AbstractIn the microwave wireless power transmission in the solar power satellite system, it is important to obtain design data on the power transmission. Major consideration is given to the effect of microwaves on the electromagnetic environment, such as biological bodies, communication channel, and ionosphere. In this paper, the aperture illumination of the transmitting antenna for the microwave beam transmission is assumed that maximizes the transmission efficiency, and the maximum receivable power. the power density outside the receiving antenna, with consideration given to the electromagnetic environment, is studied. Under the maximum transmission efficiency, the maximum power density outside the receiving antenna is at the edge of the receiving antenna. Hence, the receivable power is obtained when the power density at the center of the receiving antenna and that outside it are restricted below certain values as an environmental constraint. Thus, a design method can be given for a microwave wireless power transmission system. A fast converging numerical method is given for deriving the aperture illumination for maximum transmission efficiency.