A comparative study of cloaking of metal objects from electromagnetic pulses

摘要

The possibility of making objects invisible has always intrigued the imagination of people. The emergence of metamaterials in the 21st century has enabled the realization of devices capable of reducing the total scattering cross sections of various objects when they are illuminated by electromagnetic waves [1,2]. In this paper we study the cloaking capabilities of three different cloaking devices, namely, the transmission-line (TL) cloak [3], the metal-plate (MP) cloak [4], and the coordinatetransformation (CT) cloak [2]. When cloaking objects situated in free space, all of these devices exhibit frequency dispersion which will inevitably distort any pulse that travels within the cloaks. Since the coordinate-transformation cloak consists of an anisotropic material with some of the components of the relative permittivity and/or permeability being below 1, this cloak is inherently strongly dispersive, whereas the operation of the TL and MP cloaks is not based on resonances or resonant materials and they are thus expected to exhibit only mild dispersion.