Hepta-Band Ultra-Thin Metasurface Absorber for S-, C-, X-, Ku-, and K-Band Applications

This article presents a metasurface absorber demonstrating high absorption performance in the microwave range. The proposedabsorber operates in theS-,C-,X-,Ku-,andK-band frequencies, achieving over 90% absorption at seven differentfrequency points. The peak absorption frequencies of the absorber are 2.8, 6.32, 9.17, 12.21, 14.4, 17.3, and 19.5 GHz,with absorption performances of 92.6, 91.7, 93, 96.3, 97.4, 98.3, and 99.8%, respectively. The metasurface is printed on aneconomical FR-4 substrate, and the unit cell size is designed to be very thin, measuring 0.146 lambda(o)x0.146 lambda(o)x0.0093 lambda(o )in termsof the maximum wavelength. The design consists of four different resonators, each with a symmetric structure, which makesthe design polarization insensitive for both transverse electric (TE) and transverse magnetic (TM) modes. When examiningthe absorber's performance at oblique angles, it was observed that, except for the third peak point, the other six peak pointsmaintain absorption performance above 80% up to 45 degrees. At the third peak point, the absorption performance is around65% at 45 degrees. To better understand the absorption mechanism, the characteristic impedance, permittivity, permeability,surface current, electric and magnetic field distribution graphs of each resonator were analyzed. To verify the reliability of thesimulation results, the design's equivalent circuit model (ECM) was created using the ADS circuit simulator. The monostaticRCS of the design was investigated, and it was found to exceed 7 dBsm at the absorbing frequencies. Additionally, a prototypeof the proposed special metasurface absorber was fabricated, and experimental absorption performance was obtained. Theprototype measurement results were found to be quite consistent with the simulation results.