Affiliated with the
Communication & Space
Sciences Laboratory

Novel Electromagnetic Metamaterials

Electromagnetic Bandgap Metamaterials

 

Photograph of a dual-band design for an Electromagnetic Bandgap (EBG) Artificial Magnetic Conducting (AMC) ground plane optimized using a Genetic Algorithm (GA).

Current distribution on an optimized broadband open-sleeve microstrip dipole antenna.

Photograph of a GA optimized broadband low-profile open-sleeve microstrip dipole antenna placed in close proximity to a GA optimized broadband EBG AMC ground plane.

..: Movies :..

1-) Movie showing the interaction of an incident electromagnetic plane wave with a two layer dual-band EBG AMC surface made using a periodic FDTD code developed by members of CEARL: Download AVI

..: References :..

1-) Advances in the Design Synthesis of Electromagnetic Bandgap Metamaterials
by Douglas H. Werner, Douglas J. Kern, Pingjuan L. Werner, Michael J. Wilhelm, Agostino Monorchio, and Luigi Lanuzza
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2-) Multi-band High Impedance Frequency Selective Surfaces
by D. J. Kern, D. H. Werner, R. Mittra, M. J. Wilhelm, and K. H. Church
2002 IEEE International Symposium on Antennas and Propagation and USNC/URSI Radio Science Meeting. San Antonio, Texas, June 16-21.
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3-) A Genetic Algorithm Approach to the Design of Ultra-thin Electromagnetic Bandgap Absorbers
by D. J. Kern and D. H. Werner, July 2003 MOTL

ABSTRACT: A design methodology is presented for utilizing electromagnetic bandgap metamaterials, also known as artificial magnetic conductors, to realize ultra-thin absorbers. One approach that has recently been proposed is to place a resistive sheet in close proximity to a frequency-selective surface acting as an artificial magnetic conductor. However, we demonstrate in this paper that incorporating the loss directly into the frequency selective-surface can eliminate the additional resistive sheet, thereby further reducing the overall thickness of the absorber. The geometrical structure and corresponding resistance of this lossy frequency-selective surface is optimized by using a genetic algorithm to achieve the thinnest possible absorber. Two examples of genetically engineered electromagnetic bandgap metamaterial absorbers are presented and discussed. Go



4-) Genetically Engineered Multiband High-Impedance Frequency Selective Surfaces
by Douglas J. Kern, Douglas H. Werner, Michael J. Wilhelm, and Kenneth H. Church, September 2003 MOTL

ABSTRACT: A methodology is presented for the design synthesis of metamaterials that act as thin multifrequency artificial magnetic conductors. These structures are realized by placing a frequency-selective surface above a conventional prefect electric conductor, separated by a thin dielectric layer. The frequency-selective surface design is optimized using a microgenetic algorithm to operate at multiple, narrow frequency bands. Two examples of genetically engineered multiband high-impedance frequency-selective surfaces (that is, artificial magnetic conductors) are presented and discussed.
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5-) Ultra-thin Electromagnetic Bandgap Absorbers Synthesized via Genetic Algorithms
by D. J. Kern and D. H. Werner
2003 IEEE International Symposium on Antennas and Propagation. Columbus, Ohio, June 22-27.

ABSTRACT: A design methodology is presented for utilizing electromagnetic bandgap meta-materials, also known as artificial magnetic conductors, to realize ultra-thin absorbers. One approach that has recently been proposed is to place a resistive sheet in close proximity to a frequency selective surface acting as an artificial magnetic conductor. However, we demonstrate that incorporating the loss directly into the frequency selective surface can eliminate the additional resistive sheet, thereby further reducing the overall thickness of the absorber. A genetic algorithm is used to optimize the geometrical structure and corresponding resistance of the lossy frequency selective surface in order to achieve the thinnest possible design. Two examples of genetically engineered electromagnetic bandgap meta-material absorbers will be presented and discussed.




6-) Active Negative Impedance Loaded EBG Structures for the Realization of Ultra-Wideband Artificial Magnetic Conductors
D. J. Kern, D. H. Werner and M. J. Wilhelm
2003 IEEE International Symposium on Antennas and Propagation. Columbus, Ohio, June 22-27.

