Multiband polarisation insensitive metamaterial absorber based on circular fractal structure

In this study, the authors present a geometrically symmetrical fractal structure called circular fractal structure. The iterative process of the geometric construction is illustrated and the dimension of the proposed circular fractal structure is 1.5729 based on the similarity dimension. Then, a polarisation insensitive multiband perfect metamaterial absorber (MMA) is proposed based on the circular fractal structure. The proposed MMA has three near-perfect absorption bands for both transverse electric (TE) and transverse magnetic (TM) polarisations based on the theory of the fractal geometry. The current distribution on the top and bottom surfaces of the MMA are presented to preferably understand the physical mechanism behind the multiband absorption. The simulated results match the experimental results well. For both TE and TM polarisations, the three absorption frequencies are f₁ = 2.29 GHz, f₂ = 4.28 GHz, and f₃ = 11.71 GHz, with the absorptivity of 98.7, 99.4, and 99.5%. Both experimental and simulated results indicate that the proposed circular fractal MMA is a promising candidate for absorbing elements in scientific and military applications.