An Ultra-thin Flexible Double-Layer Dual-Band Frequency Selective Surface

An ultra-thin double-layer frequency selective surface (FSS) with dual-band pass is presented. The proposed FSS is composed of two different metallic surfaces, separated by a 0.1-mm polymide (PI) dielectric layer, achieving two transmission bands. The FSS has high frequency selectivity and flexibility benefits from its ultra-thin, double-layer FSS structure. Two transmission center frequencies are 5.85 GHz and 15.86 GHz, and the insertion loss is extremely low, around 0.10 dB and 0.22 dB. The transmission bandwidths with transmission coefficients larger than −3 dB are 1.77 GHz and 1.78 GHz, respectively. The overall thickness is 0.136 mm, less than 0.003 \({\lambda }_{0}\), where \({\lambda }_{0}\) is the free-space wavelength at the first resonant frequency. The operating principle of the proposed FSS is analyzed using an equivalent circuit model. Finally, a prototype has been fabricated and measured, the measured result being in good agreement with the simulated result.