ABSTRACT: A new design methodology is introduced for an ultra-wideband Artificial Magnetic Conductor (AMC) that is based on loading the elements of Electromagnetic Bandgap (EBG) structures with active devices. The types of active loads used for this application belong to the class of devices known as Negative Impedance Converters (NICs). NICs are active two-port networks for which the impedance looking into one port is the negation of the impedance connected to the other port scaled by the impedance conversion coefficient of the device. Several design examples will be presented that demonstrate the considerable enhancement in bandwidth that can be achieved, compared to conventional passive AMC surfaces, by using EBG structures actively loaded with NICs.




7-) A Robust GA-FSS Technique for the Synthesis of Optimal Multiband AMCs with Angular Stability
by L. Lanuzza, A. Monorchio, D. J. Kern and D. H. Werner
2003 IEEE International Symposium on Antennas and Propagation. Columbus, Ohio, June 22-27.

ABSTRACT: A Genetic Algorithm (GA) design methodology is presented for synthesizing multiband Artificial Magnetic Conductors (AMCs) with angular stability. The GA is used to optimize the Frequency Selective Surface (FSS) screen geometry and other design parameters for both multiband operation and stability with respect to the angle of illumination at each operating frequency. The design example presented demonstrates the multiband angular stability for a dual-band AMC at a GPS frequency of 1.575 GHz and a cell phone frequency of 1.96 GHz.




8-) The Design Optimization of Miniature Low Profile Antennas Placed in Close Proximity to High-Impedance Surfaces
by D. H. Werner and P. L. Werner
2003 IEEE International Symposium on Antennas and Propagation. Columbus, Ohio, June 22-27.

ABSTRACT: The objective of this paper is to illustrate a new design optimization procedure for miniaturized antennas placed in the presence of a high-impedance surface (i.e., a Perfect Magnetic Conductor or PMC). It will be demonstrated that antennas can be optimized via a Genetic Algorithm (GA) [1,2] to achieve superior performance characteristics (e.g., input impedance, VSWR, and gain) when placed in close proximity to a PMC ground plane as opposed to a standard Perfect Electric Conducting (PEC) ground plane. For instance, it will be shown that the driving point impedance and, hence, the VSWR of an antenna can be significantly affected by placing it in the presence of a PMC ground plane. A methodology that allows for the compensation of these coupling effects is introduced that is based on optimizing the shape of a miniaturized fractal or stochastic antenna when placed next to a PMC surface. It will also be demonstrated at these genetically optimized antennas exhibit superior performance when compared to conventional half-wave dipoles with the same design specifications. Several case studies are presented here that compare the performance of a specific antenna when operating in the vicinity of a PMC ground plane versus a PEC ground plane. The results of these studies show that in the case of a PMC ground plane, the desired VSWR specifications can be achieved through optimizing the geometries of fractal or stochastic antennas. This technique can be used to successfully design miniature low-profile antennas. We also illustrate the fact that it is not possible to achieve similar results using a conventional PEC ground plane.




9-) Optimization of Multi-band AMC Surfaces with Magnetic Loading
by D. J. Kern, D. H. Werner, and P. L. Werner
2004 IEEE International Symposium on Antennas and Propagation, Monterey, California, June 20-26.

ABSTRACT: This paper presents single-band and multi-band Artificial Magnetic Conducting (AMC) surface designs that are shown to have significant bandwidth enhancement achieved by loading the substrate with a magnetic material. In both cases, a conventional AMC structure consisting of a High Impedance Frequency Selective Surface (HZ-FSS) is optimized using a Genetic Algorithm (GA) for maximum bandwidth. The single-band design operates at 2 GHz, while the multiband design has targeted resonant frequencies of 860 MHz, 1.575 GHz, and 1.88 GHz. These design examples serve to demonstrate that the inclusion of a modest amount of magnetic material within the substrate allows for improved bandwidth at all resonant frequencies.




10-) A Novel Design Approach for an Independently Tunable Dual-Band EBG AMC Surface
by M. G. Bray and D. H. Werner
2004 IEEE International Symposium on Antennas and Propagation, Monterey, California, June 20-26.

