CiteULike: dcastro's metamaterial

Enabling RF/microwave devices using negative-refractive-index transmission-line (NRI-TL) metamaterials

GV Eleftheriades — 2008-07-24T15:53:31-00:00

Antennas and Propagation Magazine, IEEE, Vol. 49, No. 2. (2007), pp. 34-51.

Metamaterials are artificially engineered structures with unusual electromagnetic properties. In this article, we review the implementation of isotropic metamaterials that exhibit a negative permittivity and a negative permeability, thus leading to a negative index of refraction. Specifically, the article focuses on transmission-line metamaterials, which are planar structures comprising a network of distributed transmission lines loaded periodically with inductors, L, and capacitors, C, in a "high-pass" configuration. The periodic unit cell is much smaller than the wavelength, thus leading to an effective medium in which the lumped loading elements can be either discrete (chip) or printed. Based on such negative-refractive-index transmission-line (NRI-TL) metamaterials, several RF/microwave devices are presented, including microwave lenses that can overcome the diffraction limit, compact phase-shifting lines and associated broadband series-fed power dividers, electrically small antennas, antenna feed networks and baluns, backward leaky-wave antennas, and high-directivity coupled-line couplers and reflectometers.

Negative Refraction at Visible Frequencies

Henri Lezec — 2007-05-29T21:35:32-00:00

Science, Vol. 316, No. 5823. (20 April 2007), pp. 430-432.

Nanofabricated photonic materials offer opportunities for crafting the propagation and dispersion of light in matter. We demonstrate an experimental realization of a two-dimensional negative-index material in the blue-green region of the visible spectrum, substantiated by direct geometric visualization of negative refraction. Negative indices were achieved with the use of an ultrathin Au-Si3N4-Ag waveguide sustaining a surface plasmon polariton mode with antiparallel group and phase velocities. All-angle negative refraction was observed at the interface between this bimetal waveguide and a conventional Ag-Si3N4-Ag slot waveguide. The results may enable the development of practical negative-index optical designs in the visible regime. 10.1126/science.1139266

Experimental verification of backward-wave radiation from a negative refractive index metamaterial

Anthony Grbic — 2008-07-24T15:44:19-00:00

Journal of Applied Physics, Vol. 92, No. 10. (2002), pp. 5930-5935.

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A novel metamaterial-inspired electrically small antenna fed by CPW

Meng Li — 2008-07-24T12:21:02-00:00

Microwave and Millimeter Wave Technology, 2008. ICMMT 2008. International Conference on, Vol. 4 (2008), pp. 1613-1616.

This article presents the design of an inexpensive, efficient, and electrically small antenna based on metamaterial- inspired structure fed by the coplanar waveguide (CPW). The size of the proposed antenna is 12 mm x 12 mm with the resonant frequency of 1.47 GHz. Details of the proposed antenna are presented, with full-wave simulation results to support the design.

On the Radiation Characteristics of Right- and Left-Handed Microstrip Patch Antenna Designs

JA Fladie — 2008-07-24T12:21:04-00:00

Antennas and Wireless Propagation Letters, IEEE, Vol. 5, No. 1. (2006), pp. 563-565.

Theoretical left-handed materials have been shown to reduce the size of a resonant microstrip antenna while maintaining or increasing impedance bandwidth. This work discusses the implications of the left-handed materials on the radiation characteristics of such structures. The source fields and radiation characteristics of left- and right-handed microstrip patch antenna designs are studied theoretically and investigated further using equivalence theory and an approximate radiating slot model. The work indicates that the antenna miniaturization enabled by the use of left-handed materials results in an electrically small antenna with an omnidirectional rather than a broadside radiation pattern when operated in the first resonant mode

Investigations on Volumetric Layered Transmission Line Metamaterials for Antenna Applications

F Bongard — 2008-07-24T12:21:07-00:00

Antennas and Propagation, 2007. EuCAP 2007. The Second European Conference on (2007), pp. 1-7.

This paper presents the investigations on a volumetric negative refractive index metamaterial (MTM) based on the transmission line (TL) approach to be used as a substrate for patch antennas. A prototype of such a structure, obtained by stacking several 1D planar TL based MTM, has been designed and built. Possibilities of using this kind of MTM substrate for the implementation of multi-frequency patch antennas are discussed.

On Impedance Bandwidth of Resonant Patch Antennas Implemented Using Structures with Engineered Dispersion

Pekka Ikonen — 2008-07-24T12:21:13-00:00

(10 Nov 2006)

We consider resonant patch antennas, implemented using loaded transmission-line networks and other exotic structures having engineered dispersion. An analytical expression is derived for the ratio of radiation quality factors of such antennas and conventional patch antennas loaded with (reference) dielectrics. In the ideal case this ratio depends only on the propagation constant and wave impedance of the structure under test, and it can be conveniently used to study what kind of dispersion leads to improved impedance bandwidth. We illustrate the effect of dispersion by implementing a resonant patch antenna using a periodic network of LC elements. The analytical results predicting enhanced impedance bandwidth compared to the reference results are validated using a commercial circuit simulator. Discussion is conducted on the practical limitations for the use of the proposed expression.

