Recent progress of Wireless Power Transfer via Sub-THz wave

Research on wireless power transmission (WPT) by a rectenna using Sub-THz (herein 100GHz similar to 700GHz) waves is gaining attention. Increasing the frequency, make it possible to improve the beam directivity and to miniaturize rectenna. Therefore, it becomes suitable for long distance and high power WPT. Also, it is expected that energy harvesters at high frequencies will be developed for use with 5 G (28 GHz) and beyond 5G (110 GHz). We succeeded in the world's first sub-terahertz WPT using a gyrotron as a high-power oscillation source. At 303 GHz, a microstrip patch antenna was used for rectenna and record RF-DC conversion efficiency of 2.17 % and rectenna power density (DC output power per unit area) of 3.43 kW/m(2). At 265 GHz, a coplanar slot antenna was used for rectenna and record a RF-DC conversion efficiency of 0.07 % and a rectenna power density of 0.09 kW/m(2). We aim to develope GaN Schottky Barrier Diode (GaN SBD) for high-efficiency WPT in the sub-terahertz band.