Personnel
Samel Arslanagic, PhD student
Olav Breinbjerg, Professor
Period
15.03.2004 - 14.03.2007.
Funding
Technical University of Denmark.
Background
Recently, an increased interest in investigating the electromagnetic properties of artificial materials, known as metamaterials (MTMs), emerged in the antenna research community. Interesting examples of the MTMs are the so-called Double Negative (DNG) materials, which are characterized by a negative real part of both the permittivity and permeability, as well as Single-Negative Materials, characterized by a negative real part of either the permittivity (the so-called Epsilon-Negative (ENG) materials) or the permeability (the so-called Mu-Negative (MNG) materials). The emphasis in this project is put on the potential use of DNG materials in the antenna technology.
Theoretical considerations related to lossless DNG materials were already performed about 30 years ago by the Russian physicist V. G. Veselago, who found that the electric and magnetic field vectors of a plane wave in such materials form a left-handed set of vectors with its wave number vector. He also found that the direction of the power flow density still forms a right-handed vector set with the field vectors, as in ordinary Double-Positive (DPS) materials, which possess a positive real part of both the permittivity and permeability. As a direct consequence of these facts, the phase and group velocities are oppositely directed in DNG materials, and therefore the interaction of such materials with electromagnetic waves, e.g., microwaves and light, exhibit a range of unusual effects including backward traveling waves, negative refraction, inverse Doppler shift, and several others.
Due to the unfamiliar electromagnetic properties of DNG materials, it is of interest to conduct a detailed study of these properties and, in particular, their application in the antenna technology.
Elements of the project
The purpose of the present project is to investigate the DNG materials and their potential applications within the field of antennas. The project consists of several elements, as described below.
1. Models and computational methods
In this part, the existing and new models of DNG materials and the methods (analytical and/or numerical) for computing the electromagnetic field interactions with these are investigated.
2. Theoretical analysis of the electromagnetic field interactions with the DNG materials
In this part, the analytical and numerical investigations of the electromagnetic wave propagation in, and scattering from, DNG materials are conducted in order to elucidate the basic mechanisms such as energy propagation, dispersion, polarization, reflection, transmission, and diffraction. A significant effort is devoted to the clarification of the sign/branch of various important parameters, such as the wave number, intrinsic impedance and refractive index in DNG materials.
3. Theoretical analysis of general and generic scattering and antenna models
In this part, the analytical and numerical investigations of general and generic scatterers and antennas utilizing DNG materials are conducted. The following models are under investigations:
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Line source illumination of single DNG cylinders,
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Line source illumination of cylindrically stratified structures involving DNG layers, either as core elements or as coatings of conventional DPS cylinders,
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Hertzian dipole illumination of a single DNG sphere,
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Hertizan dipole illumination of spherically stratified structures involving DNG layers, either as core elements or as coatings for conventional DPS spheres,
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Hertizan dipole in the presence of a half spherical shell backed with a PEC half-plane.
Lossless and lossy, as well as dispersive, DNG materials are considered. When appropriate, the use of SNG materials in the above models is likewise addressed.
The size of the structures involved in the above cases will vary from electrically small to those of which the size is comparable to the operating wavelength. In particular, considerable attention is devoted to the electrically small versions since the artificial DNG materials can form resonant structures of an almost arbitrarily small size. This remarkable resonance effect has been demonstrated by several research groups, and is further demonstrated and explored in this project for a variety of other configurations. For natural DPS materials the limits of physics makes the resonance effect impossible when the structures are electrically small but for DNG materials this is not the case.
The remarkable resonance effect suggests that DNG materials may offer a solution to antenna miniaturization. The resonance effect of small DNG structures is exemplified in Figure 1 below. This illustrates the strength of the electromagnetic field radiated by an electric line current in the presence of a cylindrical shell as obtained from an analytical solution. In Figure 1(a), the shell is made of an ordinary DPS material, and this has practically no influence on the radiation from the line current; one only notices the effect of the line current itself as though this was radiating into free space. In Figure 1(b), the shell is made of an artificial DNG material, and this is seen to cause a strong excitation of the radiated field – in this case the so-called dipolar mode. In Figure 1(c) the so-called power ratio, expressing the total radiated power for a fixed value of the line current, is shown as a function of the outer radius of the cylindrical shell.
