A miniaturized folded square split ring resonator cell based dual band polarization insensitive metamaterial absorber for C- and Ku-band applications

In this article, a compact dual-band metamaterial absorber (MMA) is suggested for the purpose of solid materials sensing in the C- and Ku-wireless bands. The proposed MMA is formed by a basic cell based on a novel shape of the folded arms square split ring resonator (FAS-SRR).The size of the cell forming the absorber is optimized for an electrical dimension of 0.27 lambda(0 )x 0.27 lambda(0 )x 0.034 lambda(0), where lambda(0) is the free space wavelength calculated at 6.78 GHz. The physical behavior of the MMA has been explored by equivalent circuit model representing the frequency response as well as electromagnetic field analysis of the FAS-SRR. The MMA is used as a solid material sensor in both C- and Ku-bands. The material under test (MUT) is placed on the FAS-SRR patch to ahave a compact structure. The direct contact between the MMA and the MUT causes shifts in resonance frequencies in the two bands which makes the sensor more sensitive. For the MUT, we tested four materials with different permittivity ranging from 2.17 to 3.55. Simulation results show that the MMA has polarization-insensitive absorption with incident angle stability up to 45 degrees for both transverse electric (TE) and transverse magnetic (TM) modes. The proposed MMA absorbs in the C- and Ku-band with two absorption peaks near-unity; one of them is located for an absorption coefficient of 91.73% at 6.78 GHz. The second absorption rate of 99.97% is located in the Ku-band at 13.92 GHz. The proposed MMA shows good detection qualities with a sensitivity of 4.62% (800 MHz frequency shift) at the lower band and 4.53% (1610 MHz frequency shift) at the upper band. All these absorption and sensing qualities of the proposed MMA with unique shape make it a potential candidate for solid materials sensing in microwave frequency spectrum.