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ABSTRACT: Narrow bandwidth significantly limits the development of electromagnetic cloaks. Here, we demonstrated both numerically and experimentally a new route to broadband low-loss electromagnetic cloak. The cloak is all-metallic and non-resonant, avoiding both the narrow bandwidth and high loss problems. To verify the proposed cloak, a sample operating at X-band was fabricated and tested. Both the simulation and experiment results convincingly confirm the broadband property of such cloaks.
Journal of Physics D Applied Physics 07/2011; 44(31):315501. · 2.54 Impact Factor
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ABSTRACT: We present a novel all-dielectric left-handed metamaterial (LHM) in the X-band microwave regime. The LHM is formed by cubes and square rods, which are made of microwave ceramic with high permittivity and low loss. Both Mie theory and dielectric resonator theory are found to play important roles in generating negative effective parameters. The effective permeability is negative in the designed frequency range due to the first Mie resonance associated with the cubes, while the effective permittivity is negative below the plasma frequency owing to the second resonance mode of the square rods. The parameter retrieval method, transmission spectra method and wedge-shaped negative refraction method are used to demonstrate that the composite has a double-negative regime. Experiments are carried out to verify the designed all-dielectric LHM. The proposed method presents new ways to realize all-dielectric LHMs.
Journal of Applied Physics 04/2011; 109(8):084918-084918-6. · 2.17 Impact Factor
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ABSTRACT: In this letter, we propose a triband second-order fre-quency selective surface (FSS). Each second-order bandpass re-sponse is realized by a three-layer patch-aperture-patch (PAP) structure. The PAP elements with different sizes are then arranged to a unit cell that is to be repeated periodically. Based on this tech- nique, an FSS unit cell with triband second-order response is de- signed. There is a respective second-order bandpass response for each operation band. The triband FSS has the merits of high selec-tivity and stable performance for incident angles within 30° and for different polarizations.
IEEE Antennas and Wireless Propagation Letters 02/2011; · 1.37 Impact Factor
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ABSTRACT: By means of area-transformation method, the material parameters of the invisible cloaks in elliptic-cylindrical and spherical coordinates were obtained. The material parameters of the invisible cloaks are nonsingular and the cloaks can operate in a wide bandwidth due to the area-transformation rather than the point-transformation. The invisible properties of the cloaks are nearly perfect when the original area is small enough compared with its counterpart in the transformed space. Full wave simulations based on finite element method verified the designed cloaks.
Journal of Applied Physics 10/2010; 108(7):073108-073108-4. · 2.17 Impact Factor
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ABSTRACT: By means of embedded optical transformation, three-dimensional diamond-shaped invisible cloaks composed of tetrahedral homogeneous blocks have been designed in this paper. The constitutive parameters of the invisible cloaks can be obtained based on the form invariance of Maxwell's equations in coordinate transformation. Numerical methods using the finite element method verified the diamond-shaped cloaks. The invisible properties of the designed cloaks are nearly perfect when the original line section is sufficiently short compared with its counterpart in the after-transformed space. The designed cloaks can operate in a wide bandwidth due to the line transformation in the coordinate transformation process.
Journal of Physics D Applied Physics 07/2010; 43(30):305501. · 2.54 Impact Factor
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ABSTRACT: The superwide-band negative refraction of the symmetrical E-shaped structure designed by Yan [Phys. Rev. E 77, 056604 (2008)] may not exist. While we accepted the validity of scattering parameter simulations completely, the process of retrieving material parameters could not be justified.
Physical Review E 04/2010; 81(4 Pt 2):048602. · 2.26 Impact Factor
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ABSTRACT: Normal-incidence left-handed metamaterials (LHMs) based on symmetrically connected split-ring resonators (SC-SRRs) were proposed and investigated numerically and experimentally. The SC-SRR, which can be easily fabricated by conventional printed circuit board technology, is composed of metallic patterns connected by metalized vias through the dielectric substrate. Under normal incidence, SC-SRR exhibits strong magnetic response, leading to negative permeability. By combing SC-SRRs with metallic wires, a normal-incidence LHM was realized. Both the simulation and experiment results demonstrated left-handed properties of the SC-SRR/wire LHM. The design method paved new ways of realizing magnetic and even electric metamaterials.
Physical Review E 03/2010; 81(3 Pt 2):036601. · 2.26 Impact Factor
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ABSTRACT: A bulk left-handed metamaterial (LHM) composed of coplanar magnetic and electric resonators was fabricated and investigated experimentally. The measurement results show a 0.5GHz wide left-handed band, which verifies the validity of the bulk LHM.
Microwave Technology and Computational Electromagnetics, 2009. ICMTCE. International Conference on; 12/2009
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ABSTRACT: By adopting the coordinate transformation theory and the corresponding numerical approach, we investigated the method of designing open cloaks that have one or more windows to exchange information and matter with the outer environment. Compared with close cloaks, open cloaks have the quasiperfect cloaking performance and are applied to any objects especially to the moving ones that must communicate and exchange matter with the outer region, which thus opens up possibilities for practical applications of cloak technologies developed recently.
Applied Physics Letters 03/2009; 94(10):103501-103501-3. · 3.84 Impact Factor
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ABSTRACT: In this letter, a novel high-directivity microstrip patch antenna (MPA) based on planar zero-index metamaterials is presented. An averaging effect over the metamaterial structure yields an effective permittivity that approaches zero at 8.75 GHz, which results in a metamaterial with zero index of refraction. Both the simulation and experimental results show that the directivity of the antenna is effectively enhanced based on the zero refraction characteristics of the metamaterial.
