Open Source Reconfigurable Intelligent Surface for the Frequency Range of 5 GHz WiFi
Markus Heinrichs, Aydin Sezgin, Rainer Kronberger
TL;DR
This work tackles the barrier to RIS experimentation by delivering an open-source, low-cost RIS design for the $5$ GHz WiFi band ($5.15$-$5.875$ GHz) on FR4, enabling broader replication and real measurement studies. The authors present a rectangular patch unit cell with a via and a binary SPDT switch that achieves a near-$180^ op$ phase shift, optimized via CST with a compact TL$_1$ and a $w=0.42$ mm, $l=9.1$ mm geometry, and integrate a $16 imes16$ RIS with a backside controller for USB or BLE operation. RF measurements validate the surface performance, showing a minimum reflection of $-5.2$ dB at $5.56$ GHz (OFF) and $-4.8$ dB at $5.15$ GHz (ON), with phase differences peaking at $180^ op$ around $5.53$ GHz and falling to $92^ op$ at $5.875$ GHz, all benchmarked against a metal reference. The contributions include open fabrication data and firmware, facilitating accessible, repeatable measurements and practical deployment; this enables researchers to perform RIS experiments without prohibitive cost or custom fabrication time, accelerating progress in wireless sensing and communications.
Abstract
Reconfigurable Intelligent Surfaces (RIS) have been identified as a potential ingredient to enhance the performance of contemporary wireless communication and sensing systems. Yet, most of the existing devices are either costly or not available for reproduction. To close this gap, a Reconfigurable Intelligent Surface for the frequency range of 5 GHz WiFi is presented in this work. We describe the designed unit cell, which is optimized for the full frequency range of 5.15 to 5.875 GHz. Standard FR4 substrate is used for cost optimization. The measured reflection coefficient of a rectangular RIS prototype with 256 elements is used for RF performance evaluation. Fabrication data and firmware source code are made open source, which makes RIS more available in real measurement setups.