Beyond-Diagonal RIS Prototype and Performance Evaluation

TL;DR

This paper introduces the first experimental prototype of a beyond-diagonal reconfigurable intelligent surface with reconfigurable inter-element connections, demonstrating performance benefits and hardware constraints through extensive evaluations.

Contribution

It presents the first prototype of a BD-RIS with reconfigurable inter-element connections and analyzes the impact of hardware constraints on performance.

Findings

Inter-element connections improve performance in rich-scattering environments.

Hardware constraints significantly affect the achievable performance.

Mutual-coupling awareness is crucial during optimization.

Abstract

We present the first experimental prototype of a reflective beyond-diagonal reconfigurable intelligent surface (BD-RIS), i.e., a RIS with reconfigurable inter-element connections. Our BD-RIS consists of an antenna array whose ports are terminated by a tunable load network. The latter can terminate each antenna port with three distinct individual loads or connect it to an adjacent antenna port. Extensive performance evaluations in a rich-scattering environment validate that inter-element connections are beneficial. Moreover, we observe that our tunable load network's mentioned hardware constraints significantly influence, first, the achievable performance, second, the benefits of having inter-element connections, and, third, the importance of mutual-coupling awareness during optimization.