Stacked lightweight metasurfaces for wider stopband in X-K band

Abstract

Frequency selective surfaces printed on optically transparent, large-area, flexible plastic sheets are studied for their passband and stopband characteristics when present as single-layer, two-layer and three-layer stacks. The unit cell design, its size, spacing and thickness on the substrate enable the single layer metasurface to yield a stopband width of 4.46 GHz (corresponding to 34.80%), when the center frequency is at 12.83 GHz in simulation and 12.86 GHz in measurement. On stacking identical surfaces as two-layer and three-layer configurations with suitable displacements both within the surface plane and perpendicular to the surface plane, the structural geometry of the unit cell gets varied leading to an ultra-wide stopband of 8.96 GHz in the range from 12.16 GHz to 21.11 GHz which covers X to K band. This leads to a wider stopband width of 43.60% for two-layer stack and 48.10% for three-layer stack with no in-plane shift. This is further enhanced to 65.50% with suitable shift within the plane of the stacked design. The three-layer stacked structure is ultra-thin with a thickness of 0.012 λ0. The single layer as well as all the three stacked structures have stopband characteristics that are invariant to incidence angle variation up to 750.