Comparison between Frequency Selective Surfaces with Rectangular and Hexagonal Periodicity Operating as Absorbers

Two frequency selective surfaces operating as absorbers, with rectangular and hexagonal periodicity respectively, and relying on the same metal pattern in the unit cell are compared. The structures are implemented on an FR4 substrate, covered with copper metallization. The frequency responses (reflection coefficient) in normal incidence of electromagnetic waves and contents of higher order modes in the two cases are compared. Finally, the frequency response in oblique incidence of the hexagonal array is reported.