Cloaking a metal object from an electromagnetic pulse: A comparison between various cloaking techniques

Electromagnetic cloaks are devices that can be used to reduce the total scattering cross section of various objects. An ideal cloak removes all scattering from an object and thus makes this object "invisible" to the electromagnetic fields that impinge on the object. However, ideal cloaking appears to be possible only at a single frequency. To study cloaking from an electromagnetic pulse, we consider propagation of a pulse inside a waveguide with a cloaked metal object inside. There are several ways to achieve cloaking, and in this paper, we study three such methods, namely, the coordinate-transformation cloak, the transmission-line cloak, and the metal-plate cloak. In the case of the two last cloaks, pulse propagation is studied using experimental data, whereas the coordinate-transformation cloak is studied with numerical simulations. The results show that, at least in the studied cases where the cloaked object's diameter is smaller than the wavelength, the cloaks based on transmission-line meshes and metal plates have wider bandwidth than the coordinate-transformation cloak and are thus more efficient in hiding objects from electromagnetic pulses.