Super Capacitor and WiFi Speed Optimization for RF Energy Harvesting

This paper proposes an innovative RF harvesting circuit allowing a BLE data transmission of a connected object, every two hours, and being powered by WiFi router signal. The circuit relies on a rectifier, which converts the received RF power into a DC signal to power the connected object. The harvesting system needs an intermediate energy storage element between the rectifier and a voltage boost, like a super capacitor, to store the converted energy. The influence of two parameters has been studied to test for the feasibility of a such system. First, the choice of the super capacitor configuration will greatly influence the system efficiency, due to the capacitor's intrinsic losses. Second, the WiFi connection speed will influence on the transmitted RF power. It appears that the maximal datarate (25 Mbits.s-1) of the used router allows to transmit the maximal RF power which will be received and converted by the proposed system. A succeeded transmission has been performed by placing our harvesting system at a distance of 25 cm from the router.