Millimeter-Wave Retrodirective Wireless Power Transfer Applicable to Small Electronic Devices

With the recent surge in popularity of the Internet of Things (IoT), there also has been a notable increase in research on wirelessly charging IoT enabled electronic devices. Millimeter-wave retrodirective power beaming has recently emerged as a suitable candidate for wirelessly charging small electronic devices. In this paper, we propose and demonstrate a millimeter-wave power beaming concept applicable to IoT ecosystem. The proposed system incorporates a Rotman lens retrodirective beamformer as a Tx unit. To demonstrate the retrodirective power beaming, a Rotman lens beamformer on a waveguide platform is designed to operate at Ka-band. The proposed Rotman lens operates with seven beam ports capable of radiating seven beams within $\pm$30° steering range. On the receiving end, a rectenna consisting of a patch array and rectifier is designed. We then conducted an end-to-end power beaming experiment as proof of concept, where the results demonstrate the capability of the proposed system as a retrodirective millimeter-wave power beaming system.