Wireless far-field charging of a micro-UAV

Flight time of micro-UAVs is limited by the battery size they can carry. Typically, they need to land and recharged after about 10 minutes. This paper presents a method for wirelessly charging the UAV battery when it lands, without the need to remove it and replace it. The system consists of a light-weight flexible rectenna array mounted on the UAV body and micro-controller driven power management circuit that enables efficient battery charging. In this work, a frequency of 5.9GHz is chosen as a compromise between size and rectifier efficiency. The UAV battery is charged from the edge of the far field with about 5W of transmit power.