Polarization insensitive multiband metasurface absorber for L, C, and X band applications

An ultrathin, multiband, polarization insensitive with wide angle stability metasurface absorber having unitcell dimension $ 0.119\lambda _{0} \times 0.119\lambda _{0} \times 0.022\lambda _{0} $ 0.119λ0×0.119λ0×0.022λ0 $ {\rm mm}^{3} $ mm3 is proposed ( $ \lambda _{0} $ λ0 is the free space wavelength at 1.6 GHz). The four-fold symmetry of the unitcell makes it insensitive to TE and TM polarizations. This metasurface follows the sub-quarter wavelength thickness including an air gap of 2.5 mm and metal backing. The proposed unitcell of the metamaterial absorber (MMA) is designed by parametric optimization and has absorption peaks in L, C, and X bands. This absorber is suitable for applications like radar cross section reduction, isolation, and stealth technologies. The lumped SMD resistors are used to enhance absorption peaks simultaneously in all bands mentioned above. This metasurface has absorptivity of 95%, 99%, 97% & 94% at 1.6 GHz, 5 GHz, 7.5 GHz and 10.2 GHz respectively. This is a polarization-insensitive absorber showing stable absorption for different incidence angles between $ 0^{\circ } $ 0∘ and $ 90^{\circ } $ 90∘ at the above-given frequencies. The absorption effect has been studied by investigating the filter effect from the equivalent circuit modeling using surface current distribution and normalized impedance. The proposed structure has been fabricated and its measurement results agree well with the simulated one.