Mathematical Model and Real-World Demonstration of Multi-Beam and Wide-Beam Reconfigurable Intelligent Surface

• Published in: IEEE access Vol. 11; pp. 19613 - 19621
• Main Authors: Bagheri, Amirmasood, Safaei, Mahmood, Araghi, Ali, Shahabi, S. M. Mahdi, Wang, Fan, Khalily, Mohsen, Tafazolli, Rahim
• Format: Journal Article
• Language: English
• Published: Piscataway IEEE 2023; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: 6G mobile communication; Angle of reflection; Array signal processing; Attitude (inclination); beam forming; Cost function; genetic algorithm (GA); Genetic algorithms; Mathematical analysis; mathematical modeling; Mathematical models; Optimization; Phase distribution; Reconfigurable intelligent surface (RIS); Reconfigurable intelligent surfaces; Reflection; Surface waves; test-bed; Voltage
• ISSN: 2169-3536; 2169-3536
• DOI: 10.1109/ACCESS.2023.3248501

In this paper, a mathematical model is proposed to govern the phase distribution on a reconfigurable intelligent surface (RIS) for anomalously reflecting the beam towards the directions of interest. To this end, two operational modes are defined with respect to the reflected pattern. In the first mode, the RIS is configured to form multi-reflected beams toward the directions of interest capable of being controlled independently. The second mode is when the RIS provides a wide reflected beam. Regarding to each mode, a cost function is derived and then, in order to enhance the reflected pattern characteristics, a genetic algorithm (GA) is employed to the model as optimization method. To validate the practicality of the method, the proposed model is applied to a fabricated RIS to assess its performance in a real-world outdoor scenario. In the first mode, an asymmetric dual-beam reflected pattern is obtained and tested with tilt angles of <inline-formula> <tex-math notation="LaTeX">\theta _{0}=60^{\circ } </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">\theta _{1}=135^{\circ } </tex-math></inline-formula>. Furthermore, a wide-reflected beam is generated in the second mode with half-power beamwidth of <inline-formula> <tex-math notation="LaTeX">\theta _{HPBW}=30^{\circ } </tex-math></inline-formula> and tilt angle of <inline-formula> <tex-math notation="LaTeX">\theta _{0}=75^{\circ } </tex-math></inline-formula>. At both modes, the measured data are well aligned with the simulated results.