The dense focus of 5G creates a significant amount of power, much of which goes unused, so the project created an antenna system that can harvest it. In essence, the Georgia Tech discovery helps funnel 5G waves to devices, so they don’t have to rely on batteries, said Aline Eid, senior researcher in the Athena lab, which studies technologies for electromagnetic, wireless, and other applications. In the future, electricity providers could even offer power on demand “over the air,” Tentzeris said. “5G is going to be everywhere, especially in urban areas,” he added.
Because 5G networks are specifically built for high-bandwidth connection, the U.S. Federal Communications Commission (FCC) has authorized them to focus power much more densely than 4G networks. That means the high-frequency network will have a great deal of unused power that—unless “harvested”—will be wasted, he said.
That harvested energy could fuel the many battery-powered devices around us, like the sensors that help make up the IoT and that monitor conditions in homes, cities, autonomous cars, and even—via wearable electronics—inside our bodies.
“There’s been a lot of discussion of biomonitoring,” Tentzeris said. “In a wearable configuration, for monitoring glucose or blood pressure or sleep, you could have systems literally working for years and without the need for a battery charge.” The energy could be used for sensors in rugged environments where batteries aren’t an option, he added.
Power-as-a-service may well be a way for the telecom industry to supply electricity in the same way that many software makers today provide access to their applications in the cloud rather than through downloadable software, he added. Doing away with batteries will be a boon to the environment, Eid said.
“By 2025 you’ll be surrounded by billions of devices. That is the promise of IoT,” she said. “Billions of devices means billions of batteries being continuously replaced and continuously discarded at a huge cost to our environment, while there is power all around us.”
In order for a world without batteries to come to pass, researchers needed to find a way to tap into the 5G network. The Georgia Tech researchers believe they’ve found a way to do that.
Like its predecessors, the 5G networks service areas are divided into small geographical areas called cells. An antenna in each cell sends out radio waves that connect all the 5G wireless devices in that cell to the internet and to cellphones.
“People have attempted to do energy harvesting at high frequencies like 24 or 35 gigahertz before,” Eid said. But the antennas used only worked if they had line of sight to the base station.
Now, she and her colleagues developed a small, flexible Rotman-lens-based rectifying antenna (rectenna) system, capable, for the first time, of millimeter-wave harvesting in the 28-GHz band.
But to harvest enough power to supply low-power devices at long ranges requires antennas with large apertures. The problem with the larger antennas required to harvest 5G power is they have a narrowing field of view, which hinders operation from a 5G base station. In other words, the larger antennas cannot get a line of sight onto the 5G base stations, which exist in many more locations than those for 28G bands.
The Georgia Tech researchers created a system with a wide angle of coverage, which solves the problem of only being able to look from one direction, said Jimmy Hester, senior lab advisor.
“With this innovation, we can have a large antenna, which works at higher frequencies and can receive power from any direction. It’s direction-agnostic, which makes it a lot more practical,” he said.
The key to seeing in many directions is the researchers’ optical lens as an intermediate component between the receiving antennas and the rectifiers.
Operating just like an optical lens, their Rotman lens can see six fields of view at the same time. The Rotman lens is key for beam-forming networks and is frequently used in radar surveillance systems to see targets in multiple directions without physically moving the antenna system, Tentzeris said.
For their 5G device, they’ve devised a way to print the antennas and to tune the shape of the lens, which results in a structure with one angle of curvature on the beam-port side and another on the antenna side. This enables the antenna to map a set of selected radiation directions to an associated set of beam-ports; to “see” in six directions, he added.
Prototype of mm-Wave Energy Harvester. Image Credit: Georgia Tech
Incorporating 3-D printing into their technology, the researchers printed the palm-sized wave harvesters on many types of everyday flexible and rigid substrates. Providing 3D and inkjet printing options will make the system more affordable and accessible to a broad range of users, platforms, frequencies, and applications, Hester said.
For instance, the harvester on a wearable device would ensure it has the energy to keep counting your steps. In demonstrations, Georgia Tech’s technology achieved a 21-fold increase in harvested power compared with another harvesting device, Eid said.
“With this innovation, we can have a large antenna, which works at higher frequencies and can receive power from any direction. It’s direction-agnostic, which makes it a lot more practical,” noted Jimmy Hester, senior lab advisor and the CTO and co-founder of Atheraxon, a Georgia Tech spinoff developing 5G radio-frequency identification (RFID) technology.
“I’ve been working on energy harvesting conventionally for at least six years, and for most of this time it didn’t seem like there was a key to make energy harvesting work in the real world, because of FCC limits on power emission and focalization,” Hester said. “With the advent of 5G networks, this could actually work and we’ve demonstrated it. That’s extremely exciting — we could get rid of batteries.”
This work was supported by the Air Force Research Laboratory and the National Science Foundation (NSF) – Emerging Frontiers in Research and Innovation program. The work was performed in part at the Georgia Tech Institute for Electronics and Nanotechnology, a member of the National Nanotechnology Coordinated Infrastructure (NNCI), which is supported by the NSF (Grant ECCS-1542174).
A. Eid, et al., “5G as a wireless power grid.” (Scientific Reports, 2021) https://doi.org/10.1038/s41598-020-79500-x