Sub-Wavelength Polarization-Independent Frequency Selective Surface for X-band Shielding

A sub-wavelength polarization independent frequency selective surface (FSS) is presented for X-band shielding. The FSS unit cell constructed from a split ring slot on a circular conductive patch with symmetrical axis orientation angle of 45° that coupled to another identical one within a FR4 dielectric substrate to selectivity enhancement and shielding bandwidth adjustment. The size of the proposed FSS unit cell is 0.3λ
₀
×0.3λ
₀
, where λ
₀
is the center frequency (10 GHz) wavelength at the free space. This FSS present more than 25dB attenuation at the shielding band and a great angle independence up to 60°. Finally, by comparing the simulated results of the full-wave and measurement amount acquired by waveguide method, the performance of the FSS at the bandstop frequency range is validated.