Modeling of patch antennas partially loaded with dispersive backward-wave materials

SA Tretyakov — 2008-07-24T12:17:33-00:00

Antennas and Wireless Propagation Letters, IEEE, Vol. 4 (2005), pp. 266-269.

In this letter, a transmission-line model for a patch antenna where a half of the patch is loaded with a dispersive material with negative parameters is used to explore the antenna bandwidth characteristics. Possibilities to reduce the antenna size using the phase compensation in the loaded patch are considered. Resonant properties of patch antennas loaded with a dispersive material and with a nondispersive medium having /spl epsi/=-/spl epsi//sub 0/,/spl mu/=-/spl mu//sub 0/ are compared with the unloaded case.

Patch antennas partially loaded with a dispersive backward-wave material

ME Ermutlu — 2008-07-24T11:59:05-00:00

Antennas and Propagation Society International Symposium, 2005 IEEE, Vol. 2A (2005), pp. 6-9.

In this work a transmission-line model for a patch antenna where a half of the patch is loaded with a dispersive material with negative parameters is used to explore the antenna bandwidth characteristics. Possibilities to reduce the antenna size using the phase compensation in the loaded patch are considered. Resonant properties of patch antennas loaded with a dispersive material and with a non-dispersive medium having ε<inf>0</inf>=-ε<inf>o</inf>, μ<inf>0</inf>=-μ<inf>0</inf>are compared with the unloaded case.

A new miniaturized annular ring patch resonator partially loaded by a metamaterial ring with negative permeability and permittivity

SF Mahmoud — 2008-07-24T11:59:01-00:00

Antennas and Wireless Propagation Letters, IEEE, Vol. 3 (2004), pp. 19-22.

A new annular ring microstrip patch resonator with reduced size is proposed. The underlying material is partially occupied by a ring of metamaterial with negative permittivity and permeability. It is shown that the resonant frequency of the TM/sub 110/ cavity mode can be made as small as we desire by proper choice of dimensions and material parameters. Relevance to the design of compact patch antennas for wireless receivers is indicated.

A positive future for double-negative metamaterials

Nader Engheta — 2008-05-15T23:15:35-00:00

Microwave Theory and Techniques, IEEE Transactions on, Vol. 53, No. 4. (2005), pp. 1535-1556.

Metamaterials (MTMs), which are formed by embedding inclusions and material components in host media to achieve composite media that may be engineered to have qualitatively new physically realizable response functions that do not occur or may not be easily available in nature, have raised a great deal of interest in recent years. In this paper, we highlight a large variety of the physical effects associated with double- and single-negative MTMs and some of their very interesting potential applications. The potential ability to engineer materials with desired electric and magnetic properties to achieve unusual physical effects offers a great deal of excitement and promise to the scientific and engineering community. While some of the applications we will discuss have already come to fruition, there are many more yet to be explored.

Compact Fully Integrated GaAs Left-Handed Bandpass Filter for Ultrawide Band Wireless Applications

W Tong — 2008-07-17T19:56:34-00:00

Antennas and Propagation, 2007. EuCAP 2007. The Second European Conference on (2007), pp. 1-6.

A GaAs MMIC technology of the novel compact left-handed bandpass filter consisting of one left-handed (LH) transmission line (TL) and one dual composite right/lefthanded (D-CRLH) TL is presented. The D-CRLH is the dual of the conventional CRLH in the sense that it consists of a LC parallel-tank impedance and of a LC series-tank admittance. In contrast to the conventional CRLH TL which has LH operation at low-frequency and RH one at high-frequency, the D-LH TL exhibits its LH band at high frequencies and its RH band at low frequencies. Thus, utilizing the high pass property of LH and low pass property of D-CRLH, a bandpass filter can be constructed. In this paper, this novel idea is realized by MMIC technology. The proposed filter exhibits a broad passband from 6.2 GHz to 20.8 GHz with a size of 1.43 mm<sup>2</sup>.

A Diplexer Based on the Spatial Filtering Property of Planar Anisotropic Transmission-Line Metamaterials

JKH Wong — 2008-07-17T19:56:22-00:00

Antenna Technology Small Antennas and Novel Metamaterials, 2006 IEEE International Workshop on (2006), pp. 241-244.

Analysis and Application of Metamaterial Spiral-Based Transmission Lines

T Kokkinos — 2008-07-17T19:56:21-00:00

Antenna Technology: Small and Smart Antennas Metamaterials and Applications, 2007. IWAT '07. International Workshop on (2007), pp. 233-236.

