Study on Multipath Retrodirective for Microwave Power Transmission

In this paper, we verified the effectiveness of multipath retrodirective. We calculated and simulated the phase change of the pilot signal caused by the interference with multipath, and both results agreed. Thus, simulating multipath retrodirective, we clarified that the accuracy of multipath retrodirective is determined by the number of elements and the element interval of the Van atta array. Retrodirectivity became better with the number of antenna elements in multipath environment. The transmission efficiency was degraded by mutual coupling when the element interval was $\lambda /4$. When the element interval was $\lambda /2$ and antenna elements were increased, the maximum power was able to transmitted. Comparing maximum power in multipath environment to maximum power in free space, we clarified Multipath Retrodirective is more efficient.