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Electromagnetic Wave Propagation, Radiation, and Scattering
01 Dec 1990-
TL;DR: In this article, the fundamental field equations of wave propagation in homogeneous and layered media waveguides and cavities have been studied, including the effects of a dipole on the conducting earth, inverse scattering radiometry, and interferometry numerical techniques.
Abstract: Fundamental field equations waves in homogeneous and layered media waveguides and cavities Green's functions radiation from apertures and beam waves periodic structures and coupled mode theory dispersion and anisotropic media antennas, apertures and arrays scattering of waves by conducting and di-electric objects waves in cylindrical structures, spheres and wedges scattering of complex objects geometric theory of diffraction and low fequency techniques planar layers, strip lines, patches and apertures radiation from a dipole on the conducting earth, inverse scattering radiometry, noise temperature and interferometry numerical techniques.
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TL;DR: In this paper, an exact solution for the electromagnetic field due to an electric current in the presence of a surface conductivity model of graphene is obtained in terms of dyadic Green's functions represented as Sommerfeld integrals.
Abstract: An exact solution is obtained for the electromagnetic field due to an electric current in the presence of a surface conductivity model of graphene. The graphene is represented by an infinitesimally thin, local, and isotropic two-sided conductivity surface. The field is obtained in terms of dyadic Green’s functions represented as Sommerfeld integrals. The solution of plane wave reflection and transmission is presented, and surface wave propagation along graphene is studied via the poles of the Sommerfeld integrals. For isolated graphene characterized by complex surface conductivity σ=σ′+jσ″, a proper transverse-electric surface wave exists if and only if σ″>0 (associated with interband conductivity), and a proper transverse-magnetic surface wave exists for σ″<0 (associated with intraband conductivity). By tuning the chemical potential at infrared frequencies, the sign of σ″ can be varied, allowing for some control over surface wave properties.
2,304 citations
TL;DR: Metamaterials are typically engineered by arranging a set of small scatterers or apertures in a regular array throughout a region of space, thus obtaining some desirable bulk electromagnetic behavior as mentioned in this paper.
Abstract: Metamaterials are typically engineered by arranging a set of small scatterers or apertures in a regular array throughout a region of space, thus obtaining some desirable bulk electromagnetic behavior. The desired property is often one that is not normally found naturally (negative refractive index, near-zero index, etc.). Over the past ten years, metamaterials have moved from being simply a theoretical concept to a field with developed and marketed applications. Three-dimensional metamaterials can be extended by arranging electrically small scatterers or holes into a two-dimensional pattern at a surface or interface. This surface version of a metamaterial has been given the name metasurface (the term metafilm has also been employed for certain structures). For many applications, metasurfaces can be used in place of metamaterials. Metasurfaces have the advantage of taking up less physical space than do full three-dimensional metamaterial structures; consequently, metasurfaces offer the possibility of less-lossy structures. In this overview paper, we discuss the theoretical basis by which metasurfaces should be characterized, and discuss their various applications. We will see how metasurfaces are distinguished from conventional frequency-selective surfaces. Metasurfaces have a wide range of potential applications in electromagnetics (ranging from low microwave to optical frequencies), including: (1) controllable “smart” surfaces, (2) miniaturized cavity resonators, (3) novel wave-guiding structures, (4) angular-independent surfaces, (5) absorbers, (6) biomedical devices, (7) terahertz switches, and (8) fluid-tunable frequency-agile materials, to name only a few. In this review, we will see that the development in recent years of such materials and/or surfaces is bringing us closer to realizing the exciting speculations made over one hundred years ago by the work of Lamb, Schuster, and Pocklington, and later by Mandel'shtam and Veselago.
1,819 citations
Cites methods from "Electromagnetic Wave Propagation, R..."
...The classical analytical approach for this is the Floquet-Bloch mode expansion [83-88], in which the fi elds are expanded into an infi nite sum of plane waves propagating in various directions....
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TL;DR: Wave propagation in a double negative (DNG) medium, i.e., a medium having negative permittivity and negative permeability, is studied both analytically and numerically and the DNG slab solution is used to critically examine the perfect lens concept suggested recently by Pendry.
