A Quad-Band Polarization Insensitive Metamaterial Microwave Absorber

A novel concept for quad-band metamaterial microwave absorber for C, Ku, Ka and V band application is proposed. The suggested absorber's unit cells are constructed from a FR4-epoxy substrate with a 0.5 mm thickness, an LC electric resonator, and a back-end ground plate. Two concentric square rings and a slotted circular ring make up the unit cell construction. The return loss (
$S_{11}$
) is used to determine the medium's ideal characteristics, and the EM behavior is utilized to explain how a unit cell functions. The minimized dimension of the unit cell is
$0.1\lambda_{0}\text{mm} \times 0.1 \lambda_{0}\text{mm}\times 0.0126 \lambda_{0}\text{mm}$
, where
$\lambda_{0}$
is the wavelength of free space corresponding to the absorption peak at the lowest frequency of 7.6 GHz. Four absorptivity peaks greater than 92%,99%, and 95%,92% occur at frequencies 7.6 GHz, 18.69GHz, 33 GHz and 51.56 GHz respectively and having FWHM bandwidth of 400 MHz (7.42-7.82 GHz), 910 MHz (18.24-19.15 GHz), 1.77 GHz (32.09-33.86 GHz) and 3.86 GHz (49.95-53.81 GHz) corresponds to the maximum absorption frequencies for normal incidence are visible in the simulated outcome. The designed structure is insensitive to polarization and having stable TE and TM mode absorptivity curve for oblique incidences up to 75° for 1–40 GHz frequency band; hence the same structure behaves as triple-band absorber for oblique incidences.