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C M Soukoulis - One of the best experts on this subject based on the ideXlab platform.
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Electromagnetic Parameter retrieval from inhomogeneous metamaterials
Physical Review E, 2005Co-Authors: David R Smith, D C Vier, Th Koschny, C M SoukoulisAbstract:We discuss the validity of standard retrieval methods that assign bulk Electromagnetic properties, such as the electric permittivity « and the magnetic permeability m, from calculations of the scattering sSd Parameters for finite-thickness samples. S-Parameter retrieval methods have recently become the principal means of characterizing artificially structured metamaterials, which, by nature, are inherently inhomogeneous. While the unit cell of a metamaterial can be made considerably smaller than the free space wavelength, there remains a significant variation of the phase across the unit cell at operational frequencies in nearly all metamaterial structures reported to date. In this respect, metamaterials do not rigorously satisfy an effective medium limit and are closer conceptually to photonic crystals. Nevertheless, we show here that a modification of the standard S-Parameter retrieval procedure yields physically reasonable values for the retrieved Electromagnetic Parameters, even when there is significant inhomogeneity within the unit cell of the structure. We thus distinguish a metamaterial regime, as opposed to the effective medium or photonic crystal regimes, in which a refractive index can be rigorously established but where the wave impedance can only be approximately defined. We present numerical simulations on typical metamaterial structures to illustrate the modified retrieval algorithm and the impact on the retrieved material Parameters. We find that no changes to the standard retrieval procedures are necessary when the inhomogeneous unit cell is symmetric along the propagation axis; however, when the unit cell does not possess this symmetry, a modified procedure—in which a periodic structure is assumed—is required to obtain meaningful Electromagnetic material Parameters. DOI: 10.1103/PhysRevE.71.036617
David R Smith - One of the best experts on this subject based on the ideXlab platform.
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Electromagnetic Parameter retrieval from inhomogeneous metamaterials
Physical Review E, 2005Co-Authors: David R Smith, D C Vier, Th Koschny, C M SoukoulisAbstract:We discuss the validity of standard retrieval methods that assign bulk Electromagnetic properties, such as the electric permittivity « and the magnetic permeability m, from calculations of the scattering sSd Parameters for finite-thickness samples. S-Parameter retrieval methods have recently become the principal means of characterizing artificially structured metamaterials, which, by nature, are inherently inhomogeneous. While the unit cell of a metamaterial can be made considerably smaller than the free space wavelength, there remains a significant variation of the phase across the unit cell at operational frequencies in nearly all metamaterial structures reported to date. In this respect, metamaterials do not rigorously satisfy an effective medium limit and are closer conceptually to photonic crystals. Nevertheless, we show here that a modification of the standard S-Parameter retrieval procedure yields physically reasonable values for the retrieved Electromagnetic Parameters, even when there is significant inhomogeneity within the unit cell of the structure. We thus distinguish a metamaterial regime, as opposed to the effective medium or photonic crystal regimes, in which a refractive index can be rigorously established but where the wave impedance can only be approximately defined. We present numerical simulations on typical metamaterial structures to illustrate the modified retrieval algorithm and the impact on the retrieved material Parameters. We find that no changes to the standard retrieval procedures are necessary when the inhomogeneous unit cell is symmetric along the propagation axis; however, when the unit cell does not possess this symmetry, a modified procedure—in which a periodic structure is assumed—is required to obtain meaningful Electromagnetic material Parameters. DOI: 10.1103/PhysRevE.71.036617
Th Koschny - One of the best experts on this subject based on the ideXlab platform.
