Ultra-thin quadri-band metamaterial absorber based on spiral structure

We introduce a design of the metamaterial absorber (MA) consisting of spiral artificial inclusions printed on an ultra-thin dielectric layer backed by a metal plate. Both simulations and experiments show that the MA can achieve absorptions up to 96.49, 94.25, 98.94 and 92.04 % at 6.69, 8.70, 11.90 and 15.14 GHz, respectively. The surface current and power loss density of each absorption frequency were discussed to reveal the physical mechanism. Moreover, the proposed quadri-band MA possesses the advantages of being ultra-thin and polarization-insensitive and thus may find potential applications.