Polarization-Independent, Thin, Broadband Metamaterial Absorber Using Double-Circle Rings Loaded with Lumped Resistances

We present a broadband and polarization-insensitive metamaterial absorber (MA) composed of a dielectric substrate sandwiched with double-circle rings (DCRs) and welded with lumped resistances and continuous metal film. The structure is designed with thickness of 3 mm and investigated by simulation, fabrication, and experiment. The results show that the composite MA loaded with lumped resistances has wider absorptivity compared with a structure with only DCRs. The simulation results indicate that the proposed absorber achieves 7.60-GHz-wide absorption from 8.87 GHz to 16.47 GHz with absorptivity greater than 90%, in excellent agreement with experimental results. Further simulations indicate that there exist optimal values for the lumped resistances for which the absorptivity is the highest and the bandwidth widest. Additionally, the proposed MA is polarization insensitive at normal incidence. Simulation results for wide angles of incidence of both transverse electric and transverse magnetic waves are also investigated.