Wideband Reconfigurable Intelligent Surface Using Dual-Resonance Element

Reconfigurable intelligent surfaces (RISs) are regarded as one of the critical technologies for the next generation of wireless communication. However, the bandwidth extension of RIS remains an important challenge that needs to be overcome. In this letter, a method of enhancing the RIS bandwidth by using the dual-resonance element is presented. The element is composed of a dumbbell-shaped patch and a split ring patch, which can achieve a phase shift range of greater than 360° in a wide frequency range. Moreover, an approach to improving phase shift linearity is proposed. Finally, a RIS array is designed, simulated, and fabricated to verify the broadband improvement. The measured results coincide well with the simulated ones, showing that the main beam can be scanned up to ±60° and the measured 3 dB gain bandwidth is 13.1% from 4.65 to 5.3 GHz, which is helps in wideband wireless communication.