Ultra-thin electromagnetic cloak for hiding a metallic obstacle from antenna radiation at low frequency

We demonstrate numerically and experimentally the feasibility of an ultra-thin invisibility cloak for low frequency antenna applications. We consider a monopole antenna mounted on a ground plane and a metallic obstacle located in its near-field. We simulate the real antenna radiation scenario considering the finite size of the obstacle, its cylindrical form, as well as the non-negligible influence of the ground plane. To restore the radiation patterns of the antenna perturbed by an obstacle we propose here an electromagnetic cloak that consists simply of metallic patches separated from the obstacle by a dielectric substrate. We show that the radiation patterns of the monopole antenna can be restored completely owing resonant electromagnetic modes localized under the patch. The thickness of the coverage of the obstacle is close to λ/240. The dimensions of the patch are determined by the frequency and the dielectric permittivity of the substrate. To demonstrate experimentally the concept, we fabricate and characterize a prototype at 125MHz using classical printed board technology. The measurements are in excellent agreement with the simulations and demonstrate the efficiency of the cloak.