This Fresnel Antenna Is a Ring of Signal-Boosting Wonder Built From Eight Identical PCBs
Designed to provide connectivity to weak Wi-Fi access points, this ring-shaped antenna is really eight relatively simple single-layer PCBs.
Electronics engineer Denys Zaikin, seeking a way to pick up Wi-Fi signals from further afield, has designed an antenna with a difference: it's split into multiple PCBs which can be assembled into a ring, boosting reception based on Fresnel diffraction to a set focal point.
"Initially, the task was to be able to use open Wi-Fi networks that are placed far away and have weak signal levels," Zaikin explains. "The antenna either should have been small or portable or could be assembled/disassembled. The diameter of the antenna should be no more than 70cm for practical use."
Zaikin's initial thought was to build a metal ring, designed to focus signals based on Fresnel diffraction. Simulating various sizes, Zaikin finalized on a ring with a 13.78" external and 9.72" internal diameter — which, while offering around a 9dB gain, isn't terribly portable. The solution: turn it into a jigsaw.
The final design uses eight identical PCBs, corresponding to one-eighth of the overall ring. The design is simple, using only a single metal layer directly on the top of the PCB. Mounting holes provide a means of assembly: segments alternate top-up and top-down so that the metal layers connect, providing an unbroken signal path.
"The presented antenna can theoretically be used as an antenna for Wi-Fi and Bluetooth," Zaikin explains. "[It] seems like antenna gain is close to simulated (9.0dB) and measured as 5…10dB. Around the antenna, there should be some space free of obstacles to avoid shading the rest of the Fresnel zones."
Zaikin's full write-up, along with the PCB design files and simulation details, are available on the project's Hackaday.io page — though the engineer warns that he has yet to test the antenna with a real-world weak Wi-Fi signal in the field.