5G – a future wireless energy supply


A solution has been proposed to harvest energy from the 5G network to power Internet of Things (IoT) devices and wearables.

Wireless charging is becoming increasingly common for smart phones, devices such as toothbrushes and razors and even electric vehicles. So far, however, the practical range is limited, which in turn limits its uses.

But that could be set to change with the new solution from researchers at Georgia Institute of Technology in Atlanta, GA, opening the prospect for wireless charging in the future to become as ubiquitous as Wi-fi is today.

The solution from Georgia Tech incorporates a special lens system known as a Rotman lens into an antenna, in order to enable energy to be harvested across a wide angle of coverage in the 5G 28GHz frequency band.

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The challenge to harvest enough power to supply low power devices at long ranges is that large aperture antennas are required. However, large antennas have a narrowing field of view, which limits their operation if they are widely dispersed from a 5G base station.

The Rotman lens, which operates like an optical lens, is key for beamforming networks and is frequently used in radar surveillance systems to see targets in multiple directions without the need to move the antenna system.

“We’ve solved the problem of only being able to look from one direction with a system that has a wide angle of coverage,” said senior researcher Aline Eid in Georgia Tech’s ATHENA lab and lead author of the report in the journal Nature.

“People have attempted to do energy harvesting at high frequencies like 24 or 35GHz 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.”

The Georgia Tech’s palm sized 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.

Further, in 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 maximises its efficiency.

The technology is claimed in demonstrations to have achieved a 21-fold increase in harvested power compared with a referenced counterpart, while maintaining identical angular coverage.

In its current configuration it offers a harvesting ability up to a distance of 2.83m and exceeding 180m using state-of-the-art rectifiers (estimated around 6μW at 180m).

Energy as a service

As a further drive to lower the costs, the researchers used in-house additive manufacturing to print the 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 research team envisages that with the expected widespread availability of 5G, millions of batteries in wireless sensors in use cases such as smart cities could be replaced with the technology.

In addition, besides supporting an energy efficient approach to 5G implementation, ‘power as a service’ could become a new big application for the telecoms industry.

“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 limits on power emission and focalisation,” said Jimmy Hester, senior lab advisor in Georgia Tech’s School of Electrical and Computer Engineering.

“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.”