Calculation of Inductance, Capacitance, and Microwave Absorbance of Modified Square Loop Frequency Selective Surface

The square loop (SL) is the typical pattern of a frequency selective surface (FSS) with high inductance (L) and capacitance (C). In this study, modified patterns including split square loop FSS (SSL-FSS) and I-type FSS (I-FSS) are proposed, and their L and C values were estimated using the equivalent circuit model. The insertion of an air gap in the SL conductor stripes decreased both L and C, due to the reduction in stripe length. Meanwhile, when I-FSS was polarized in parallel with an electric field, it had the effect of reducing stripe width and, thereby, exhibited a higher value of L. Using the retrieved L and C values, microwave absorbance can be determined in the three-layer structure composed of FSS on a grounded dielectric substrate. The simulation results obtained with computational tool provided almost the same reflection loss result, which indicates that the equivalent circuit approach is reliable and efficient for determining the L, C values of various FSS.