Design of a transparent reconfigurable intelligent surface with photosensitive silicon

• Main Author: Lu, Mingyan
• Other Authors: Shen Zhongxiang
• Format: Thesis-Master by Coursework
• Language: English
• Published: Nanyang Technological University 2023
• Subjects: Engineering::Electrical and electronic engineering
• Online Access: https://hdl.handle.net/10356/171955
• Institution: Nanyang Technological University

This dissertation presents the design and evaluation of a transparent reconfigurable intelligent surface (RIS) controlled by photosensitive silicon. The RIS unit cell is initially designed with a split-ring resonator (SRR) structure using photosensitive silicon, enabling precise control of reflection and transmission amplitudes. However, this design exhibits limited phase tuning capabilities. To overcome this limitation, an improved RIS cell design is proposed by replacing the SRR structure with square silicon rings. This modification enhances the phase adjustment range of the RIS unit, enabling a wider range of phase variations. Experimental results demonstrate that the improved RIS unit, under the irradiation of a 500mW pump light source at a frequency of 28GHz, achieves a reflection amplitude exceeding 90% and a 360-degree adjustable phase. Based on the enhanced RIS unit, two beamforming methods are introduced. The first method utilizes the distance between substrates to design the beamforming deflection angle, while the second method considers the angle of the lower substrate. These methods exploit the improved phase adjustment capabilities of the RIS unit. The effectiveness of the proposed methods is validated through the construction of 12x12 and 9x9 RIS array models, achieving accurate beamforming at the desired angles. The aperture efficiencies of the implemented methods are measured to be 83.40% and 95.17%, respectively.