Double spiral resonators, properly backed on grounded substrates and specifically arranged in periodic arrays, support backward waves at their fundamental resonance. Transmission lines that are composed of these spirals and their potential use in microwave applications are studied in this paper. Subsequently to a periodic, full-wave analysis of the double spiral resonators, the fabrication and measurement of the spiral-based transmission lines experimentally validate that they support backward waves over a fractional bandwidth of approximately 13%. For the in depth analysis of these lines, an equivalent circuit, that can describe all the phenomena associated with the operation of the double spirals as structural unit cells of metamaterials, is extracted. Finally, an ultra compact diplexer that originates its operation on spiral-based transmission lines is presented, exhibiting just one of the possible ways that metamaterial lines can be employed in microwave applications

Self-diplexed antenna based on metamaterials for RFID application

E Ugarte-Mufioz — 2008-07-17T19:56:17-00:00

Applied Electromagnetics and Communications, 2007. ICECom 2007. 19th International Conference on (2007), pp. 1-4.

In this paper a self-diplexed antenna is proposed for a RFID transponder application. The development cycle is divided into two stages: antenna design and filters design. The antenna is based on a square microstrip patch filled with metamaterial structures. The inclusion of these structures allows simultaneous operation over several frequencies, which can be arbitrarily chosen. The antenna working frequencies are chosen to be 2.45 GHz (receiver) and 1.45 GHz (transmitter). In addition, the antenna is fed through two orthogonal coupled microstrip lines, which provides high isolation between both ports (> 20 dB). Some filters based on left-handed particles are coupled to the antenna feeding microstrip lines have been included to avoid undesired interferences. This approach avoids using of an external filter or diplexer, providing high size reduction and a compact self-diplexed antenna.

Electromagnetic Metamaterials: Physics and Engineering Explorations (Engheta, N. and Ziolkowski, R.W.; 2006) [Book Review]

V Fusco — 2008-06-30T09:11:18-00:00

Antennas and Propagation Magazine, IEEE, Vol. 49, No. 4. (2007), pp. 137-139.

This book is excelland and consists of 27 contributing authors. It maximizes written descriptions based on standard basic electronic-engineering principles and uses mathematics in a concise format in order to impress the core basis upon which each major concept presented is predicated. As with most multi-authored texts on a single topic, the book contains some material that is repeated across several chap¬ters. However, the repetition is minimal, and at times aids the reader by giving different perspectives on the same topic. This book is produced to a very high standard, with numerous color illustrations that allow the reader to rapidly assimilate the informa¬tion that they are designed to convey.

Left-handed propagation media via photonic crystal and metamaterials

Thibaut Decoopman — 2008-06-29T18:30:15-00:00

Comptes Rendus Physique, Vol. 6, No. 6. ( 2005), pp. 683-692.

We review the electromagnetic properties of artificial structures such as photonic band gap materials (Electromagnetic Band Gap at microwaves) and metamaterials with main emphasis on backward (left-handed) propagation media. We consider free space and guiding structures by showing how the interaction of the electromagnetic wave with periodic dielectric (PBGs) and double negative metallic structures (DNGs) yields a negative refractive index. Some of the potential applications in connection with negative index media are briefly discussed such as focusing for a flat lens and phase advance for a left handed transmission line. To cite this article: T. Decoopman et al., C. R. Physique 6 (2005).

Slow Wave Structures for Miniature Antennas

John Volakis — 2008-06-29T18:29:53-00:00

Anti-counterfeiting, Security, Identification, 2007 IEEE International Workshop on (2007), pp. 5-8.

Engineered materials, such as new composites, electromagnetic bandgap, and periodic structures have attracted considerable interest in recent years due to their remarkable and unique electromagnetic properties. Among this class of media are the magnetic photonic (MPC) and degenerate band edge (DBE) crystals. These periodic media have the concurrent characteristics of wave slow down and impedance matching at their dielectric interface. The first allows for miniaturization, and the latter is equivalent to radiation efficiency. Overall these properties are a consequence of the anisotropic nature of the periodic media, allowing for internal phase shifting that leads to ray collimation for best aperture utilization. To a degree, they emulate zero index materials, and thus (planar) layers of the material serve the same purpose as a reflector dish. This important property of the MPC and DBE structures will be discussed at the meeting. The main focus of this work is two-fold: 1. The realization (in terms of material availability and fabrication) of the proposed periodic media, and their theoretical and measured performance for antenna applications. Specifically, we will pursue feed arrangements, impedance matching and metallizations/printings for maximum aperture efficiency. 2. Introduction of a concept that allows for emulation of the anisotropic properties of MPC/DBE media using a novel coupled line printed approach. This concept allows for the realization of the wave slow-down and impedance matching within a printed microwave structure, leading to new design methodologies for microwave components, including couplers, filters and printed antenna devices.

