Measurement and characterization of a reconfigurable intelligent surface with an automated measurement environment

Abstract

A reconfigurable intelligent surface (RIS) is an important novel technology of the sixth generation of mobile communications (6G). It promises to extend the coverage area of a base station to previously shadowed areas through anomalous reflections. It comprises an array of RIS elements, which can adjust their reflection coefficients. This thesis uses a square RIS with $6\times6$ elements based on varactor diode technology. Reflecting an incident wave towards a specific direction is accomplished with a clever arrangement of its reflection coefficients, referred to as beam-focusing or beam-forming. To achieve this, knowledge of the reflection coefficients of the individual RIS elements is necessary. This thesis aims to determine these reflection coefficients based on a series of measurements performed using an automated measurement environment. The results of these measurements enable the evaluation of the performance of the RIS in terms of its magnitude and range of available phase shifts. These results are then compared to prominent RIS channel models, highlighting their differences. The data that has been acquired can be used for further research into RIS channel models and beam-focusing algorithms.