Metasurface-Based Antenna Turns Ambient Radio Waves Into Electric Power

The technology could make it possible to use radio emissions from cellular networks to wirelessly power sensors and LEDs.

Researchers have developed a new metasurface-based antenna, which represents an important step towards practical use of energy harvested from radio waves, such as those used in cellular networks or Bluetooth connections. This technology could potentially wirelessly power sensors, LEDs, and other simple, low-power devices.

“By eliminating cable connections and batteries, these antennas could help reduce costs, improve reliability and make some electrical systems more efficient,” said research team leader Jiangfeng Zhou of the University of South Florida. “This would be useful for powering smart home sensors, e.g. such as those used for temperature, lighting and movement, or sensors used to monitor the structure of buildings or bridges where replacing a battery might be difficult or impossible.”

In the diary Express for optical materials, the researchers report that laboratory tests of their new antenna have shown that it can harvest 100 microwatts of power from low-power radio waves, enough to power simple devices. This was possible because the metamaterial used to make the antenna has perfect absorption of radio waves and is designed to work at low intensities.

The researchers tested their metamaterial-based antenna in an anechoic chamber. The radio wave is emitted by the horn antenna on the left and received by the meta-surface antenna mounted on the wooden frame on the right. The anechoic chamber eliminates background signals from other sources and prevents stray signals from the radio wave source from bouncing around the room and interfering with measurements. The image of the metamaterial-based antenna is zoomed in on the right. Credit: Jiangfeng Zhou and Clayton Fowler

“Although more work is required to miniaturize the antenna, our device exceeds a key threshold of 100 microwatts of harvested power with high efficiency using ambient power levels found in the real world,” said Clayton Fowler, the team member who developed the Sample prepared and performed the measurements. “The technology could also be adapted so that a radio wave source could be provided to power or charge devices in a room.”

Get energy from the air

Scientists have been trying to harvest energy from radio waves for a long time, but harvesting enough energy to be useful has been difficult. This is changing thanks to the evolution of metamaterials and the ever-increasing number of available environmental sources of radiofrequency energy, such as cellular networks, Wi-Fi, GPS, and Bluetooth signals.

“With the tremendous explosion of radio wave-based technologies, there will be a lot of electromagnetic waste emissions that could be collected,” Zhou said. “Combined with advances in metamaterials, this has created a mature environment for new devices and applications that could benefit from the collection and utilization of this waste energy.”

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