Development of Focused Conical Beam with Null Center for Wireless Power Transfer to Flying Drone

This paper proposes a design method for the focused conical beam with a null center using the Laguerre-Gaussian (LG) mode for wireless power feeding to the drone. For the drone to fly with microwave energy, the rectenna must be attached to the bottom of the aircraft, which causes interference to mission equipment such as cameras. The conical beam with a null in the center avoids this problem. In the case of microwave power transmission, the receiving antenna is in the Fresnel region, so the beam must not only be nulled in the center but also focused toward the receiving antenna. Therefore, in this study, we designed the size of the antenna and its amplitude distribution using the electromagnetic field of the LG-mode. Simulation results with a planar array antenna show that the transmitting antenna of 2.1 m radius can transmit the 24 GHz beam with the air-core ratio of 14% to the receiving antenna of 0.5 m radius located at 40 m above the ground.