Researchers at the Georgia Institute of Technology have uncovered an innovative way to tap into
the over-capacity of 5G networks, turning them into “a wireless power grid” for
powering Internet of Things (IoT) devices that today need batteries to operate.
The Georgia Tech inventors have developed a flexible Rotman lens-based rectifying antenna
(rectenna) system capable, for the first time, of millimeter-wave harvesting in the 28-GHz
band.
(The Rotman lens is key for beamforming networks and is frequently used in radar surveillance
systems to see targets in multiple directions without physically moving the antenna system.)
But to harvest enough power to supply low-power devices at long ranges, large aperture antennas
are required.
The problem with large antennas is they have a narrowing field of view.
This limitation prevents their operation if the antenna is widely dispersed from a 5G
base station.
The researchers have solved the problem of only being able to look from one direction
with a system that has a wide angle of coverage.
The findings were reported in the journal Scientific Reports.
The FCC has authorized 5G to focalize power much more densely compared with previous generations
of cellular networks.
While today’s 5G was built for high-bandwidth communication, the high-frequency network
holds rich opportunity to “harvest” unused power that would otherwise be wasted.
The researchers say that 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.
With the Georgia Tech solution, all the electromagnetic energy collected by the antenna arrays from
one direction is combined and fed into a single rectifier, which maximizes its efficiency.
People have attempted to do energy harvesting at high frequencies like 24 or 35 Gigahertz
before, but such antennas only worked if they had line of sight to the 5G base station;
there was no way to increase their angle of coverage until now.
Operating just like an optical lens, the Rotman lens provides six fields of view simultaneously
in a pattern shaped like a spider.
Tuning the shape of the lens results in a structure with one angle of curvature on the
beam-port side and another on the antenna side.
This enables the structure to map a set of selected radiation directions to an associated
set of beam-ports.
The lens is then used as an intermediate component between the receiving antennas and the rectifiers
for 5G energy harvesting.
This novel approach addresses the tradeoff between rectenna angular coverage and turn-on
sensitivity with a structure that merges unique radio frequency (RF) and direct current (DC)
combination techniques, thereby enabling a system with both high gain and large beamwidth.
In demonstrations, Georgia Tech’s technology achieved a 21-fold increase in harvested power
compared with a referenced counterpart, while maintaining identical angular coverage.
This robust system may open the door for new passive, long-range, mm-wave 5G-powered RFID
for wearable and ubiquitous IoT applications.
The researchers used inhouse additive manufacturing to print the palm-sized mm-wave harvesters
on a multitude 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.
The fact is 5G is going to be everywhere, especially in urban areas.
The researcher says that we can replace millions, or tens of millions, of batteries of wireless
sensors, especially for smart city and smart agricultural applications.
The researcher predicts that power as a service will be the next big application for the telecom
industry, just as data overtook voice services as a major revenue producer.
The research team is most excited by the prospect of service providers embracing this technology
to offer power on demand “over the air,” eliminating the need for batteries.