Switchable and optically transparent ultrawide stopband frequency selective surface for electromagnetic shielding

Abstract

Given that high frequency electromagnetic waves primarily enter buildings through windows and glass doors, there is an increasing need for switchable optically-transparent shielding with broad stopband. Herein, A novel design for a switchable and optically transparent frequency selective surface (FSS) with ultrawide-stopband is presented in this study. The structure consists of a polymethyl methacrylate (PMMA) layer sandwiched between polydimethylsiloxane (PDMS) layers which contain liquid metal microchannels arranged in an orthogonal Ω-shaped configuration. The mobility of the liquid metal allows for switching the FSS response from an all-pass to an ultrawide bandstop behavior. The proposed FSS achieves a rejection bandwidth of 18.1 GHz that covers P, L, S, C, X and Ku bands, while maintaining a transparency of 81 % and high angular stability up to 80°, regardless of polarization. Furthermore, the mechanism underlying the ultrawide stopband and high angular stability is explored through an analysis of reflection and absorption for both TE and TM polarizations. Experimental validation under both normal and oblique incidence demonstrates the ultrawide-stopband performance of the fabricated FSS.