Backward-wave meta-materials-a brief review

S Hrabar — 2008-06-29T18:29:15-00:00

Applied Electromagnetics and Communications, 2003. ICECom 2003. 17th International Conference on (2003), pp. 245-250.

One of the currently most active areas in electromagnetics deals with artificial materials that support propagation of backward-waves ('left-handed', 'backward-wave' or 'double negative' materials). This paper reviews some representative research results published in period since introduction of 'backward-wave' materials (May 2000) until now (May 2003). It appears that majority of published reports are still concerned with very fundamental issues which involve mathematical formulation, experimental verification and understanding of new, not previously observed physical phenomena. So far, there have been very few successfully realised engineering applications of backward-wave materials, mainly in technology of planar microwave circuits. The other applications, which would involve more striking phenomena such as negative refraction, 'amplification' of evanescent waves and 'super-resolution' focusing, although already proposed, are yet to be seen.

From electromagnetic bandgap to left-handed metamaterials: Modelling and applications

Yang Hao — 2008-06-29T18:26:30-00:00

Journal of Zhejiang University - Science A, Vol. 7, No. 1. (23 January 2006), pp. 34-40.

Abstract In this paper, numerical modelling of left-handed materials (LHMs) is presented using in-house and commercial software packages. Approaches used include the finite-difference time-domain (FDTD) method, finite element method (FEM) and method of moments (MoMs). Numerical simulation includes verification of negative refraction and “perfect lenses” construction, investigation of evanescent wave behaviour in layered LHMs, reversed Snell’s Law in electromagnetic band gap (EBG)-like structures and construction of LHMs using modified split ring resonators (SRRs). Numerical results were verified to be in good agreement with theory. At the end of this paper, potential applications of LHMs in microwave engineering are discussed.

Broad-bandwidth and low-loss metamaterials: Theory, design and realization

Le-Wei Li — 2008-06-29T18:25:25-00:00

Journal of Zhejiang University - Science A, Vol. 7, No. 1. (23 January 2006), pp. 5-23.

Abstract In this paper, we summarize some recent activities in the field of metamaterial research at the National University of Singapore (NUS). Integral equations are applied for electromagnetic modelling of supernatural materials. Some special characteristics of the metamaterials are shown. Moreover, quasi-static Lorentz theory and numerical method (i.e., the method of moments for solving the electric field integral equation) and the transmission line theory are both presented to obtain the effective constitutive relations of metamaterials, respectively. Finally, feasibility of fabricating metamaterials based on analysis of equivalent transmission line model in the microwave spectrum and even higher is also shown and correspondingly some broad-bandwidth and low-loss metamaterial structures are designed and synthesized.

Modelling metamaterial transmission lines: a review and recent developments

F Aznar — 2008-06-29T18:21:44-00:00

Opto-Electronics Review

Abstract This review paper is devoted to the discussion and comparison of the lumped element equivalent circuit models of the different types of metamaterial transmission lines that have been proposed so far, namely the CL-loaded lines, and those lines based on the resonant type approach. The latter category comprises both artificial lines loaded with split ring resonators (SRRs), or related topologies, and metamaterial transmission lines based on complementary split ring resonators (CSRRs). It will be the main aim of this paper to clearly justify the circuit elements of the models (and link such elements to the line physics and topology), to compare the different lines to the light of these models, and to point out the advantages and drawbacks of the different metamaterial transmission lines. As long as metamaterial transmission lines are exhaustively used for the design of compact microwave and millimeter wave components with improved performance and/or based on new functionalities, and their synthesis is based on the lumped element equivalent circuits, this paper is of actual interest for RF/microwave engineers and in general to those readers involved in metamaterial research and applications.

Full-wave verification of the fundamental properties of left-handed materials in waveguide configurations

C Caloz — 2008-06-29T18:02:13-00:00

Journal of Applied Physics, Vol. 90, No. 11. (2001), pp. 5483-5486.

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Brief Overview of Recent Developments on Negative Phase-Velocity Mediums (alias Left-Handed Materials)

Akhlesh Lakhtakia — 2008-06-29T18:01:26-00:00

AEU - International Journal of Electronics and Communications, Vol. 56, No. 6. (2002), pp. 407-410.

Summary This brief overview covers a rapidly occurring development in the area of microwave composite materials: isotropic dielectric-magnetic mediums wherein the phase velocity vector and the time-averaged Poynting vector are oppositely directed. Such materials have also been inappropriately designated as left-handed materials. Ramifications for aberration-free lenses, homogenization approaches, and complex mediums are also presented.

