A Compact Dual-Band Frequency Selective Surface for Concurrent 5G and 6G Applications.

In this article, a dual-band frequency-selective surface (FSS) is proposed for wireless communication systems operating in the sub-6 GHz 5G band and emerging upper-mid-band frequencies considered for future wireless applications. The proposed FSS exhibits two passbands centered at 4.8 GHz and 6.9 GHz, with corresponding reflection coefficients of -33 dB and -25 dB, respectively. The associated -10 dB impedance bandwidths extend from 4.6-5.0 GHz and 6.6-7.2 GHz, providing efficient transmission within the desired operating bands. Between these passbands, the proposed structure exhibits a band-stop response centered at 5.5 GHz, where the transmission coefficient (S21) reaches a minimum value of -40 dB over the frequency range of 5.2-5.8 GHz. This intermediate stopband suppresses unwanted signal transmission, particularly within the Wi-Fi band, thereby improving spectral selectivity and reducing potential interference in multi-band wireless communication environments. Furthermore, the proposed single-layer FSS maintains stable transmission and reflection characteristics under different polarization states and oblique incidence angles up to 60°. The measured results show good agreement with the simulated responses, demonstrating the suitability of the proposed design for applications requiring dual-band transmission and intermediate band-stop filtering in next-generation wireless communication systems.