ABSTRACT: This paper will investigate a new and novel design approach for creating an independently tunable dual-band Electromagnetic Bandgap (EBG) surface for a use as an Artificial Magnetic Conductor (AMC). The EBG geometry consists of two reactively loaded concentric square loops. The outer loop is used to tune for the first resonance, while the inner loop is used to tune the second resonance. The resonance frequency of each loop is independent of the other and can be tuned down in frequency with capacitors and up in frequency with inductors.




11-) A Broadband Open-Sleeve Dipole Antenna Mounted Above a Tunable EBG AMC Ground Plane
by M. G. Bray and D. H. Werner
2004 IEEE International Symposium on Antennas and Propagation, Monterey, California, June 20-26.

ABSTRACT: A broadband open-sleeve dipole antenna is mounted above a tunable Electromagnetic Bandgap (EBG) surface resulting in a low-profile narrowband antenna system that is tunable over an octave bandwidth. The EBG surface is composed of an array of square metallic patches connected via tunable capacitors over a thin PEC backed dielectric substrate. The capacitors tune the resonance of the surface down in frequency resulting in a low-profile antenna system that can be tuned from 1.2 GHz to 2.3 GHz with a relative thickness of only λ/30 to λ/15 at the lower and upper frequency limits respectively.




12-) A Novel Design Technique for Ultra-thin Tunable EBG AMC Surfaces
by D. J. Kern, M. J. Wilhelm, D. H. Werner, and P. L. Werner
2004 IEEE International Symposium on Antennas and Propagation, Monterey, California, June 20-26.

ABSTRACT: A design methodology is presented for achieving considerable operating bandwidth at low frequencies, specifically below 1 GHz, by the use of an ultra-thin tunable Electromagnetic Bandgap (EBG) Artificial Magnetic Conducting (AMC) surface. By incorporating a high dielectric, ultra-thin substrate into the design of an EBG AMC surface, it is not possible to achieve a large instantaneous bandwidth of operation. However, by utilizing a tunable surface, the narrow bandwidth resulting from the ultrathin high-k design can be exploited and used advantageously. The narrow bandwidth of the structure gives rise to a “channel” frequency determined by the sharp resonance of the AMC surface. By actively tuning the dielectric substrate and hence the overall capacitance of the surface, this resonant frequency can be shifted between channels to cover a reasonably wide bandwidth. Thus, the same bandwidth can be utilized as that of a much thicker structure by tuning the thinner AMC accordingly. This design approach is especially useful at low frequencies below 1 GHz, where the overall thickness of conventional AMC surfaces becomes an issue of practical limitation. Several design examples will be presented for ultra-thin tunable EBG AMC surfaces that have an overall thickness on the order of λ/2000.




13-) The Design Synthesis of Multiband Artificial Magnetic Conductors Using High Impedance Frequency Selective Surfaces
by Douglas J. Kern, Douglas H. Werner, Agostino Monorchio, Luigi Lanuzza, and Michael J. Wilhelm
IEEE Transactions on Antennas and Propagation, Special Issue on Artificial Magnetic Conductors, Soft/Hard Surfaces, and other Complex Surfaces, Vol. 53, No. 1, pp. 8-17, January 2005.

ABSTRACT: This paper introduces several different design methodologies for multiband artificial magnetic conducting (AMC) surfaces. The paper begins by investigating the multiband properties exhibited by a conventional electromagnetic bandgap (EBG) AMC that consists of a frequency selective surface (FSS) on top of a thin dielectric substrate with a PEC back plane. The higher-order resonances associated with these surfaces have not been discussed in detail to date, as previous research has been concerned only with exploiting the primary resonant frequency. However, it will be shown that by understanding and making appropriate use of these higher order resonances, it is possible to design multiband AMC surfaces that work for nearly any desired combination of operating frequencies. The first multiband AMC design approach that will be considered is based on the introduction of FSS screens that have fractal or nearly fractal unit cell geometries. This is followed by a more general and robust genetic algorithm (GA) technique for the synthesis of optimal multiband AMC surfaces. In this case, a GA is used to evolve multiband AMC surface designs by simultaneously optimizing the geometry and size of the FSS unit cell as well as the thickness and dielectric constant of the substrate material. Finally, several examples of multiband AMC surfaces are presented, including some practical dual-band and tri-band designs genetically evolved for operation at GPS and cellular frequencies, as well as an example illustrating the success in creating a multiband AMC surface with angular stability.




