A 2-bit Polarization-Insensitive Reconfigurable Intelligent Surface for Triple Band

This paper presents a 2-bit Reconfigurable Intelligent Surface (RIS) fed by a wideband antipodal Vivaldi antenna (AVA) to achieve high gain and wide angular coverage in three separate bands. The proposed RIS consists of a rectangular array of 20×20 unit cells. Each unit cell has four identical varactor diodes, which facilitate to obtain the desired reflection phase in the three operating bands. The feed antenna has |S11| ≤ -10 dB impedance bandwidth of more than 10 GHz with a peak gain of 9.33 dBi. The RIS possess a peak gains (side lobe level) of 13.6 dBi (22.2 dB), 17.4 dBi (26.3 dB), and 19.2 dBi (31.7 dB) at 3 GHz, 5.2 GHz, and 6.2 GHz, respectively. Moreover, it also shows a beam steering range (with scan loss) of ±25º (1.7 dB), ±45º (4.4 dB), and ±75º (7.1 dB) at 3 GHz, 5.2 GHz, and 6.2 GHz, respectively. The polarization-insensitive unit cells make the proposed RIS usable with x- and y-polarized incident waves.