Nonlinear propagation of electromagnetic waves in negative-refraction-index composite materials

I Kourakis — 2008-06-29T18:01:01-00:00

Physical Review E (Statistical, Nonlinear, and Soft Matter Physics), Vol. 72, No. 1. (2005)

We investigate the nonlinear propagation of electromagnetic waves in left-handed materials. For this purpose, we consider a set of coupled nonlinear Schrödinger (CNLS) equations, which govern the dynamics of coupled electric and magnetic field envelopes. The CNLS equations are used to obtain a nonlinear dispersion, which depicts the modulational stability profile of the coupled plane-wave solutions in left-handed materials. An exact (in)stability criterion for modulational interactions is derived, and analytical expressions for the instability growth rate are obtained.

Negative Refractive Index in Left-Handed Materials

David Smith — 2008-06-29T17:59:24-00:00

Physical Review Letters, Vol. 85, No. 14. (2 October 2000), 2933.

Nonlinear Properties of Left-Handed Metamaterials

Alexander Zharov — 2008-06-29T17:58:14-00:00

Physical Review Letters, Vol. 91, No. 3. (18 July 2003), 037401.

Superluminal transmission of information through an electromagnetic metamaterial

Richard Ziolkowski — 2008-06-29T17:28:03-00:00

Physical Review E, Vol. 63, No. 4. (23 March 2001), 046604.

Causality and double-negative metamaterials

Richard Ziolkowski — 2008-06-29T17:27:24-00:00

Physical Review E, Vol. 68, No. 2. (2003), 026615.

Wave propagation in media having negative permittivity and permeability

Richard Ziolkowski — 2008-06-29T17:22:58-00:00

Physical Review E, Vol. 64, No. 5. (30 October 2001), 056625.

Subwavelength, Compact, Resonant Patch Antennas Loaded With Metamaterials

A Alu — 2008-06-28T00:05:01-00:00

Antennas and Propagation, IEEE Transactions on, Vol. 55, No. 1. (2007), pp. 13-25.

We analyze the matching and radiation properties of subwavelength resonant patch antennas filled with double-negative, double-positive, and/or single-negative metamaterial blocks. Analyzing the theoretical limits inherently present when loading such common radiators with metamaterials, we show how these configurations may exhibit in principle an arbitrarily low resonant frequency for a fixed dimension, but they may not necessarily radiate efficiently when their size is electrically small. However, interesting possibilities are suggested to overcome these limitations by employing circular or more complex patch geometries in order to select specific modes that, when appropriate loading ratios between the filling materials are chosen, also ensure radiation performance comparable qualitatively with a regular patch radiator of standard dimensions. Realistic numerical simulations, considering material dispersion, losses and the presence of the antenna feed are presented, showing how a practical realization is foreseeable. This may open novel venues in the design of small-scaled radiators with enhanced performance, which is of interest for many applications

Enabling rfimicrowave devices using negative refractive-index transmission-line metamaterials

GV Eleftheriades — 2008-06-27T23:48:42-00:00

Metamaterials for Microwave and (Sub) Millimetre Wave Applications: Photonic Bandgap and Double Negative Designs, Components and Experiments, 2003. IEE Seminar on (2003), pp. 12/1-12/8.

Design and experimental demonstration of active RF metamaterials

BI Popa — 2008-06-24T22:32:18-00:00

Antennas and Propagation International Symposium, 2007 IEEE (2007), pp. 2546-2549.

In this paper,an alternative method is proposed expand the usability of metamaterials by employing active elements to cancel losses and/or reduce dispersion. Since they can be designed in a more controllable fashion than their electrical counterparts, this work will focus on developing magnetic active particles capable of generating negative permeability metamaterials. However, the principles discussed in this paper can also be applied to obtain active electric materials.

A critical look at metamaterials for antenna-related applications

R Mittra — 2008-06-24T07:28:27-00:00

Journal of Communications Technology and Electronics, Vol. 52, No. 9. (2007), pp. 972-978.

Abstract The main objective of this paper is to take a critical look at the promise of metamaterials for antenna performance enhancement and to recommend directions of possible future research on these materials.

Metamaterials for optical and radio communications

Boubacar Kante — 2008-04-14T09:59:41-00:00

Comptes Rendus Physique, Vol. 9, No. 1. (January 2008), pp. 31-40.

We present here two examples of metamaterials for applications in the telecoms domain. The first concerns the realization of an ultra compact directive electronically reconfigurable antenna. The second deals with an infrared left-handed metamaterial working under normal incidence. For the first application, we use a composite phase varying metamaterial. An adjustable resonance radiating frequency between 7.9 and 8.2 GHz is obtained and a drastic enhancement in the directivity of the antenna is observed for a cavity thickness as small as [lambda]/75 (0.5 mm!). Concerning the second application we present simulations and measurements of a metamaterial made of gold wires and C-shaped nanostructures on silicon at infrared wavelengths. Both plasmonic resonances occur at 1.7 and 4.2 [mu]m, corresponding to a simultaneously negative permittivity and permeability. A simplified version of this metamaterial is realized in the microwave domain. This new metamaterial is characterized and the left-handed behavior is experimentally demonstrated. To cite this article: B. Kante et al., C. R. Physique 9 (2008).