14-) Advances in EBG Design Concepts Based On Planar FSS Structures
by D. H. Werner, D. J. Kern, and M. G. Bray
Proceedings of the Loughborough Antennas and Propagation Conference 2005 (invited talk), pp. 259-262, Loughborough University, Loughborough, Leicestershire, UK, April 4-5, 2005.

ABSTRACT: This paper presents an overview of the various applications of planar Frequency Selective Surfaces (FSS) to the synthesis of Electromagnetic Bandgap (EBG) structures that act as metamaterials, such as Artificial Magnetic Conductors (AMCs). Over the past few years, many designs such as single- and dual-band AMC surfaces, tunable AMC surfaces, angularly stable AMC surfaces, ultra-thin EBG absorbers, and EBG metaferrite materials, to name a few, have been investigated and developed successfully at the Pennsylvania State University (PSU) Computational Electromagnetics and Antennas Research Lab (CEARL). Additionally, the most current research presented here examines the ability to utilize an EBG AMC surface to realize a low-profile conformal antenna system that is tunable over an octave bandwidth from 1.2 to 2.3 GHz. An overview of both the previous work and the current EBG with antenna designs will be presented here.

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15-) Reconfigurable Ultra-thin EBG Absorbers Using Conducting Polymers
by T. Liang, L. Li, J. A. Bossard, D. H. Werner, and T. S. Mayer

ABSTRACT: A typical approach to reducing the Radar Cross Section (RCS) of a structure is to coat its surface with some type of lossy material to increase the absorption of electromagnetic waves at the operating frequency of the radar [1, 2]. One of the most popular classical electromagnetic absorber designs is based on the use of so-called Salisbury screens [3]. This structure consists of a resistive metallic screen placed a quarter wavelength above a ground plane, separated by a dielectric layer. More recently, a concept for an ultra-thin absorber that is based on an electromagnetic bandgap (EBG) metamaterial was proposed in [4]. This EBG absorber consists of a lossy Frequency Selective Surface (FSS) screen placed above a conventional metallic ground plane, separated by a relatively thin dielectric layer as depicted in Figure 1. When designed properly, the FSS-based EBG structure acts as a lossy Artificial Magnetic Conductor (AMC) at the desired operating frequency, which makes it possible to achieve ultra-thin absorbers. Typical thicknesses of such designs could range from a tenth of a wavelength to as thin as a fiftieth of a wavelength in some cases. In most EBG absorber designs considered to date, the geometry and material parameters have been engineered to produce a static frequency response. However, for some novel applications, it is also desirable to have the possibility of reconfiguring an absorber so that its frequency response can be shifted or altered altogether while in operation. One way to accomplish this is to use materials, whose electromagnetic properties are adjustable, to fabricate the FSS screen. Among such materials, conducting polymers, which exhibit different degrees of conductivity under certain stimuli when properly doped [5], are good candidates for the lossy FSS screen in an EBG absorber. In the sections that follow, we will describe in detail the design methodology that builds upon the use of conducting polymers to achieve reconfigurable frequency responses in ultra-thin EBG absorbers.




16-) The Design Optimization of Antennas in the Presence of EBG AMC Ground Planes
by D. J. Kern, T. G. Spence, and D. H. Werner

ABSTRACT: A design methodology is presented for the optimization of conformal antennas with Electromagnetic Bandgap (EBG) surfaces to improve antenna performance. The EBG surface is obtained by utilizing a Frequency Selective Surface (FSS) on top of a thin dielectric substrate backed by a metallic ground plane, to act as an Artificial Magnetic Conductor (AMC). The antenna is then placed above the EBG surface to create the integrated EBG conformal antenna. This research demonstrates the ability to optimize both the antenna and EBG surface simultaneously in order to achieve improved antenna performance compared to the antenna and the EBG surface optimized separately. Results are presented for a broadband EBG conformal antenna system that operates from 5.5 to 7.1 GHz with a center frequency of 6.3 GHz.




17-) Magnetic Loading of EBG AMC Ground Planes and Ultrathin Absorbers for Improved Bandwidth and Reduced Size
by D. J. Kern, and D. H. Werner
Microwave and Optical Technology Letters, Vol. 48, No. 12, pp. 2468 - 2471, December 2006.

