Incident Angle Stable Broadband Conformal mm-Wave FSS for 5G (n257, n258, n260, and n261) Band EMI Shielding Application

This letter presents a conformal, polarization insensitive high angular incident angle (AIA) stable broadband bandstop mm-wave frequency selective surface (FSS) for 5G (n258, n257, n260, and n261) band electromagnetic interference (EMI) shielding application. Coupled resonators are designed on the back-to-back side of a thin dielectric substrate to achieve broad bandstop features. The top fractal resonator realizes the lower stopband (S-21<-10 dB) and makes the FSS unit cell size of 0.24 lambda(0), where lambda(0) is the lower stopband frequency. The FSS geometry offers a -10 dB transmission coefficient (S-21) within the range of 23.96-45.92 GHz, resulting in a percentage bandwidth (%BW) of 62.85%, effectively covering the desired 5G band. The polarization insensitivity and high AIA stability up to 60 degrees are achieved by symmetric rotational geometry of the resonators and compact unit cell size, respectively. In addition, the thin profile of the FSS makes it suitable for conformal applications. To verify the proposed FSS, a prototype is fabricated and measured considering normal and conformal conditions. The simulated and measured results are found to be consistent. Therefore, the proposed FSS has the merits of EMI shielding application at 5G mm-wave applications.