The term photonic crystals appears because of the analogy between electron waves in crystals and the light waves in artificial periodic dielectric structures. During the recent years the investigation of one-, two-and three-dimensional periodic structures has attracted a widespread attention of the world optics community because of great potentiality of such structures in advanced applied optical fields. The interest in periodic structures has been stimulated by the fast development of semiconductor technology that now allows the fabrication of artificial structures, whose period is comparable with the wavelength of light in the visible and infrared ranges.

http://ieeexplore.ieee.org/iel5/6354/16969/00781867.pdf

Photonic crystals

Preface 1. Introduction 2. FDTD Method for periodic structure analysis 3. EBG Characterizations and classifications 4. Design and optimizations of EBG structures 5. Patch antennas with EBG structures 6. Low profile wire antennas on EBG surfaces 7. Surface wave antennas Appendix: EBG literature review.

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Electromagnetic Band Gap Structures in Antenna Engineering

Several solutions are presented to reduce the mutual coupling between two planar inverted-F antennas (PIFAs) working in close radiocommunication standards and positioned on a finite-sized ground plane modeling the printed circuit board (PCB) of a typical mobile phone. First, the two PIFAs are designed on separate PCBs to, respectively, operate in the DCS1800 and UMTS bands. In a second step, they are associated on the top edge of the same PCB. Realistic arrangements are then theoretically and experimentally studied. Finally, several solutions are investigated to maximize the isolation. They consist in inserting a suspended line between the PIFAs' feedings and/or shorting points. All along this paper, several prototypes are fabricated and their performances measured to validate the obtained IE3D moment method-based simulation results

Study and Reduction of the Mutual Coupling Between Two Mobile Phone PIFAs Operating in the DCS1800 and UMTS Bands

This review aims to summarise the progress in some materials and structures for electromagnetic applications, such as microwave absorption, electric shielding and antenna designs, which have been developed in recent years. Composites with spherical powders for microwave absorption focus mainly on those based on ferrites (especially hexagonal), carbonyl iron and related alloys and various newly emerged nanosized materials. Composites with long conductive fibres as fillers will be summarised, with speical attentions to prediction, measurment and evaluation of their performances. Metamaterials include structures for microwave absorbing applications, tunable materials or structures with reflection or transmission coefficients that are tunable by external magnetic or electric fields, and specially designed structures for microwave absorbing applications, with thickness much smaller than that of conventional composite materials and performances that can be optimised by the physical properties of substra...

Recent progress in some composite materials and structures for specific electromagnetic applications

We present the design of miniaturized resonant inclusions to be employed in the practical realization of metamaterial samples with anomalous values of the real part of the permeability. Such inclusions, in fact, can be employed in the design of both mu-negative (MNG) materials and artificial magnetodielectrics (with negative and high-positive values of the real part of the permeability, respectively). The inclusions here considered are the multiple split-ring resonators (MSRRs), that represent a straightforward extension of the commonly used split-ring resonators (SRRs), and the spiral resonators (SRs), that enable a greater miniaturization rate. Some physical insights on the resonance mechanism and on the inherent saturation of the resonant frequency when increasing the number of the rings of the MSRRs and the number of the turns of the SRs are given in the paper. New and accurate analytical design formulas, based on a quasi-static model, for both MSRRs and SRs are derived and tested through a proper comparison with the existing formulas and full-wave numerical results. Both MSRRs and SRs are shown to be useful to reduce the electrical dimensions of the resonant inclusions when synthesizing artificial metamaterials.

