Spherical Shell of ENG Metamaterial Surrounding a Dipole Antenna
In recent years, considerable interest has arisen with respect to the application of materials with negative permittivity and/or negative permeability to various electromagnetic devices. Ideal lossless and nondispersive materials with negative permittivity and permeability do not exist in nature. Artificial materials with these properties are referred to as metamaterials (Smith et al., 2000).
Recently, several papers have appeared that consider the use of a thin spherical shell of metamaterial surrounding a small dipole antenna for the purpose of improving its electrical performance (Ziolkowski and Kipple, 2003; Ziolkowski and Erentok, 2006; Tretyakov et al., 2003).
In Ziolkowski and Kipple (2003), the thin spherical shell consisted of ideal double negative material with permittivity ε = −ε0 and permeability μ = −μ0. In Ziolkowski and Erentok (2006), the spherical shell had a negative permittivity (epsilon negative or ENG material) with ; the solution for the electromagnetic field was obtained numerically.
In both of the papers mentioned above, it was found that the presence of a thin spherical shell surrounding the small dipole antenna resulted in a sharp resonance ...