Dr. Maho Matsukura

Program Assistant Professor

The University of Tokyo

My research centers on high-power microwave wireless power transmission (WPT), complemented
by work in plasma/propulsion background. I investigate the frequency dependence of RF-DC
conversion efficiency to derive design rules for kilowatt-class tube type receivers from microwave to
millimeter-wave bands. On the semiconductor side, I designed and tested rectennas (that represent
antenna and rectifier circuit), quantified safe operating envelopes under non-uniform distribution using
gyrotron, and demonstrated sub-millisecond response that resolved beam transients and spatial
structure. These studies inform frequency-aware rectenna design, beam shaping, and receiver
protection in high power density operation.
Building on insights from semiconductor circuit tests, I focused on design knowledge for the
Cyclotron Wave Converter (CWC) as a candidate high-power rectifier for WPT in electrified
aerospace. The CWC is a vacuum device that rectifies microwave by accelerating electrons through
interaction between an electric field in a cavity and an electron-gun beam. I first examined the simplest
cavity geometry and quantified how RF-DC conversion efficiency varies with frequency. To analyze
electron trajectories and accelerations, I developed a particle-in-cell simulation code derived from
Hall-thruster modeling framework. The model coupled electron movement calculations with the
spatial electric-field distribution of the designed cavity, enabling rapid scans from microwave to
millimeter-wave bands. Using this code, I mapped efficiency–frequency operating characteristics and
identified design trade-offs that guide cavity tuning and beam parameters. Going forward I will (i)
design and fabricate higher-efficiency, manufacturable CWC prototypes, (ii) develop a WPT system
for high power-density, and (iii) explore integration with electric-propulsion subsystems.