An ultra-broadband flexible polarization-insensitive microwave metamaterial absorber

In this paper, an ultra-broadband flexible polarization-insensitive microwave metamaterial absorber is proposed, characterized, and fabricated. To achieve high broadband absorption, a two-layer periodic indium-tin-oxide (ITO) patches array printed on polyethylene terephthalate (PET) dielectric layers is used to generate high ohmic loss. The simulation results show that the proposed absorber can achieve greater than 90% absorption in the microwave band range of 19.68 to 94.7 GHz. The absorber is polarization-insensitive due to the symmetry of the structure with high absorption over a wide incidence angle of 60°. The mechanism of ultra-broadband absorption is discussed by the impedance matching theory, the surface current distribution, and the electric field distribution. In addition, the equivalent circuit model is utilized to analyze the effect of the structural parameters. Furthermore, the bow-frame method validates that the experimental measurements are consistent with the simulated spectra. With advantages of absorption of ultra-broadband, polarization-insensitivity, and flexibility, the proposed absorber facilitates its use in numerous potential applications for energy harvesting, imaging and sensing, stealth technology, modulating, and so on.