Retrodirective antenna array for circularly polarized wireless power transmission

In this paper, a retrodirective antenna (RDA) array for wireless power transmission (WPT) is presented. Applications include the charging of mobile device batteries wirelessly. Thanks to the principle of phase conjugation in mixers, retrodirectivity can be achieved in the far-field. More specifically, the reported RDA architecture deals with an active transmitter module to retrodirect a received beacon tone, with increased power, from a mobile unit and with circularly polarized (CP) radiation. Measurements and simulations show a good agreement in terms of the retrodirective tracking capabilities. In addition, a new RDA architecture is also proposed for WPT, using sub-arrays, in order to boost the overall received power at the mobile while also not significantly increasing the costs of the active transmitter module. Other applications for the proposed RDA circuit element include target tracking, low-cost sensor charging, and other WPT systems.