High-capacitive frequency selective surfaces of folded spiral conductor arrays

A high-capacitive frequency selective surface (FSS) is proposed with the aim of achieving a small array periodicity composed of four folded arms spiral conductors with 90 degrees rotation symmetry. The electromagnetic response of the proposed FSS can be analyzed by an equivalent circuit model where the circuit parameters (L, C) are dependent on the geometries of conductors. A high value of capacitance was predicted arising from the inter-plane and intra-plane couplings between the folded spiral conductors distributed over large effective segments with a small gap spacing. However, the value of the total equivalent inductance decreases due to the parallel circuit connection of the shunted inductance of each arm. Parametric analysis on the geometrical effect was also conducted to validate the applied equivalent circuit model.