On the Design of Frequency Selective Structure with High UHF Bandpass and C X Bandstop

Abstract

Frequency selective surface or structure (FSS), which is regarded as a kind of space filter, is widely used in the design of stealth antenna radome. In this paper, an ultra-wideband FSS with low insert loss in the radiation band and high reflection outside the band is proposed. In general, the whole FSS is composed of three SL FSS layers segregated by air spacers Equivalent circuit and formula derivation are employed to provide great insight into the low insert loss in-band and high rejection out-band. Its unit cell size is only <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\boldsymbol{0.0375\lambda_{0}\times 0.0375\lambda_{0}\times 0.125\lambda_{0}\boldsymbol{(7.5}}\mathbf{mm}\times \boldsymbol{7.5}\mathbf{mm}\times 25 \mathbf{mm}$</tex> , where <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\lambda_{0}$</tex> is the wavelength of the passband center frequency. The insert loss is simulated to be less than 1dB in the bands of 0.3~3GHz, which provides a relatively small influence on the in-band radiation. From 4 to 18GHz, the reflection coefficient is larger than 10dB. It also exerts good angular stability and polarization stability.