Dual-Band Aperture-Shared Filtering Reconfigurable Intelligent Surfaces

Reconfigurable intelligent surfaces (RISs) have been regarded as one of the critical technologies for 6G wireless communications. Single-band RISs have received lots of attention in academia and industry, however, there are still deficiencies in the applications of multiband signals coexistence. In this article, a dual-band RIS with the capabilities of aperture-shared and filtering is presented to address these inadequacies. First, the aperture-shared schemes are investigated and analyzed, and the embedded arrangement scheme is selected. Second, the dual-band aperture-shared RIS element is designed, and two p-i-n diodes are placed on the split ring and slot-loaded patch to realize independently tunable phase shifts in the lower and higher bands. In addition, a filtering layer is designed to suppress the out-of-band interference and achieve a favorable filtering response in magnitude. Finally, an aperture-shared RIS prototype is fabricated and measured to verify independent phase shifts and filtering performance. The measured results show that 3-dB bandwidths from 4.71 to 5.14 GHz and 6.46 to 7.23 GHz are obtained. The 10-dB suppression bandwidths are achieved in the range of 4–4.56 GHz, 5.30–6.03 GHz, and 7.73–8 GHz. Moreover, independent beam scanning from 0° to 60° is realized at 4.9 and 6.8 GHz. To the best of the authors’ knowledge, the aperture-shared RIS with filtering feature is first proposed. With the advantages of dual-band independent operation and filtering response, the proposed aperture-shared filtering RIS will facilitate the spectrum management and capacity improvement of the next wireless networks.