Characteristic impedance modelling of circular loop and square loop frequency selective surface (FSS) on hybrid material

An impedance modeling for a unit cell of the circular loop and square loop FSS structure is presented in this paper. The unit cell of the circular loop and square loop FSS are designed and simulated using the CST Microwave Studio software at 2.4 GHz based on industrial, scientific and medical bands (ISM). The design FSS structure consists of FSS structures placed on the FR4 and glass. The reflection (S11) and transmission (S21) of the design FSS structure is analyzed based on the six types of configuration that have been set up. The hybrid material (FR4 and glass) effect the transmission and reflection signal of the FSS. The highest efficiency for circular loop FSS and square loop FSS are 91.4% and 88.1% with a return loss of -25.31 dB and -18.72 dB by using configuration 1. The frequency response of the FSS is shifted to the lower part when the hybrid materials are used. So, the size of the FSS can be reduced by using hybrid materials to achieve the desired frequency response.