关键词: 高空无人飞行平台, 超长航时, 微波传能, 分布式发射, 一体化整流天线, 跟踪导引

Abstract:

High altitude super long endurance UAVs have important application values in the fields of wide view reconnaissance， communication relay， emergency rescue， etc. 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 advantages of long-range transmission and low attenuation of 5.8 GHz microwave. 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. The rectenna adopts a microstrip patch antenna fed by coplanar waveguides. The receiving antenna and rectifier circuit are put on the two 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. The conversion efficiency of microwave to direct current is simulated to 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 the 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 18 km. 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 altitude of 30 m by combining with the extended Kalman filtering algorithm. A 1∶6.7 scaled model is designed to test the developed system. The scaled UAV with rectenna arrays flies through the microwave coverage area generated by a single ground launched antenna with 80 W total power， and the rectenna successfully achieves and transmits the power of the microwave at an altitude of 8 m， which indicates the feasibility of the system proposed.

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