Design of 2.45 GHz microwave wireless power transfer system for battery charging applications

A compact 2.45 GHz receiver module for wireless charging at far distance has been developed. The module consists of receiving antenna array, rectifier and power management circuit. The design, fabrication and testing of the receiving antenna, rectifier and power management circuits will be described. By integrating the 3 by 4 rectenna array and the power management circuit, the total weight of the complete module is around 500 g, making it feasible to mount on any system with rechargeable battery. Its functionality to receive and convert the microwave power to DC power for charging an unmanned aerial vehicle (UAV) battery is demonstrated. Using the developed system and through careful experimental study, the feasibility of charging a UAV battery at varying distance of 1 to 4 m is studied. It is demonstrated that at a test distance of 2m, the UAV battery can be turned on and its power charging mode is activated, under the illumination of microwave through a horn transmitting antenna when its transmitting power is about 130W. By increasing the distance to 4m, the UAV battery can be turned on and power charging mode is activated the transmitting power reaches about 170W. At a closer distance of 1m, the maximum charging current of 190mA is achievable when the transmitting power is 500W, which is the maximum output power limit of the power amplifier. According to the test results of the receiver module and theoretical calculation, it can be estimated that a transmitting power of 12kW is needed to charge the UAV's battery under the flying mode at the distance of 4 m.