Recent wireless power transmission via microwave and millimeter-wave in Japan

From 1980s, Japan has lead a wireless power transmission (WPT) research, especially WPT via microwave or milimeter-wave (MPT) toward a Space Solar Power Satellite (SPS). We have developed high efficiency rectenna at 2.45GHz, 5.8GHz and 24GHz. We have proposed and carried out new beam forming algorism to concentrate a microwave power to targets with phased array technologies. Based on the MPT technologies, we propose not only the future SPS system but also commercial products of the MPT, for example, wireless sensors driven by MPT, EV wireless charging via microwave, and energy harvesting from broadcasting radiowaves, etc. After MIT's innovation of a resonance coupling WPT in 2006, many Japanese start the WPT researches, which are based on bandpass filter theory and technologies. Some commercial products with the WPT appear in Japan. Now we have two consortiums to lead the WPT, which is not only the MPT but also the resonance, inductive, and energy harvesting. One is a Broadband Wireless Forum which focuses on the WPT. The other is Energy Harvesting Consortium which mainly focuses on the energy harvesting. In 2011, Japan conducts the first WPT international conference of “2011 IEEE MTT-S International Microwave Workshop Series on Innovative Wireless Power Transmission: Technologies, Systems, and Applications” in Kyoto, whose chair was the author. On May 10-11, 2012, we have the second IMWS-IWPT again in Kyoto.