A Novel Wideband 1-bit Reconfigurable Intelligent Surface Design for 26 GHz

In this paper, we introduce a novel wideband 1-bit Reconfigurable Intelligent Surface (RIS) design to operate at 26 GHz. The unit-cell, with the compact dimensions of $4.2 \times 4.2 \mathrm{~mm}$, features a hexagon-shaped patch on the top layer and a corresponding full ground plane on the bottom layer. The integration of two pin diodes allows precise control of the unit-cell phase, facilitating operation within the frequency range of 23.8 GHz to 31.1 GHz, with a targeted phase difference of $180^{\circ} \pm 10^{\circ}$ between states. Furthermore, a $10 \times 10$ RIS is design and studied, recurring to CST-MWS full-wave electromagnetic simulation tool. This larger structure maintains the compact design philosophy of the individual unit-cell while achieving noteworthy results. With an aperture efficiency $(\eta)$ surpassing $\mathbf{3 0 \%}$, the $\mathbf{1 0} \times 10$ RIS proves its effectiveness in optimising signal transmission and reception. Moreover, it exhibits a remarkable scanning capability, achieving a scanning angle of ±50° in both