Wideband Sub-THz Reconfigurable Intelligent Surface Using Planar Tightly Coupled Dipoles

In this letter, we present a proof-of-concept study of a 1-bit wideband reconfigurable intelligent surface (RIS) using planar tightly coupled dipoles (PTCDs). The PTCD RIS has a planar configuration with a single dielectric layer bonded to a ground plane and is fabricated using cost-effective printed circuit board (PCB) technology. Each RIS unit element achieves binary phase shifting by altering the polarization of the reflected wave by 180$^\circ$. Cosimulation of the switch model with the RIS unit cell verifies the performance of the RIS. Passive prototypes are fabricated to demonstrate the concept, achieving a 3 dB gain bandwidth of 27.4% at the center frequency of 102 GHz, validated through simulations and measurements. Analytical calculations of the RIS response show good agreement with the simulated results.