ABSTRACT: This paper demonstrates the advantages of magnetic loading within the substrate of an electromagnetic bandgap (EBG) surface. A conventional EBG surface has been shown to act as an artificial magnetic conductor over a narrow bandwidth. This paper demonstrates that by magnetic loading of the substrate, increased operating bandwidth is achieved for each resonant frequency. In addition, previous research has revealed that an ultrathin electromagnetic absorber design can be obtained by introducing loss into the frequency selective surface of an EBG absorber. It is now shown that a further reduction in thickness is possible by including a small amount of magnetic permeability within the dielectric substrate material.
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18-) Wideband Dipoles on Electromagnetic Bandgap Ground Planes
by Lida Akhoondzadeh-Asl, Douglas J. Kern, Peter S. Hall, and Douglas H. Werner

ABSTRACT: The performance of broadband dipole antennas above electromagnetic bandgap (EBG) structures is investigated. Two different structures are examined. One is a diamond dipole over an EBG with square patch elements optimized by hand and the other an open sleeve dipole over an EBG optimized by a genetic algorithm (GA). Both configurations demonstrate that a low profile dipole antenna over an EBG can have a broad bandwidth. Careful design of both is required and in particular for best results, the antenna-EBG system should be optimized together, rather than as separate components. The performance is compared to an absorber backed wideband dipole antenna and it is found that the gain is significantly increased, whilst the bandwidth is reduced. In general, for the diamond dipole antenna return loss bandwidths of over 2:1 (67%) have been achieved, although radiation pattern control is difficult and reduces the bandwidth to the order of 1.4:1 (33%). The sleeve dipole over an EBG achieved a bandwidth of 1.28:1 (26%). The realized gain, which is power gain reduced by input match loss, of both structures are approximately the same. GA optimization and parametric studies seem to suggest that bandwidths significantly greater than these are difficult to achieve.




19-) A Versatile Design Strategy for Thin Composite Planar Double-Sided High-Impedance Surfaces
by Zikri Bayraktar, Micah D. Gregory, Xiande Wang, and Douglas H. Werner

ABSTRACT: A novel methodology is introduced for the design syn- thesis of thin planar realizations of volumetric high-impedance or artificial magnetic conducting surfaces (AMC). The design syn- thesis involves optimization of two different metallic frequency se- lective surface (FSS) type structures printed on each side of a thin dielectric substrate material. This technique eliminates the need for a complete metallic backplane common in conventional AMC designs, making use of the same dielectric substrate for two high- impedance surfaces; one on each side. Optimization of the FSS unit cell geometries is carried out with a robust genetic algorithm (GA) technique that is combined with a full-wave periodic finite el- ement boundary integral (PFEBI) electromagnetic simulation code for fast and accurate optimization of desired AMC performance at a single frequency or over multiple frequency bands. Several ex- amples of thin AMC ground planes are optimized for use in the X-band. Additional design examples that provide AMC behavior on one side and absorber behavior on the other are also provided. Lastly, an example illustrating the utility of the double-sided AMC separator structure is shown for a design targeting the standard Wi-Fi frequencies of 2.4 GHz and 5.2 GHz.




20-) A Frequency-Tunable Metamaterial-Based Antenna Using a Reconfigurable AMC Groundplane
by Marco Salucci, Giacomo Oliveri, Micah Gregory, Douglas Werner, Andrea Massa
Proceedings of The 8th European Conference on Antennas and Propagation (EuCAP), The Hague, The Netherlands, 6-11 April 2014.

ABSTRACT: The design of a low-profile narrowband antenna that is tunable over a wide frequency range is presented. A spline-based Ultra-Wideband (UWB) antenna is synthesized by means of a time-domain-based PSO and is mounted on top of a reconfigurable Artificial Magnetic Conductor (AMC) obtained by replicating a square unit cell in a 15x15 periodic lattice. The AMC is composed by a planar array of periodic metallic strips printed on top of a PEC-backed dielectric substrate, connected by tunable capacitors (varactors), and has been designed to work within the 1-4 [GHz] bandwidth. The reflection coefficient of the resulting narrowband antenna system can be easily controlled inside a wide frequency range by tuning the capacitance value C of the varactors inside the AMC groundplane.

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