Multiport Network Theory for Modeling and Optimizing Reconfigurable Metasurfaces

TL;DR

This work surveys the use of multiport network theory ($MNT$) to model and optimize reconfigurable intelligent surfaces (RIS) in wireless networks, emphasizing electromagnetically consistent representations via impedance ($Z$-parameters) and scattering ($S$-parameters) formalisms. It documents a spectrum of modeling approaches, from diagonal and non-diagonal impedance and scattering matrices to physics-compliant representations like Chu theory, Floquet modes, and coupled-dipole formalisms, and discusses optimization strategies including Neumann-series-based methods and alternatives. Validation is provided through full-wave simulations and experimental measurements, highlighting the ability of MNT to capture mutual coupling, structural scattering, and rich scattering environments, with efficient PEEC-based simulators enabling design loops. The review identifies the key practical insights, such as the benefit of non-diagonal representations to handle coupling and the need for a manageable number of RIS parameters, and it outlines future directions toward physics-based, simulation-free models for integrated sensing and computing in the wave domain.

Abstract

Multiport network theory (MNT) is a powerful analytical tool for modeling and optimizing complex systems based on circuit models. We present an overview of current research on the application of MNT to the development of electromagnetically consistent models for programmable metasurfaces, with focus on reconfigurable intelligent surfaces for wireless communications.