Design and Performance Evaluation of a Scalable Rectenna for Microwave Wireless Charging of Modular Lunar Robots

This study presents the design, development, and evaluation of a microwave-based wireless power transmission (MWPT) system to enable efficient, cable-free power delivery to modular robotic systems on the lunar surface. Focusing on MoonBot-an autonomous, reconfigurable robot developed under Japan’s Moonshot R&D program, the research proposes a scalable rectenna system to receive microwave power and wirelessly charge MoonBots deployed for tasks such as lunar exploration and outpost construction. A 2.45 GHz rectenna prototype was developed using a hexagonal patch antenna and a Schottky-diode-based rectifier with 81.7% and 85% RF-DC conversion efficiency at 1 W and 1.3 W input powers respectively. Scaled multi-element configurations were tested to evaluate end-to-end system performance. Far-field simulations were extended to distances up to 1000 m, revealing that a 100 -element rectenna can deliver 100 W of rectified DC power with a transmitted power of 15.17 MW. Furthermore, compact honeycomb layout arrangement of rectenna elements was proposed to enhance power capture and reduce required transmission power. Based on these results, estimated charging times for different MoonBot configurations were calculated. This research demonstrates a scalable and functional MWPT receiver prototype for the potential development of wireless power infrastructure for modular lunar robots.