Figure 1. Line current excitation of cylindrical shell with DPS material (a), DNG material (b), and the power (c). The DNG cylinder gives rise to a resonance effect not present for the DPS cylinder.
It is clearly seen, that the DNG shell gives rise to a resonance effect with a high radiated power – whereas the DPS shell does not. In effect, the DNG shell functions as a spatial filter selecting a particular wave mode of the line current radiated field. In the case shown here, the frequency of the electromagnetic field is 300 MHz while the diameter of the resonant DNG shell is 20mm – corresponding to just 1/50 of the free-space wavelength.
Publications
Journal publications
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S. Arslanagic, R.W. Ziolkowski and O. Breinbjerg, “Excitation of an electrically small metamaterial-coated cylinder by an arbitrarily located line source”, Microwave and Optical Technology Letters, vol. 48 (12), pp. 2598-2605, 2006.
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S. Arslanagic and O. Breinbjerg, “Electric line source illumination of a circular cylinder of lossless double-negative material: an investigation of near field, directivity, and radiation resistance”, IEEE Antennas and Propagation Magazine, vol. 48 (3), pp 38-54, 2006.
Conference publications
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S. Arslanagic, R.W. Ziolkowski and O. Breinbjerg, “Near-field distribution, directivity and differential scattering cross section for a line source-excited metamaterial-coated electrically small cylinder”, The 1st. European Conference on Antennas and Propagation (EuCAP), Nice, France, Nov. 6-10, 2006.
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S. Arslanagic, R.W. Ziolkowski and O. Breinbjerg, “Hertzian dipole excitation of higher order resonant modes in electrically small nested metamaterial shells: source and scattering results”, Proceedings of the IV International Workshop on Electromagnetic Wave Scattering - EWS, Gebze, Turkey, Sept. 18-22, 2006, pp. 8.9-8.14.
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S. Arslanagic, R.W. Ziolkowski and O. Breinbjerg, “Fundamentals of metamaterials and their applications in the design of efficient sub-wavelength radiators and scatterers”, International Student Seminar on Microwave Applications of Novel Physical Phenomena, Rovaniemi, Finland, Aug. 24-25, 2006, pp. 24-26.
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S. Arslanagic, R.W. Ziolkowski and O. Breinbjerg, “Line Source Excitation of Multilayered Metamaterial Cylinders: Source and Scattering Results”, IEEE APS Int. Symp./USNC/URSI Nat. Radio Science Meeting., Albuquerque, NM, USA, July 9-14, 2006, pp. 676-679.
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S. Arslanagic, R.W. Ziolkowski and O. Breinbjerg, “Radiated power and total scattering cross section of multilayered cylinders excited by an electric line source”, 3rd Workshop on Metamaterials and Special Materials for Electromagnetic Applications and TLC, Rome, Italy, March 30-31, 2006, p. 18.
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S. Arslanagic and O. Breinbjerg, “On sign and branch of certain parameters for simple, lossy double-negative materials”, USNC/URSI National Radio Science Meeting, Boulder, Colorado, USA, Jan. 4-7, 2006, p. 59.
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S. Arslanagic and O. Breinbjerg, “Clarification of the sign of wave number, intrinsic impedance, and refractive index for simple lossless and lossy double negative materials”, EPFL Latsis Symposium 2005, Negative Refraction: Revisiting electromagnetics from microwaves to optics, Feb. 28 – March 2, 2005, p. 78.
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S. Arslanagic and O. Breinbjerg, “Electric Line Source Illumination of Lossless Left-Handed Cylinders - A Study of Near-Field and Far-Field Properties”, Proceedings of the Turkish National URSI Committee Meeting, Bilkent University, Ankara, Turkey, 2004, pp. 19-25.
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