Frequency selective surface design with multifunction response for multibands

The active frequency selective surface (AFSS), which can switch between five bands and has multifunctional response, is novel inclusion in the spatial filters domain. The proposed AFSS consists of double orthogonal metal layers disposed on two sides of a substrate. This active structure adopts a four-bit scheme with embedded parallel bias lines used to feed four PIN diodes. The nine independently controllable combinations procure nine different frequency responses. The operating nine combinations switch between five bands centered at frequencies of 1.54 GHz, 2.21 GHz, 2.94 GHz, 2.99 GHz and 3.2 GHz, which have corresponding fractional bandwidths of 18.3%, 26.6%, 12.1%, 8.4% and 1.3%, respectively. These frequencies cover the two, polarization and electromagnetic, switching functions. This multiband and multifunctional design also achieves reasonable angular stability without spurious resonances. Justification to how the proposed design works is provided through surface current distribution, electric field intensity and equivalent circuit model. The simulated multiband design is fabricated and proved its authenticity by the free space measurements scheme.