High-Selectivity FSS with Wide Stopbands for EMI Suppression in Wireless Power Transfer Systems

A novel frequency selective surface (FSS) with a high-selectivity passband and two wide stopbands for electromagnetic interference (EMI) suppression in wireless power transfer (WPT) systems is proposed in this letter. The proposed FSS consists of a second-order bandpass layer and a bandstop layer. The bandpass layer provides the initial frequency filtering property while the bandstop layer is utilized to improve the frequency selectivity and EMI suppression performance. The equivalent circuit models (ECMs) of the two layers are discussed respectively to better explain the working mechanism. A prototype of the proposed FSS is fabricated and measured. Measured results show that the proposed FSS has a high-selectivity 3 dB passband from 25.85 GHz to 29.75 GHz, which covers the 5G n257 band. Meanwhile, the EMI suppression band with shielding effectiveness over 20 dB covers from 11.88 GHz to 23.81 GHz and 30.85 GHz to 41.64 GHz. Compared with existing works, the proposed FSS realizes significant enhancement of both frequency selectivity and out-of-band EMI suppression and is a good candidate for EMI suppression in WPT systems.