Wideband and Wide-Angle Switchable Spatial Filter/Shielding With Polarization-Independent Response

In this letter, an active second-order frequency-selective surface that features a switchable wide pass-band is proposed. Compared to other multilayer feeding structures, only one layer of frequency-selective surface (FSS) is elaborately reconfigured in this design, whose full planar symmetry structure is not destroyed, to achieve the desired all-polarized controlled behavior. The presented design provides good responses under different incident angles and polarizations. The fulfilled structure is composed of three FSS layers and is controlled by semiconductor switches. When the switches are in
off
-state, the proposed design acts as a high-transmittance second-order filter with a low ripple level, whose −0.5 dB passband width is over 24.4% and minimum insertion loss is only 0.1 dB. By switching the semiconductors to
on
-state, the unit cells of the top FSS layer are short-connected, which leads to an ultrawideband shielding behavior from 0 to 10 GHz. Moreover, the proposed structure presents consistent responses under 0°–90° rotation polarizations. Both filter and shielding responses can be obtained up to the 60° incidence. Finally, a prototype is fabricated and measured, and the desired wideband, high-efficiency, wide-angle, and polarization-insensitive switchable performances are obtained through equivalent-circuit calculations, numerical simulations, and experimental measurements.