Experimental demonstration of invisible electromagnetic impedance matching cylindrical transformation optics cloak shell

Chen, Mingji; Wang, Changxian; Cheng, Xiaodong; Gong, Congcheng; Song, Wei‐Li; Yuan, Xujin; Fang, Daining

doi:10.1088/2040-8986/aab25f

Cited by 22 publications

(8 citation statements)

References 31 publications

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“…However, for the spatial impedance, according to Equations ( 24) and ( 25), the frequency will influence both the resistance and reactance. There is a linear relation between the frequency and spatial impedance, according to Equations ( 24) and (25). Therefore, the of the magnitude of the resistance and reactance under different operating frequencies in a WPT system are proportional to the distributions shown in Figures 4(a) and (b), whereas the directions of the resistance and reactance keep the same in Figures 4(a) and (b).…”

Section: Influence Of the Frequencymentioning

confidence: 97%

“…Moreover, most researches have mentioned and used spatial impedance for a practical application. A development of an optics cloak shell via electromagnetic impedance is presented in [25], and it shows an idea to analyze different directions of impedance on one point, which means that the impedance in space is a vector but not a scaler. The researches in [26] gave a definition of the spatial impedance.…”

Section: Introductionmentioning

confidence: 99%

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Analysis on the Spatial Impedance of the Wireless Power Transfer System in the Near Field

Kang¹,

Lu²,

Xie³

et al. 2022

PIER C

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In this paper, the spatial impedance of the wireless power transfer (WPT) system is analyzed, and a resistance tunnel is found. First, the definitions of the spatial impedance in the near field are discussed, and one definition is chosen. By using this definition, the concept of the resistance and the reactance are extended from a scaler form into a vector form. Under this definition and this concept, the spatial impedance is analyzed, and a resistance tunnel is found. The tunnel possesses an obvious direction which is from the receive coil to the transmit coil, and possesses a concave phenomenon on the resistance's magnitude curves. The reason for the forming of the tunnel is also analyzed by discussing the x-and z-components of the resistance. Second, the influences on the resistance tunnel by four factors are discussed. Only the current phase difference determines the existence of the resistance tunnel. The other factors only influence the magnitude and distribution of the resistance. The correctness of the theoretical calculation is verified by implementing an electromagnetic simulation via FEM. Since the WPT system is one of the typical coupling systems in the near field, one can infer that the resistance tunnel not only exists in the WPT system, but also exists in other coupling coil systems in the near field.

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Section: Influence Of the Frequencymentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Analysis on the Spatial Impedance of the Wireless Power Transfer System in the Near Field

Kang¹,

Lu²,

Xie³

et al. 2022

PIER C

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“…Invisible cloaking is one of the most fascinating advancements in modern electromagnetic research associated with the development of metamaterials and transformation optics (TO). − Besides the high-frequency operation in microwaves or visible light, it is equally essential to investigate similar functions for low-frequency regimes where uncoupled electrical or magnetic counterparts have been explored before. − From the practice, the latter one seems more attractive as a magnetic field has been widely involved in various instrumentations, such as metal probing or nuclear magnetic resonance (NMR) imaging. In the quasi-static approximation, the bilayer cloak consisting of a ferromagnetic (FM)–diamagnetic composite has been mostly adopted to design a magnetic invisible device based on the algorithm of field “scattering” cancellation.…”

Section: Introductionmentioning

confidence: 99%

Ultrathin Conformal Magnetic Invisible Cloak for Irregular Objects

Zhan

Zhou

et al. 2021

ACS Appl. Mater. Interfaces

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Magnetic invisible cloaking has been previously demonstrated but only limited to objects with rotational geometries either in spherical or cylindrical shapes, for which the classic analytical bilayer scheme could be strictly applied to design the hiding coat. In this work, we show that a quasi-static cloaking effect could be achieved for irregular objects, e.g., metals with sharp edges, using a numerical optimization scheme. In the quasi-static limit, it is unambiguously proved that the disturbance of the irregular geometries could be well compensated by the inhomogeneous distribution of the soft ferromagnetic (FM) layer either in permeability values or in shapes under the framework of a bilayer cloak. An FM mesh coat with a constant thickness of 0.5 mm was successfully engineered to meet the specific requirements. Experimentally, good cloaking performance with a field disturbance of less than 0.5% has been achieved for a 2 × 2 × 5 cm3 brass bar in a wide frequency range from ∼10 to 250 kHz. A commercial metal scanner was also applied to verify the practical potential. The general strategy to hide almost arbitrary objects was discussed in the end. In principle, the numerical conformal coat engineered by the composite material proposed here could be broadly extended for objects with various geometries.

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“…Li et al [17] proposed radial elastic metamaterials and combined elastic wave equation and finite element model to prove that such metamaterials effectively isolated elastic waves within the bandgaps. In recent years, radial metamaterials have also been implemented to the realization of an ideal invisible cloak [18,19]. Further, excellent bandgap characteristics and unique omnidirectional wave shielding characteristics are shown in these radial metamaterials [20][21][22][23][24][25].…”

Section: Introductionmentioning

confidence: 99%

Radial seismic metamaterials with ultra-low frequency broadband characteristics

Li¹,

Jia²,

Tong³

et al. 2021

J. Phys. D: Appl. Phys.

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The metamaterials applications for protecting buildings by manipulating seismic waves, such as nuclear power plants and ancient buildings protection, have garnered considerable attention. A new type of ultra-low frequency broadband radial seismic metamaterial (RSM) has been proposed in this paper. Contrary to traditional seismic metamaterials (SMs), the proposed RSMs are arranged with radially periodic steel rings embedded in the soil. The propagation characteristics of seismic Lamb waves and surface waves in RSM are investigated. Additionally, the dispersion relations and displacement vector fields are determined by using the finite element method. As the numerical discussion, lower and wider bandgap characteristics for seismic Lamb waves and surface waves are shown in RSM in contrast to the SM. For seismic Lamb waves, the RSM with rectangular cross-section exhibits the beginning frequency of bandgaps as low as 1.6 Hz, with a bandwidth ratio of 81.27% increased by 65.33% relative to the SM in the range of 0.1-50 Hz, which is produced by the coupling between the seismic Lamb modes and local resonance; for surface waves, RSM also has a low-frequency broadband and larger relative band width of bandgap (57.5%) than the SM with the same lattice constant and filling fraction, which is caused by coupling of the overall axial resonance and Rayleigh waves mode. Furthermore, the influence of geometric parameters and material properties of RSM on bandgap characteristics is obtained. Finally, a 3D full-scale finite period model, which involves in-plane and out-of-plane modes, is designed to demonstrate the earthquake shielding performance of RSM. The proposed shielding approach could provide a better alternative in the field of seismology and related areas of ultra-low frequency vibration damping or blast protection.

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Experimental demonstration of invisible electromagnetic impedance matching cylindrical transformation optics cloak shell

Cited by 22 publications

References 31 publications

Analysis on the Spatial Impedance of the Wireless Power Transfer System in the Near Field

Analysis on the Spatial Impedance of the Wireless Power Transfer System in the Near Field

Ultrathin Conformal Magnetic Invisible Cloak for Irregular Objects

Radial seismic metamaterials with ultra-low frequency broadband characteristics

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