Theoretical and experimental studies of retro-reflective antenna array for microwave power transmission from space solar power satellite to earth

The development of space solar power satellites aims to harvest solar power by artificial satellites over the earth’s geostationary orbit and then deliver the harvested power to the earth wirelessly. The retro-reflective antenna array technique is believed to be a close-to-optimal technical approach to achieve efficient wireless power transmission from a geostationary satellite to the earth, as it is capable of generating a microwave power beam aiming at a ground station on the earth via analyzing a pilot signal broadcasted by the ground station. In this paper, some of our preliminary research outcomes on retro-reflective antenna array for space solar power applications are reported. In the theoretical part of this paper, closed-form formulations with precision better than the classic theory of phased array are derived to analyze the performance of retro-reflective antenna array when the far zone condition is not satisfied between the space solar power satellite and the ground station. In the experimental part of this paper, a bench-scale retro-reflective antenna array with physical dimensions of about 0.6 m by 0.6 m is fabricated and tested. The theoretical and experimental results demonstrate that the microwave beam generated by a satellite-borne retro-reflective antenna array could be adjusted in real time to aim at the location from which the pilot signal stems. Based on the theoretical and experimental studies of this paper, systematic research endeavors are being conducted on the retro-reflective antenna array for space solar power applications.