A Dual-Polarization AFSS With Stealth and Transparency Integrated

The active frequency selective surface (AFSS) has attracted extensive attention for its frequency selection and reconfigurability characteristics in radome designs. This letter presents a three-layer dual-polarization AFSS with spiral and interdigital <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> resonators, where p-i-n diodes and lumped resistors are loaded. The total thickness is 8.962 mm (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.138~\lambda $</tex-math> </inline-formula>) and unit cell periodicity is 8 mm (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.124~\lambda $</tex-math> </inline-formula>). According to the equivalent circuits, the operational principle is analyzed. The full-wave simulation results are presented, which show thatthestructure exhibits a switchable band centered in the X-band. The 3 dB transmission band is from 8.85 to 9.79 GHz in <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> state and the working band is from 4.61 to 13.20 GHz (96.5%) which achieves absorption on both sides. In <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> state, the absorption band (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S_{21}$</tex-math> </inline-formula>, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S_{11} \lt -10$</tex-math> </inline-formula> dB) is from 4.10 to 11.35 GHz (93.9%). The above results are verified by testing the fabricated samples and it exhibits stable performance under oblique incidence at 30°.