3D-Printed Multi-Band FSS with Near-Equal Fractional Pass-/Stop-Band Divisions

This paper presents a frequency-selective surface (FSS) design fabricated by 3D printing techniques and metallization processes. The double-layer spatial filter consists of concentric resonant rings within the hexagonal unit cells, which alternately generate three passbands and two stopbands with equal fractional bandwidths (FBWs). Each passband or stopband contains two transmission poles and zeros, with sharp transitions in the roll-off regions. The tunability can be achieved by reconfiguring the dielectric insertion plate with varied effective permittivities and thickness profiles.