Validating Convex Optimization of Reconfigurable Intelligent Surfaces via Measurements

TL;DR

This paper empirically validates a convex optimization method for RIS design at 3.55GHz, confirming its effectiveness and optimality through real-world measurements and discussing practical implementation aspects.

Contribution

It provides the first practical measurement-based validation of a convex optimization approach for RIS, confirming theoretical predictions and addressing real-world design considerations.

Findings

Empirical confirmation of RIS optimization performance

Validation of reactance value optimality

Discussion of practical RIS measurement techniques

Abstract

Reconfigurable Intelligent Surfaces (RISs) can be designed in various ways. A previously proposed semidefinite relaxation-based optimization method for maximizing power transfer efficiency showed promise, but earlier results were only theoretical. This paper evaluates a small RIS at 3.55GHz, the center of the 5G band "n78", for practical verification of this method. The presented results not only empirically confirm the desired performance of the optimized RIS, but also affirm the optimality of the resulting reactance values. Additionally, this paper discusses several practical aspects of RIS design and measurement, such as the operation of varactor diodes and time gating to omit the direct line-of-sight (LOS) path.