D-Band Beam Steering on Reconfigurable PB-Phase Metasurfaces

Reconfigurable intelligent surfaces (RIS) are a pivotal technology in addressing terahertz beam tracking and aiming challenges for potential terahertz communication and imaging applications. To overcome the shortcomings of narrow bandwidth and poor reflectance consistency on conventional resonant phase-shift structure, this paper proposes a D-band RIS based on a Pancharatnam-Berry (PB)-phase mechanism. The PB-phase shift is delivered by the surface current reversal controlled by dual GaAs Schottky diodes in mirror placement, giving birth to improved 1-bit coding states with broadband width and consistent reflectance. Simulation results indicate that at a resonant frequency of 140 GHz, the structure achieves a maximum amplitude of approximately −3dB, a −7dB bandwidth spanning about 60 GHz, an accurate 180° phase shift, and a beam scanning range from $\pm 80^{\circ}$ to $\pm 22^{\circ}$. The proposed PB-phase RIS paves a new path to terahertz beam steering and makes it promising for terahertz wireless communication and radar systems applications.