The concept of producing electrical energy from microwaves could have future implications for low-power sensor networks. Researchers the Japan Science and Technology Agency (JST), Fujitsu Ltd. and the Tokyo Metropolitan University have developed a nanowire backward diode that can convert low-power microwaves into electricity. The technology is expected to play a role in harvesting energy from radio waves in the environment, in which electricity is generated from ambient radio waves.
The researchers succeeded in forming a backward diode that possesses excellent rectification characteristics, even within low voltage ranges in a nanowire that has been miniaturized to a width about one thousandth that of a hair strand. The diode achieved a level of sensitivity more than ten times higher than conventional Schottky barrier diodes, according to the researchers.
One of the research partners, JST, aims to create technologies that convert the unused radiowave energy into electricity to power sensors, information processing devices, and other devices. The use of submicron-sized, minute semiconductor nanowires resulted in a backward diode that combines small size with high sensitivity. Also, by embedding optimized power conversion circuitry into the nanowire backward diode, the researchers will conduct proof-of-principle testing on the power conversion of low-power ambient radio waves.
When researchers tested the new technology at the microwave frequency of 2.4 GHz, the diode exhibited sensitivity of 700 kV/W, roughly 11 times that of the conventional Schottky barrier diode (with a sensitivity of 60 KV/W). Therefore, the technology can efficiently convert 100 nW-class low-power radio waves into electricity, enabling the conversion of microwaves from mobile phone base stations in an area that is over ten times greater than was previously possible. This has led to expectations that it can be used as a power source for sensors.
The researchers plan to further increase the diode’s sensitivity, optimize the diode-integrated antenna, and add power control for voltage consistency, aiming to realize a technology that can generate power anywhere using ambient radio waves.