Design and demonstration of a 2.5D frequency-selective surface for sub-6 GHz 5G wireless communication

This paper presents an ultraminiaturized bandstop closed-loop 2.5D frequency-selective surface (FSS) for sub-6 GHz 5G wireless communication. Four metallic vertical vias interconnect metallic elements present on both sides of the substrate to form a modified closed-loop design. The proposed structure band stops the entire sub-6 GHz 5G band (C-band/NR N78 band/LTE 42/43 band) ranging from 3.2 to 3.9 GHz with a resonant notch at 3.62 GHz. This design supports polarization insensitivity and procures maximum relative deviation of 0.5% and 0.2% at 80 degrees incident transverse electric (TE) and transverse magnetic (TM) polarized waves, respectively. The proposed FSS prototype has been fabricated and tested. Experimentally, the resonant notch is obtained at 3.55 and 3.68 GHz under TE and TM normal incident polarized waves, respectively. Moreover, good agreement in the frequency response curves is observed between simulated and measured results. The proposed unit cell is 3.6 x 3.6 mm(2) in dimensions, which is 0.04 lambda x 0.04 lambda, where lambda is the resonant wavelength.