Abstract
A ground-plane cloak is designed based on the quasi-conformal mapping method to hide a perfectly conducting object. It is fabricated with a metamaterial, a mixture of a dielectric and air. Using the dielectric mixing formula, the required volume fraction is calculated for a designed refractive index of the cloak. To guarantee the statistical isotropy of the cloak structure, many small pixels are randomly connected to form the metamaterial. A three-dimensional printing machine is used to implement the whole designed cloak structure. The performance of the cloak is experimentally analyzed over a wide frequency range for both independent polarizations. The measurement is also validated by numerical full-wave simulations. Because the quasi-conformal mapping generates unrealistic refractive indices, less than unity, those are removed. The effect of the truncation is experimentally observed and theoretically analyzed by the ray-tracing method.
Highlights
Because a metamaterial can be synthesized to provide any electromagnetic properties that do not exist in nature[1], metamaterials have been studied in the last decade and applied to many electromagnetic applications such as antennas, absorbers, lenses, and cloaking devices[2,3,4,5]
To implement the designed refractive index profile, metamaterial has usually been used because it can be fabricated with arbitrary relative permittivity or permeability
The quasi-conformal mapping (QCM) generates a relative permittivity profile depending on the shape of the object hidden by the ground-plane cloak while the permittivity is fixed as unity
Summary
Because a metamaterial can be synthesized to provide any electromagnetic properties that do not exist in nature[1], metamaterials have been studied in the last decade and applied to many electromagnetic applications such as antennas, absorbers, lenses, and cloaking devices[2,3,4,5]. The cloak medium is inhomogeneous, and its relative permittivity or refractive index profile can be generated by the transformation optics (TO) technique[6,7,8]. The TO technique is based on the coordinate transformation, which changes the electromagnetic wave propagation path inside the medium by varying the refractive index. To implement the designed refractive index profile, metamaterial has usually been used because it can be fabricated with arbitrary relative permittivity or permeability. Many metamaterials are design based on a resonance phenomenon This kind of metamaterial has the advantage of implementing very high relative permittivity. The QCM generates a relative permittivity profile depending on the shape of the object hidden by the ground-plane cloak while the permittivity is fixed as unity. Synthesized by mixing dielectrics with different relative permittivities. The characteristic of the meta-cell is experimentally analyzed[27]
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