Electromagnetics-Based Channel Model of Reconfigurable Intelligent Surfaces

Motivated by recently growing interest in reconfigurable intelligent surfaces (RIS), we introduce a channel model of communication between two arbitrarily positioned end devices assisted by a RIS, where all three devices are characterized using off-the-shelf electromagnetic simulation software. The communication between the devices is assumed to occur via planar electromagnetic waves. This approach correctly represents the electromagnetic coupling between the RIS elements, and also allows the user to choose additional complex weights for path loss between the devices. The user is given a scattering or impedance matrix that exposes all ports of the involved devices, including the RIS element ports, which can be used to optimize the RIS performance for various goals.