Numerical and Equivalent-Circuit Analysis of Ultrathin FSS With Wide-Stopband Response for EM Shielding Applications

This work exhibits the design of a modified fanshaped element enclosed within a square patch featuring a circular void etched on ultrathin (0.3 mm thick) single-sided FR4 substrate, functioning as a frequency selective surface (FSS). The proposed FSS operates as a bandstop filter in the C-band covering frequencies from 3.96-7.59 GHz with shielding effectiveness (SE) of 45.7 dB. Additionally, bandpass filtering is achieved in the Sband from 2.34-3.31 GHz and in the X-band from 9.16-11.62 GHz. The ultrathin unit cell has dimensions of about 0.216λ<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf> × 0.216λ<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf> × 0.0029λ<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf>, at the lower frequency (2.95 GHz) of the passband. The polarization-insensitive FSS provides oblique angle stability of 60° with SE of about 40 dB for both TE and TM modes. The simulated results are verified through elaborated transmission line equivalent circuit model analysis.