This paper describes the design, fabrication, and testing of a Reconfigurable Intelligent Surface (RIS) operating within the millimetre wave (mmWave) spectrum for 5G communication. Numerical simulations detail the operation of a 1-bit unit cell controlled by a p-i-n diode and biased with RF chokes within the n257- 5G FR2 band (26.5−29.5 GHz) at the optimized angle of incidence of ±30◦. For designing the RIS, a theoretical model was evaluated to calculate the free-space path loss of an RISassisted wireless link, helping to select the most cost-effective RIS aperture area. The RIS design is based on a planar dipole reflector, interlaced to form a checkerboard lattice, supporting dualpolarization operation. A multi-layer RF and electronics printed circuit board (PCB) is fabricated to evaluate design performance at both the unit cell and finite RIS array levels. Experiments are conducted to verify that the RIS performance aligns with analytical and simulated results. Finally, the RIS is tested in real-world scenarios, demonstrating its capabilities in reflected signal strength. Practical RIS performance makes it a promising candidate for reliable mmWave wireless communication systems.
Machado et al. (Sun,) studied this question.