Nisshinbo Micro Devices Inc. and Kenji Itoh Lab, the electrical and electronic engineering department of the Kanazawa Institute of Technology (KIT) College of Engineering, have started the development of radio frequency (RF) rectifier ICs focused on microwave wireless power transfer (WPT) systems.
In recent years, improvements in microwave WPT systems have been studied. It is accelerated due to the publication of the new radio regulation for the microwave WPT in 2022. In microwave WPT systems, an RF rectifier enables long-distance DC power transmission and in reception, it converts the received RF power to DC power for IoT sensors and FA equipment. RF power inputted to rectifiers is dependent on distance from the transmitter. Thus, a high-dynamic range rectifier is required for many kinds of use cases.
According to Nisshinbo’s survey, as rectifier ICs for microwave WPT systems are still unreleased in the current IC market, researchers are studying WPT systems that employ general-purpose diodes in many cases. This makes insufficient rectification efficiencies for microwave WPT systems and poses an obstacle to wider social implementations of microwave WPT systems.
KIT has developed two key technologies: high-efficiency rectification of low power promoted in the program “Scientific Innovation for Energy Harvesting Technology” led by Japan Science and Technology Core Research for Evolutionary Science and Technology; and high-efficiency rectification for 10-watt-class high-power promoted in the program “Energy systems of an Internet of Energy (IoE) Society” led by Cabinet Office Strategic Innovation Program.
Because of such a situation, Nisshinbo and KIT have started the development of RF rectifier ICs focused on microwave WPT systems. The ICs will be mass-produced for the smooth ramp-up of social implementations on microwave WPT systems.
The RF rectifier ICs are configured with gallium arsenide (GaAs) heterojunction field effect transistors (HJFETs). A combination of our unique GaAs wafer processing technology that can construct low-on-voltage and high-breakdown-voltage diodes with KIT’s leading-edge antenna and rectifier circuit technology will realize rectifier ICs that operate more efficiently in low to high-power regions than ever before.
Currently, the following two RF rectifiers are under development:
- 920-MHz-band Rectifier Operatable with Ultra-low Power
- With a combination of the rectifier IC and the antenna designed by KIT, it achieves 21% higher peak efficiency and 5 dB higher sensitivity (which equals to 1.8 times longer transmission distance) than ones with conventional Si SBDs. Also, the breakdown characteristic is increased by 15 dB, which enables the IC to operate in the vicinity of the transmitter.
- 5.7-GHz-band 1 watt rectifier IC
- This 1-watt IC can achieve an efficiency of 20% or more at an input power of 1 mW and achieves a maximum efficiency of 70 to 80% at an input power of up to 1 W.
In the future, Nisshinbo and KIT will research and develop RF rectifier ICs that achieve higher performance and correspond to various frequency bands and power bands in order to contribute to the social implementations of microwave WPT systems.
These research results will be presented and a corporate exhibition is also planned at the 2024 IEEE Wireless Power Technology Conference and EXPO (WPTCE 2024) held in Kyoto University from May 8 through 11, 2024.
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