A Broadband Quadrature Power Splitter Using Metamaterial Transmission Line

Chao-Hsiung Tseng — 2008-06-24T07:20:16-00:00

Microwave and Wireless Components Letters, IEEE, Vol. 18, No. 1. (2008), pp. 25-27.

A broadband quadrature power splitter (QPS) is developed using the metamaterial transmission line (MM TL). It consists of a Wilkinson power divider and two phase-adjusting TLs, namely a MM TL and a microstrip (MS). The slope of the phase-response curve of the MM TL is synthesized to be the same as that of the MS along with the 90deg phase increment at two design frequencies. Hence, the broadband quadrature phase difference over the desired frequency range can be obtained. In this letter, the QPS is developed at the center frequency of 2 GHz. Over the frequency range of 1.1-3.5 GHz, an amplitude imbalance of less than 0.9 dB and a phase error of less than plusmn5deg have been experimentally demonstrated.

Dynamic radiation pattern diversity (DRPD) MIMO using CRLH leaky-wave antennas

JF Frigon — 2008-06-24T07:20:03-00:00

Radio and Wireless Symposium, 2008 IEEE (2008), pp. 635-638.

This paper presents a dynamic radiation pattern diversity (DRPD) MIMO wireless system where the antennas radiation patterns are electronically controlled in real-time. The adopted antenna elements are composite right/left-handed (CRLH) microstrip leaky-wave (LW) antennas for which the beam direction can be electronically scanned in a continuous manner from backfire to endfire and the beam shape can be controlled. This system offers a tremendous amount of flexibility in tuning the channel transfer matrix to increase the system performance. Based on this architecture, we propose two simple radiation pattern control algorithms. The first one requires no feedback and averages out the channel fades while the second one requires a simple feedback at the receiver to select the beam pattern maximizing the performance metric. The capacity of both algorithms is derived and analyzed using Monte Carlo simulations. The results show that these algorithms significantly improve the wireless link outage performance in a slow fading environment and increase the diversity gain of a MIMO system for a fixed multiplexing gain.

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

F Bilotti — 2008-06-24T07:20:05-00:00

Antennas and Propagation, IEEE Transactions on, Vol. 55, No. 8. (2007), pp. 2258-2267.

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 Miniaturized Metamaterial Patch Antennas With <formula formulatype="inline"> <tex>$mu$</tex></formula>-Negative Loading

F Bilotti — 2008-06-24T07:12:24-00:00

Antennas and Propagation, IEEE Transactions on, Vol. 56, No. 6. (2008), pp. 1640-1647.

<para> Recent theoretical studies have shown that circular patch antennas loaded by an inhomogeneous substrate partially filled with a <formula formulatype="inline"> <tex>$mu$</tex></formula>-negative (MNG) metamaterial may in principle support a resonant radiating mode, even if the total size of the radiator is significantly smaller than the wavelength of operation. In those theoretical analyses, MNG metamaterials have been assumed as continuous, isotropic and readily available materials, characterized by a proper dispersion in frequency and by inherent ohmic losses. The fabrication of such compact antennas, however, would require the major effort of designing proper subwavelength inclusions that realize the MNG behavior of the substrate, and consequently a careful design of their geometry, location and orientation. The fabrication of a fully isotropic MNG sample to reside underneath the sub-wavelength patch, moreover, may be challenging with the current technological limitations. In this paper, we first show that the proposed sub-wavelength radiator may operate even when the fabricated MNG sample is not isotropic, due to the specific polarization of the magnetic field in the MNG region. Then, we propose a complete design of the magnetic inclusions, presenting full-wave numerical simulations of the structure, which effectively supports the expected resonant mode, despite the small size of the antenna. The comparisons among analytical results of the patch loaded by: (a) the ideal MNG sample applying a simple cavity model; (b) full-wave numerical simulations of the same antenna considering the presence of the feed; and (c) full-wave numerical simulations of the antenna loaded by the proposed magnetic inclusions, show how our design effectively simulate the presence of an MNG sample, allowing the realistic design of a sub-wavelength metamaterial patch antenna with satisfactory matching and radiating features. This may open up new venues in the realization of efficien- t metamaterial radiating components for practical purposes. </para>

Narrow-beamwidth T-shaped monopole antenna fabricated from metamaterial wires

D Kim — 2008-06-24T07:06:24-00:00

Electronics Letters, Vol. 44, No. 3. (2008), pp. 180-182.