IEEE Antennas and Wireless Propagation Letters 02/2009; · 1.37 Impact Factor
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ABSTRACT: By using the coordinate transformation theory, we propose a media that is used to control the propagation of electromagnetic (EM) waves with the front shape and size being kept and thus to guide the wave energy along one certain direction, whatever the wave shape may be. We obtain the general formula of designing such media and present the typical example in the cylindrical EM wave case. Such media have many potential applications such as super waveguides, high direction antennas, wave-shape adapters, and other types of EM devices. The approaches presented in this paper are also applicable to acoustic waves.
Optics Letters 02/2009; 34(2):127-9. · 3.40 Impact Factor
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ABSTRACT: An effective method for designing wave shape transformers (WSTs) is investigated by adopting the coordinate transformation theory. Following this method, the devices employed to transform electromagnetic (EM) wave fronts from one style with arbitrary shape and size to another style, can be designed. To verify this method, three examples in 2D spaces are also presented. Compared with the methods proposed in other literatures, this method offers the general procedure in designing WSTs, and thus is of great importance for the potential and practical applications possessed by such kinds of devices.
Optics Express 01/2009; 16(26):22072-82. · 3.59 Impact Factor
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ABSTRACT: The approach of designing cloaks with arbitrary shapes was investigated. The coordinate transformation was considered as a homeomorphous topological mapping and the related geometrical description was proposed by introducing position surfaces and tracing lines. Then an approximation approach was presented, which considers a close shape as a polyhedron and performs the spatial compression in a general method. As an example of this approach, we deduced the material parameter equations for two-dimensional polygon cloaks and confirmed the results through numerical simulations. Our approach opens up possibilities of designing practical cloaks with arbitrary shapes through numerical or/and semi-analytical methods.
Optics Express 10/2008; 16(20):15449-54. · 3.59 Impact Factor
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ABSTRACT: The design of perfect electromagnetic cloaks is usually based on the coordinate transformation method. However, for cloaks with arbitrary shapes, it is difficult to express analytically such coordinate transformation. Thus, we have to resort to numerical methods to design approximate cloaks. In this paper, we propose a numerical method of designing cloaks with arbitrary shapes. According to this method, spatial compressions are treated as homeomorphous mappings and described in numerical forms. The corresponding coordinate transformations are therefore expressed numerically. As an application of this method, we deduced the discrete constitutive parameters of a two-dimensional polygon cloak, and verified the results by numerical simulations. This method can be also used in cases with acoustic waves and matter waves.
Physical Review E 10/2008; 78(3 Pt 2):036608. · 2.26 Impact Factor
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ABSTRACT: Based on the metamaterial cloaking technique, we propose the use of a new photon funnel to compress a plane electromagnetic (EM) wave. The theoretical analysis and numerical simulations indicate that the compression ratio can be designed optionally and the compressed wave beam remains the original wave shape without any distortions. Here we apply the method to EM waves but it can be applied to acoustic waves and other fields as well.
Applied Optics 09/2008; 47(23):4193-5. · 1.41 Impact Factor
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ABSTRACT: Using coordinate transformation stated earlier by Pendry et al. Science 312 1780 (2006)], we deduced the material parameter equation for elliptic cylinder cloaks and reported the numerical simulations as well. The theoretical and numerical results indicate that, an elliptic cylinder cloak, which is constructed with metamaterials possessing the permittivity and permeability ruled by our equation, can exclude the electromagnetic fields from the interior region without perturbing the exterior fields and therefore the objects in it can be effectively invisible to the outer region.
Phys. Rev. A. 01/2008; 77(1).
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ABSTRACT: In this paper, a polarization-dependent wide-angle three-dimensional metamaterial absorber with a near-unity absorbance was presented. The metamaterial absorber structure is composed of coplanar electric and magnetic resonators. By carefully adjusting the structural dimensions, less-than-unity ε and/or μ can be realized. To match the impedance of free space, the structural dimensions were adjusted so that ε=μ, which guarantees minimum reflection. Since the resonance-based structure is made of metallic resonators and lossy substrates, the imaginary part of refractive index is large, which guarantees strong absorption of transmitted waves. Full-wave simulations confirmed the effectiveness of the proposed three-dimensional metamaterial absorber.
Journal of Magnetism and Magnetic Materials.
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Xinhua Wang,
Shaobo Qu,
Song Xia,
Binke Wang,
Zhuo Xu,
Hua Ma, Jiafu Wang,
Chao Gu,
Xiang Wu,
Lei Lu,
Hang Zhou
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ABSTRACT: In this paper, three-dimensional (3-D) open cloaks were designed based on the coordinate transformation method. When the transformation center point is close to the boundary of the cloaks, the material parameter tensors in the near-boundary areas of the cloaks approximate to those in the background, so the near-boundary areas can be designed to be open. Full wave simulations based on finite element method verified the open cloaks we designed. Open cloaks can exchange information and materials with background media. Using the design method proposed in this paper, the boundary of open cloaks can be arbitrarily shaped, which greatly enhances the applicability of open cloaks.
Photonics and Nanostructures - Fundamentals and Applications 8(3):205-208. · 1.68 Impact Factor
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ABSTRACT: The method of designing electromagnetic invisible cloak is usually based on the form-invariance of Maxwell’s equations in coordinate transformation. By solving the partial differential equations (PDEs) that describe how the coordinates transform, three-dimensional (3-D) electromagnetic and acoustic invisible cloaks with arbitrary shapes can be designed provided the boundary conditions of the cloaks can be determined by the corresponding transformation. Full wave simulations based on finite element method verify the designed cloaks. The proposed method can be easily used in designing other transformation media such as matter-wave cloaks.
Applied Mathematics and Computation.
