Analysis of cloaking metasurface using theory of characteristic modes

Abstract

Metasurfaces are used to design mantle cloaks based on scattering cancellation which involves surface impedance analysis. Theory of characteristic modes is a good tool for analyzing the scattering of a metallic object because it is based on surface impedance and it brings physical insight into the radiation properties of a structure without an excitation source. The theory of characteristic modes is applied in the analysis of a cylindrical cloaking metasurface used to cloak an LTE antenna to prevent it from interfering with a UMTS antenna when both antennas are co-located on the same site. The result provides a physical insight into the principle and design of mantle cloaks. It shows that degenerate resonant modes of the cloak are used to compensate for the degenerate non-resonant modes of the antenna. There is a symmetry in the modal surface current distribution of the cloak and the direction of the fundamental modal current distribution of the cloak is at 90° to that of the UMTS antenna. Also, the UMTS antenna has a better impedance matching after cloaking.