%0 Journal Article
%T Recent Advances in Multiband Printed Antennas Based on Metamaterial Loading
%A F. Paredes
%A G. Zamora
%A S. Zufanelli
%A F. J. Herraiz-Mart¨ªnez
%A J. Bonache
%A F. Mart¨ªn
%J Advances in OptoElectronics
%D 2012
%I Hindawi Publishing Corporation
%R 10.1155/2012/968780
%X It is shown that printed antennas loaded with metamaterial resonators can be designed to exhibit multiband functionality. Two different antenna types and metamaterial loading are considered: (i) printed dipoles or monopoles loaded with open complementary split ring resonators (OCSRRs) and (ii) meander line or folded dipole antennas loaded with split ring resonators (SRRs) or spiral resonators (SRs). In the first case, multiband operation is achieved by series connecting one or more OCSRRs within the dipole/monopole. Such resonators force opens at their positions, and by locating them at a quarter wavelength (at the required operating frequencies) from the feeding point, it is possible to achieve multiple radiation bands. In the second case, dual-band functionality is achieved through the perturbation of the antenna characteristics caused by the presence of the metamaterial resonators. This latter strategy is specially suited to achieve conjugate matching between the antenna and the chip in radiofrequency identification (RFID) tags at two of the regulated UHF-RFID bands. 1. Introduction Metamaterials are effective media made of periodic (or quasiperiodic) inclusions of conventional materials (typically metals and dielectrics) with controllable acoustic, electromagnetic, or optical properties. Indeed, by properly structuring these artificial materials, it is possible to achieve unique and exotic properties, such as negative refraction or subwavelength focusing, among others, and it is potentially possible to implement acoustic and optical cloaks. There has been an intensive research activity in this field since 2000 [1¨C10], when the first metamaterial structure by Smith and co-workers was reported [11]. Key to the success of this research field was the synthesis of negative effective permeability media by means of split ring resonators (SRRs) [12]. These particles are electrically small resonators that can be excited by means of an axial magnetic field. Hence, if an array of SRRs is illuminated by means of an electromagnetic radiation with the magnetic field axial to the SRRs, the structure behaves as an effective medium with negative permeability in a narrow band above SRR resonance. By combining SRRs with metallic posts (exhibiting a negative effective permittivity up to the so-called plasma frequency), the first structure simultaneously exhibiting negative permittivity and permeability was synthesized [11]. These structures are called left-handed, or double negative, materials, and the main relevant feature of such media, derived from the negative sign
%U http://www.hindawi.com/journals/aoe/2012/968780/