Research Activities at RISH on Antennas For Microwave Power Transmission
Prof. Daotong Li (Chongqing University, Chongqing, China)

His principal activity mainly focuses on the antennas for microwave power transmission, and some research works on the antennas and arrays with high gain, near-field focusing, pattern and beamwidth reconfigurable characteristics and the further application in MWPT are carried out. As we all know that Microwave wireless power transmission (MWPT) technology, which plays an important role in Space Solar Power Systems (SSPS) and IoT applications, can convert electrical power into microwave power and wirelessly transmit it into free space through a transmitting antenna, and it is captured by the rectenna and converted into DC power. As one of the most important parts of MWPT, the antenna is the interface between the EM waves propagating in space and the transmitter and receiver. Thus, the antennas with high gain, high efficiency, beam scanning and compact size are highly desired.

During his stay at RISH, Kyoto University, he has worked on the following research topics. Some theoretical analysis on the current MWPT technology and the theoretical and technical limitations for improving the efficiency are carried out, and the corresponding solutions of antenna element and array such as antenna unit characteristics, antenna array beam forming technology, beam pointing control technology, for high efficiency MWPT are proposed and investigated. The antenna with higher gain can improve the efficiency of the MWPT system, the high-order resonant mode dielectric resonator antenna and array are proposed to improve the gain, and the radiation pattern reconfigurable antenna is further developed to realize the multi-beam and dynamic MWPT. Furthermore, other antenna gain enhancement technology research has also been carried out, such as lens antenna, high gain Yagi-Uda antenna. For the transmitting antenna subsystem, in order to improve the system integration and miniaturization, some researches on the high-performance multifunctional antenna are implemented, for example, filtering Lens antenna, filtering high gain quasi-Yagi antenna. Moreover, the reconfigurable reflectarray for near-field focusing and far-field WPT is also analyzed and implemented. The high-performance rectenna, as the receiving antenna subsystem, is also one of the most important parts to improve the efficiency of the whole MWPT system. A high efficiency rectenna with angle insensitivity and polarization insensitivity is proposed and implemented to solve the problem of efficiency degradation caused by incident angle and polarization sensitivity.

Finally, I would like to express my sincerest thanks to my host Prof. Naoki Shinohara for his time, interest, and very warm hospitality during my stay. I hope and expect that our collaboration will continue and expand in the future. I am also thankful to Prof. Bo Yang for the discussions on MWPT technology. Thanks to Ms. Mami Furukoshi for helping me in all administration and guest house matters.

Figure Antennas for microwave wireless power transmission