch on the diffraction efficiency.

"RF Limiter Metamaterial Using p-i-n Diodes" Authored by: Alexander R. Katko, Student Member, IEEE, Allen M. Hawkes, John P. Barrett, Student Member, IEEE, and Steven A. Cummer, Fellow, IEEE. On page 1571, this paper presents the design and experimental implementation of an RF limiter metamaterial using a sheet of nonlinear metamaterials. We demonstrate that complementary electric inductive- capacitive resonators loaded with nonlinear p-i-n diodes can act as RF limiter unit cells. We design and fabricate limiter metamaterials and compare them to traditional circuit limiters. Our limiter metamaterial exhibits a minimum insertion loss under 3 dB, a maximum decrease in transmission of 6.95 dB and broadband performance, with a minimum decrease in transmission of 3 dB over 18% bandwidth. The limiter metamaterial is suitable for a wide variety of practical applications requiring protection of sensitive devices from high power.

IEEE ANTENNAS AND WIRELESS PROPAGATION LETTERS is published annually by The Institute of Electrical and Electronics Engineers, Inc.