Design of Spiral and Multiple Split-Ring Resonators for the Realization of Miniaturized Metamaterial Samples

Magnetic properties were imparted to a naturally nonmagnetic material by metallic inclusions. A patch antenna tested the performance of the magnetic metamaterial as a substrate and validated that a single substrate can achieve a range of miniaturization values. The effective medium metamaterial substrate employed electromagnetically small embedded circuits (ECs) to achieve permeability and permittivity greater than that of the host dielectric. Geometric control of the ECs allowed mu and epsi to be tailored to the application. The magnetic metamaterial exhibited enhanced mu and epsi with acceptable loss-factor levels. Models for predicting mu and epsi are presented, the benefits of employing metamaterial substrates are discussed, and the results in this antenna experiment are presented. The metamaterial exhibits performance characteristics not achievable from natural materials. Of particular significance is that with the permeability varying strongly and predictably with frequency, the miniaturization factor may be selected by tuning the operating frequency. Simulations indicate that such performance can be extended to several gigahertz with current technology. Relative permeability values in the mur=1-5 range are achievable for moderately low-loss applications. Representative antenna miniaturization factors on the order of 4-7 over a moderate (approximately 10%) transmission bandwidth and efficiencies in a moderate range (20%-35%) are demonstrated with the possibility of higher efficiencies indicated

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A substrate for small patch antennas providing tunable miniaturization factors

Metamaterial EM insulators are shown to suppress mutual coupling between densely packed array elements. This technique allows for array element design in isolation, without consideration of adjacent elements and mutual coupling effects. Suppressing mutual coupling allows for denser packing and enhanced directivity in antenna arrays approaching the superdirective theoretical maximums. Metamaterial isolation walls 0.05lambda0 thick exhibit 20 dB peak isolations with 10 dB isolation bandwidths of 2-6% and very low losses. These insulators achieve lower than -30 dB coupling levels for 0.2lambda0 periodicity arrays. A simulated 1.18lambda0 five element broadside array exhibits a superdirective 65 degree first-null beamwidth with -9.5 dB side-lobes and when physically fabricated, experiment validates theory with a squinted 75 degree first-null beamwidth and only slight degradation of sidelobe levels. The main beam of the metamaterial insulated array is steerable over a full +/-90 degree horizon with little scan loss and no instances of scan blindness, a null can be placed to any angle including broadside, and as narrow as 25 degree peak-to-null separation is possible

Metamaterial Insulator Enabled Superdirective Array

Magnetic permeability was imparted to a naturally non-magnetic material by metallic inclusions. A patch antenna tested the performance of the magnetic metamaterial as a substrate. The magnetic metamaterial exhibited enhanced /spl mu/ and /spl epsiv/ as predicted with acceptable loss-factor levels. Models for predicting /spl mu/ and /spl epsiv/ are presented and simulations indicate that permeability can be extended well beyond several GHz with current technology. Permeability in the /spl mu//sub r/=1-4 range is achievable for moderately low-loss applications. The representative antenna miniaturization factor=4-6.4 with efficiency=21-35%.

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Embedded-circuit magnetic metamaterial substrate performance for patch antennas

We propose the novel design of patch antenna over a reactive impedance surface (RIS). The RIS has the minimum interaction with the patch and dramatically enhances antenna performance metrics, namely, size, bandwidth, and efficiency.

Patch antenna over RIS substrate: a novel miniaturized wideband planar antenna design

Metamaterial EM insulators are designed to eliminate mutual coupling between closely packed array elements. This technique allows for array element design in isolation, without consideration of mutual coupling effects. Eliminating mutual coupling also allows for denser packing and higher directivity in antenna arrays. By placing isolation walls along the radiating edges of a patch on a /spl lambda//sub 0//3/spl times//spl lambda//sub 0//3 ground plane a 19.2dB front-to-back ratio is achieved. Metamaterial isolation walls 0.05/spl lambda//sub 0/ thick exhibit -10 dB isolation bandwidths of 2-6% with very low losses for various geometries and greater than 20 dB peak isolation is achieved for array element spacing of 0.2/spl lambda//sub 0/.

K. Buell

Papers

A substrate for small patch antennas providing tunable miniaturization factors

Metamaterial Insulator Enabled Superdirective Array

Embedded-circuit magnetic metamaterial substrate performance for patch antennas

Patch antenna over RIS substrate: a novel miniaturized wideband planar antenna design

Electromagnetic metamaterial insulator to eliminate substrate surface waves