A simple T-shaped monopole is converted into a metamaterial antenna by loading lumped capacitors and inductors on the metal wire. The new metamaterial antenna could sustain a half-wave resonance even when its length exceeds several free-space wavelengths. An 80 mm-long monopole initially resonating at 1.3 GHz is modified to operate at 3.6 GHz with a reduced 3 dB H-plane beamwidth of 48deg.

Textured Surface Assisted Active Antenna Performance

VF Fusco — 2008-06-24T07:05:28-00:00

Antennas and Propagation, 2007. EuCAP 2007. The Second European Conference on (2007), pp. 1-5.

In this paper the possibilities associated with augmenting the properties of millimeter wave active antennas performing reflection amplifier or short range radar action by using the properties of a 2D metamaterial textured surface are discussed. The objective here is to effect simultaneous improvements in antenna gain and reduction of un-modulated backscatter from the environment in which the module is housed. A reflection amplifier module with up to 14 dB gain at 21 GHz is described which is capable of either direct detection or modulated backscatter of amplitude modulated incident signals. A detection sensitivity of up to -75 dBm has been achieved. In addition the module, when suitably biased, can be made to operate as a short range radar with up to - 120dBm sensitivity in a 30Hz bandwidth. An ultra thin meta material based absorber with -16dB reflection loss provides the means for backscatter reduction which is compliant with the planar nature of the module. Further the inclusion of the absorber is shown to increase the gain of the module by 4dB.

At and below the chu limit: passive and active broad bandwidth metamaterial-based electrically small antennas

RW Ziolkowski — 2008-06-24T07:05:27-00:00

Microwaves, Antennas & Propagation, IET, Vol. 1, No. 1. (2007), pp. 116-128.

The solution to the canonical problem of a radiating infinitesimal electric dipole antenna that is centred in a multilayered, concentric metamaterial-based spherical shell system is presented. It is demonstrated that when this system is electrically small, a specifically designed homogenous and isotropic epsilon-negative (ENG) layer can function as a distributed matching element to the antenna enabling a resonant radiation behaviour. A finite element model of the corresponding centre-fed cylindrical dipole antenna-based resonant system confirms that such designed ENG-based spherical layers can act as a distributed matching element, which can be optimised to produce a reactance free, resistively matched and, hence, efficient radiating system. Several limits on the dispersion properties of the homogenous and isotropic ENG media used in these matching layers are considered and their impact on the bandwidth of these resonant systems is established. Although the dispersionless resonant antenna-ENG system has a bandwidth substantially below the Chu limit, the bandwidths of the corresponding dispersive systems are shown to be at or just slightly below the Chu limit. An analytical model of an idealised gaseous plasma-based ENG layer sandwiched between two glass layers, a potential realisation of these metamaterial-based ENG spherical shell systems, is introduced and its solution is used to study these efficiency and bandwidth issues further. Resonant systems based on active ENG metamaterial layers realised with two types of idealised gain medium models are shown to have bandwidths that approach the idealised dispersionless medium values and, consequently, are substantially below the Chu limit

High-gain active composite right/left-handed leaky-wave antenna

FP Casares-Miranda — 2008-06-24T07:03:54-00:00

Antennas and Propagation, IEEE Transactions on, Vol. 54, No. 8. (2006), pp. 2292-2300.

A novel high-gain active composite right/left-handed (CRLH) metamaterial leaky-wave antenna (LWA) is presented. This antenna, which is designed to operate at broadside, is constituted by passive CRLH leaky-wave sections interconnected by amplifiers, which regenerate the power progressively leaked out of the structure in the radiation process in order to increase the effective aperture of the antenna and thereby its gain. The gain is further enhanced by a matching regeneration effect induced by the quasi-unilateral nature of the amplifiers. Both the cases of quasi-uniform and binomial field distributions, corresponding to maximum directivity and minimum side-lobe level, respectively, have been described. An active LWA prototype is demonstrated in transmission mode with a gain enhancement of 8.9 dB compared to its passive counterpart. The proposed antenna can attain an arbitrarily high gain by simple increase of the length of the structure, without penalty in terms of return loss and without requiring a complicated feeding network like conventional array antennas.

A broadband series power divider using zero-degree metamaterial phase-shifting lines

MA Antoniades — 2008-06-16T07:03:20-00:00

Microwave and Wireless Components Letters, IEEE, Vol. 15, No. 11. (2005), pp. 808-810.

A metamaterial 1:4 series power divider that provides equal power split to all four output ports over a large bandwidth is presented, which can be extended to an arbitrary number of output ports. The divider comprises four nonradiating metamaterial lines in series, incurring a zero insertion phase over a large bandwidth, while simultaneously maintaining a compact length of /spl lambda//sub 0//8. Compared to a series power divider employing conventional one-wavelength long meandered transmission lines to provide in-phase signals at the output ports, the metamaterial divider provides a 165% increase in the input return-loss bandwidth and a 155% and 154% increase in the through-power bandwidth to ports 3 and 4, respectively. In addition, the metamaterial divider is significantly more compact, occupying only 2.6% of the area that the transmission line divider occupies. The metamaterial and transmission line dividers exhibit comparable insertion losses.

