An Accurate and Efficient Modelling Approach for Active Reconfigurable Intelligent Surfaces

With the capabilities of beam steering, polarization conversion and information transmission, reconfigurable intelligent surfaces (RIS) are playing a key role in the electromagnetic (EM) world. However, most functional RIS elements need a complex and time-consuming designing process, which greatly limits the development and application of RIS. In this paper, an efficient modelling approach is proposed for the accurate and fast calculation of the reflection coefficients of RIS elements. The key of the method is to separate the active RIS elements into passive structures and tunable devices by using microwave network theory and then calculate their reflected coefficients by matrix operations, thus accelerating the simulation process of the active RIS elements. The accuracy and efficiency of the proposed approach are demonstrated by a 1-Bit phase-modulated active RIS element.