Study on a Microwave Power Transfer System to a Stratospheric Platform Airship

We investigated a long-range microwave transmission to an airship for a stratospheric platform. In this paper, the feasibility of this system is discussed. Firstly, the optimum size of transmitting antenna and frequency are investigated. 30 m radius antenna is necessary to satisfy the efficiency of 70% at an altitude of 20 km. Considering only the transmission efficiency, 12 GHz is most effective. However, considering the entire system efficiency, 5.8 GHz is suitable. Secondly, we calculate the efficiency for various pointing angles. According to the results, it is desirable that the pointing angle is ± 25 degrees at an altitude of 10 km, and ± 15 degrees at an altitude of 20 km.