Abstract: Wave propagation in a double negative (DNG) medium, i.e., a medium having negative permittivity and negative permeability, is studied both analytically and numerically. The choices of the square root that leads to the index of refraction and the wave impedance in a DNG medium are determined by imposing analyticity in the complex frequency domain, and the corresponding wave properties associated with each choice are presented. These monochromatic concepts are then tested critically via a one-dimensional finite difference time domain (FDTD) simulation of the propagation of a causal, pulsed plane wave in a matched, lossy Drude model DNG medium. The causal responses of different spectral regimes of the medium with positive or negative refractive indices are studied by varying the carrier frequency of narrowband pulse excitations. The smooth transition of the phenomena associated with a DNG medium from its early-time nondispersive behavior to its late-time monochromatic response is explored with wideband pulse excitations. These FDTD results show conclusively that the square root choice leading to a negative index of refraction and positive wave impedance is the correct one, and that this choice is consistent with the overall causality of the response. An analytical, exact frequency domain solution to the scattering of a wave from a DNG slab is also given and is used to characterize several physical effects. This solution is independent of the choice of the square roots for the index of refraction and the wave impedance, and thus avoids any controversy that may arise in connection with the signs of these constituents. The DNG slab solution is used to critically examine the perfect lens concept suggested recently by Pendry. It is shown that the perfect lens effect exists only under the special case of a DNG medium with $\ensuremath{\epsilon}(\ensuremath{\omega})=\ensuremath{\mu}(\ensuremath{\omega})=\ensuremath{-}1$ that is both lossless and nondispersive. Otherwise, the closed form solutions for the field structure reveal that the DNG slab converts an incident spherical wave into a localized beam field whose parameters depend on the values of $\ensuremath{\epsilon}$ and $\ensuremath{\mu}.$ This beam field is characterized with a paraxial approximation of the exact DNG slab solution. These monochromatic concepts are again explored numerically via a causal two-dimensional FDTD simulation of the scattering of a pulsed cylindrical wave by a matched, lossy Drude model DNG slab. These FDTD results demonstrate conclusively that the monochromatic electromagnetic power flow through the DNG slab is channeled into beams rather then being focused and, hence, the Pendry perfect lens effect is not realizable with any realistic metamaterial.
975 citations
TL;DR: In this paper, Dyadic Green's functions are presented for an anisotropic surface conductivity model of biased graphene, where the graphene surface can be biased using either a perpendicular static electric field or by a static magnetic field via the Hall effect.
Abstract: Dyadic Green's functions are presented for an anisotropic surface conductivity model of biased graphene. The graphene surface can be biased using either a perpendicular static electric field, or by a static magnetic field via the Hall effect. The graphene is represented by an infinitesimally-thin, two-sided, non-local anisotropic conductivity surface, and the field is obtained in terms of Sommerfeld integrals. The role of spatial dispersion is accessed, and the effect of various static bias fields on electromagnetic field behavior is examined. It is shown that by varying the bias one can exert significant control over graphene's electromagnetic propagation characteristics, including guided surface wave phenomena, which may be useful for future electronic and photonic device applications.
738 citations
Cites background or methods from "Electromagnetic Wave Propagation, R..."
...Surface Waves Guided by Graphene Pole singularities in the Sommerfeld integrals represent discrete surface waves guided by the medium [14], [15]....
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...The standard hyperbolic branch cuts [15] that separate the one proper sheet (where , such that the radiation condition as is satisfied) and the three improper sheets (where ) are the same as in the absence of surface conductivity....
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...For any planarly layered, piecewise-constant medium, the electric and magnetic fields in region due to an electric current can be obtained as [14], [15]...
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...Alternatively, the components can be obtained using the pair , where is the electric/magnetic Hertzian potential [15]....
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...The value of the wavenumbers and govern the size of , and to access upper limits for the wavenumbers it is worthwhile to represent the spectral integrals (27) as a sum of branch cuts and residues [14], [15], [18]....
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TL;DR: In this paper, a metamaterial paradigm for achieving an efficient, electrically small antenna is introduced Spherical shells of homogenous, isotropic negative permittivity (ENG) material are designed to create a resonant system for several antennas: an infinitesimal electric dipole, a very short center-fed cylindrical electric dipoles, and a coaxially-fed electric monopole over an infinite ground plane.
Abstract: A metamaterial paradigm for achieving an efficient, electrically small antenna is introduced Spherical shells of homogenous, isotropic negative permittivity (ENG) material are designed to create electrically small resonant systems for several antennas: an infinitesimal electric dipole, a very short center-fed cylindrical electric dipole, and a very short coaxially-fed electric monopole over an infinite ground plane Analytical and numerical models demonstrate that a properly designed ENG shell provides a distributed inductive element resonantly matched to these highly capacitive electrically small antennas, ie, an ENG shell can be designed to produce an electrically small system with a zero input reactance and an input resistance that is matched to a specified source resistance leading to overall efficiencies approaching unity Losses and dispersion characteristics of the ENG materials are also included in the analytical models Finite element numerical models of the various antenna-ENG shell systems are developed and used to predict their input impedances These electrically small antenna-ENG shell systems with idealized dispersionless ENG material properties are shown to be very efficient and to have fractional bandwidths above the values associated with the Chu limit for the quality factor without any degradation in the radiation patterns of the antennas Introducing dispersion and losses into the analytical models, the resulting bandwidths are shown to be reduced significantly, but remain slightly above (below) the corresponding Chu-based value for an energy-based limiting (Drude) dispersion model of the permittivity of the ENG shell
519 citations