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Electromagnetic Parameter retrieval from inhomogeneous metamaterials
Physical Review E, 2005Co-Authors: David R Smith, D C Vier, Th Koschny, C M SoukoulisAbstract:We discuss the validity of standard retrieval methods that assign bulk Electromagnetic properties, such as the electric permittivity « and the magnetic permeability m, from calculations of the scattering sSd Parameters for finite-thickness samples. S-Parameter retrieval methods have recently become the principal means of characterizing artificially structured metamaterials, which, by nature, are inherently inhomogeneous. While the unit cell of a metamaterial can be made considerably smaller than the free space wavelength, there remains a significant variation of the phase across the unit cell at operational frequencies in nearly all metamaterial structures reported to date. In this respect, metamaterials do not rigorously satisfy an effective medium limit and are closer conceptually to photonic crystals. Nevertheless, we show here that a modification of the standard S-Parameter retrieval procedure yields physically reasonable values for the retrieved Electromagnetic Parameters, even when there is significant inhomogeneity within the unit cell of the structure. We thus distinguish a metamaterial regime, as opposed to the effective medium or photonic crystal regimes, in which a refractive index can be rigorously established but where the wave impedance can only be approximately defined. We present numerical simulations on typical metamaterial structures to illustrate the modified retrieval algorithm and the impact on the retrieved material Parameters. We find that no changes to the standard retrieval procedures are necessary when the inhomogeneous unit cell is symmetric along the propagation axis; however, when the unit cell does not possess this symmetry, a modified procedure—in which a periodic structure is assumed—is required to obtain meaningful Electromagnetic material Parameters. DOI: 10.1103/PhysRevE.71.036617
Zhongguo Song - One of the best experts on this subject based on the ideXlab platform.
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calculation of effective Electromagnetic Parameters of multi needle zinc oxide whisker based on equivalent spherical particle and strong fluctuation theory
Journal of Applied Physics, 2014Co-Authors: Yuchen Zhao, Jiangfan Liu, Zhongguo SongAbstract:Multi-needle zinc oxide whisker (M-ZnOw) includes tetrapod-needle ZnOw (T-ZnOw), flower-shaped ZnOw, and other similar ZnOw architectures. The unique three-dimensional (3D) and multi-needle-shaped structures give the special performance of M-ZnOw, but make it difficult to calculate the effective Electromagnetic Parameters of M-ZnOw composites. In this paper, based on the equivalent spherical particle and the strong fluctuation theory, three different closed-form expressions are presented to calculate the effective Electromagnetic Parameters of M-ZnOw composites. To start with, because of the macroscopic isotropic nature of M-ZnOw composites and lossy properties of M-ZnOw itself, an equivalent spherical particle is introduced in the scheme to simplify the unique microscopic structures of M-ZnOw, and the possible limitations of the presented equivalent spherical particle are discussed qualitatively. In addition, different closed-form expressions to calculate the effective Electromagnetic Parameter are obtained by means of representing the physical situations of conductive network as different correlation functions in the strong fluctuation theory. Finally, the effective permeability of a T-ZnOw/Fe – paraffin composite is calculated by these three expressions in 2–18 GHz frequency range. Very good agreement between the calculated and experimental results on one hand verifies the rationality of presented expressions, and on the other hand indicates that the correlation function plays an important role in improving the performance of the presented expression.
D C Vier - One of the best experts on this subject based on the ideXlab platform.
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Electromagnetic Parameter retrieval from inhomogeneous metamaterials
Physical Review E, 2005Co-Authors: David R Smith, D C Vier, Th Koschny, C M SoukoulisAbstract:We discuss the validity of standard retrieval methods that assign bulk Electromagnetic properties, such as the electric permittivity « and the magnetic permeability m, from calculations of the scattering sSd Parameters for finite-thickness samples. S-Parameter retrieval methods have recently become the principal means of characterizing artificially structured metamaterials, which, by nature, are inherently inhomogeneous. While the unit cell of a metamaterial can be made considerably smaller than the free space wavelength, there remains a significant variation of the phase across the unit cell at operational frequencies in nearly all metamaterial structures reported to date. In this respect, metamaterials do not rigorously satisfy an effective medium limit and are closer conceptually to photonic crystals. Nevertheless, we show here that a modification of the standard S-Parameter retrieval procedure yields physically reasonable values for the retrieved Electromagnetic Parameters, even when there is significant inhomogeneity within the unit cell of the structure. We thus distinguish a metamaterial regime, as opposed to the effective medium or photonic crystal regimes, in which a refractive index can be rigorously established but where the wave impedance can only be approximately defined. We present numerical simulations on typical metamaterial structures to illustrate the modified retrieval algorithm and the impact on the retrieved material Parameters. We find that no changes to the standard retrieval procedures are necessary when the inhomogeneous unit cell is symmetric along the propagation axis; however, when the unit cell does not possess this symmetry, a modified procedure—in which a periodic structure is assumed—is required to obtain meaningful Electromagnetic material Parameters. DOI: 10.1103/PhysRevE.71.036617