Analysis of cloaking metasurface using theory of characteristic modes

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.