Broadband metamaterial microwave absorber for X-Ku band using planar split ring-slot structures

Abstract

In this paper, a broadband metamaterial microwave absorber was designed and fabricated. Five unit cells of different geometrical dimensions which were designed using CST simulator, achieved at least 80% absorption of microwave at 11 GHz, 12 GHz, 13 GHz, 14 GHz and 15 GHz, respectively. The proposed metamaterial absorbers unit cell was composed of a split ring resonator and a microstrip slot structure, which was printed in repeated pattern on both sides of FR-4 substrate with 1.58 mm and (20×20) cm2 of thickness and area, respectively. In this study, the designed microstrip slot structure contains multi-width section compared to a conventional linear slot structure. Parametric studies of the geometrical dimensions for the metamaterial absorber were observed and analysed. The size of the unit cell decreased by 7% in average which caused the shifting of absorption peak from lower to higher frequency by 1 GHz. The metamaterial absorbers were experimentally tested using free-space measurement technique covering X-Ku band in which the planar surface of the metamaterial absorber was normal to the incident wave (in-plane). The S-parameters measurement results showed that the absorption properties of the metamaterial for normal incidence case (in-plane) were slightly deviate from the simulation results by shifting 0.3 GHz to higher frequency.