Babinet Principle Applied to the Design of Metasurfaces and Metamaterials

F Falcone — 2008-06-16T07:02:36-00:00

Physical Review Letters, Vol. 93, No. 19. (1 November 2004), 197401.

Properties of left-handed metamaterials: transmission, backward phase, negative refraction, and focusing

TM Grzegorczyk — 2008-06-15T13:49:49-00:00

Microwave Theory and Techniques, IEEE Transactions on, Vol. 53, No. 9. (2005), pp. 2956-2967.

Four properties related to left-handed metamaterials are studied numerically: transmission within a stop-band, backward phase, negative refraction, and partial focusing. The unit cell of the metamaterial under study is composed of a rod and a ring originally proposed at infrared frequencies and redesigned here at microwave frequencies. We show that this ring, because of its symmetry, exhibits a better transmission in a parallel-plate waveguide than the original concentric split-ring resonator. Negative refraction is studied from a prism-shaped metamaterial, while all of the other properties are studied from a slab-shaped metamaterial. In particular, transmission and backward phase are studied on a slab where rings naturally couple with the incident wave, while partial focusing is studied on a slab of rings perpendicular to the direction of propagation. The numerical simulations are based on a two-dimensional periodic method of moments, whose Green's function is computed via Ewald's method, and a three-dimensional finite-difference time-domain technique.

Active composite right/left-handed transmission line-based mixers

J Mata-Contreras — 2008-06-13T08:39:41-00:00

Electrotechnical Conference, 2006. MELECON 2006. IEEE Mediterranean (2006), pp. 276-279.

The use of composite right/left-handed transmission lines (CRLH-TLs) in distributed mixers, instead of the usual right-handed transmission lines (RH-TLs), is explored. A simplified analysis, based on lossless transmission lines and a simple model for the active devices, shows that innovative distributed mixer designs could be achieved. In particular, it is shown that it is possible to extract the IF output from different output ports, depending on the RF frequency.

A quad-band bandpass filter using negative-refractive-index transmission-line (NRI-TL) metamaterials

M Studniberg — 2008-06-13T07:01:43-00:00

Antennas and Propagation International Symposium, 2007 IEEE (2007), pp. 4961-4964.

In this paper, we present a design for a quad-band filter that is based entirely on NRI-TL metamaterial unit cells and exhibits narrow passbands with good selectivity. The multiple passbands of these cells are exploited to provide the overall characteristics of the device. The cells are printed in microstrip, resulting in a low-profile planar device. The device can also be designed as a tri-band or dual-band filter without changing its topology.

A Compact Slot Antenna Utilizing a Right/Left-Handed Transmission Line Feed

Yu-Shin Wang — 2008-06-11T20:27:11-00:00

Antennas and Propagation, IEEE Transactions on, Vol. 56, No. 3. (2008), pp. 675-683.

A novel compact planar antenna utilizing cascaded right/left-handed transmission lines is proposed. The significance of layout planning with respect to radiation is investigated and discussed in this paper. Two segments of transmission lines of the same electrical length with opposite signs are cascaded to provide zero phase at the operation frequency. The closed-form formulas for the equivalent circuit of a transmission line are used for circuit design. Both antenna layout and radiation mechanism are discussed. For experimental demonstration, the proposed antenna operating at 2.45 GHz was implemented on an FR4 substrate. The topology using several patches has quite smaller size than the conventional patch antenna. Besides, a fairly omnidirectional radiation pattern was measured.

Investigation of a tessellated meta-material planar circuit

KW Eccleston — 2008-06-11T20:26:56-00:00

Microwave Conference, 2006. APMC 2006. Asia-Pacific (2006), pp. 927-930.

In this paper we investigate the propagation behavior of a square shaped planar meta-material guiding structure comprised of left-handed and right handed square unit cells each of the same size and arranged in a checker-board tessellation. The size of the planar structure is 19 cells by 19 cells and each cell is 8 mm by 8 mm. At 1 GHz, the left-handed unit cells have an insertion phase of 11deg and the right-handed unit cells have an insertion phase of -11deg. Both types of cells have the same Bloch impedance. The structure was fed at the centre unit cell, and there are a total of 76 peripheral ports each terminated in matched loads. At 1 GHz the power to each peripheral is equal and the phases at each port alternate between two values that differ by 11deg. Moreover, the planar structure exhibits the so-called infinite wavelength phenomenon in two dimensions and could be used in place of a circular radial power divider.