Abstract: High altitude super long endurance UAVs have important application values in a field of wide view reconnaissance, communication relay, emergency rescue and other fields. In order to achieve true super long endurance flight, a high-altitude unmanned flight system based on ground distributed launched microwave energy devices is proposed by utilizing the performances of 5.8GHz microwave with long-range transmission and low attenuation. The flight system mainly includes the flight part (rectenna), distributed transmission part, and high-precision guidance and tracking system for the interconnection of heaven and earth. Among which, the rectenna adopts a microstrip patch antenna fed by coplanar waveguides. The receiving antenna and rectifier circuit are designed on both sides of a layer of dielectric substrate. The rectifier circuit is optimized based on a direct through filter of a coplanar wave-guide, forming a circularly polarized rectifier array, and the conversion efficiency of microwave to direct current is simulated to be exceed 50%. The rectenna is fused with the body of the UAV in an approximate composite sandwich structure, forming a replaceable circular antenna area in the flat area of the lower part of the body. An after-loaded airfoil with a flat lower surface is used in this wingbody-rectenna region, and an optimized high-lift airfoil is applied in outer sections of the UAV to ensure the overall efficiency of the UAV. The microwave launched antenna adopts a distributed transmitting array that is divided into several single parts and driven by servo systems to track the flight platform, and composites a microwave coverage area at the altitude of 18km. The simulation data show that the beam collection efficiency of the launched system can reach up to 80%. The tracking guidance system also uses the distributed locating strategy, which can achieve ultra-high precision location of the UAV with an error of 30m combining extended Kalman filtering algorithm at high altitude. A 1:6.7 scaled model has been designed to test the designed system. The scaled UAV with the rectenna arrays fly through the microwave coverage area generated by a single ground launched antenna with 80W total power, and the rectenna successfully achieves and transmits the power of the microwave at a altitude of 8m, which indicates the feasibility of the system.

Key words: high altitude UAV, super long endurance, microwave energy transmission, distributed launch, integrated rectenna, track and guide