  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.
