December 2021, ScientificAmerican.com 55COMPUTINGENERGY FROM
WIRELESS SIGNALS
5G will help power
the Internet of Things
By Joseph Costantine
The wireless devices that make up the Internet of
Things (IoT) constitute the backbone of an ever more
networked world. They are deployed as gadgets in
homes, as wearable devices for biomedical uses, and
as sensors in hazardous and hard-to-reach areas. As
the IoT grows, it is enabling agricultural practices that
use less water and pesticide; more energy-efficient
smart grids; sensors that monitor flaws that can weaken
bridges or concrete infrastructure; and early-warning
sensors for disasters such as mudslides and earthquakes.
With an estimated 40 billion IoT devices coming
online by 2025, providing convenient, on-demand
power to those devices is a fast-growing challenge.
One solution that is already in the works leverages the
wireless signals emanating from Wi-Fi routers and
access points. The emerging fifth generation of cellular
technology, or 5G, will elevate wireless-energy har
vesting to a new level.
With 5G, the Federal Communications Commis
sion is allowing cell signals to move into the higher (but
still safe for humans) millimeter range of the electro
magnetic spectrum for the first time. Along with
higher information rates, 5G wireless signals transmit
a greater amount of radiated energy than 4G. This
capability points to a future where many low-power
wireless devices never need to plug in to charge.
How can devices grab power from wireless signals?
Wi-Fi and 5G are electromagnetic waves that propa
gate at frequencies within the broad spectrum be -
tween FM radio, microwaves and millimeter waves.
The first step of the process involves a receiving
antenna that captures energy carried with the wireless
signal. The antenna routes that energy into an elec
tronic rectifier circuit, which in turn uses semiconduc
tors to convert it into a direct-current (DC) voltage
that can charge or power a device. This combination
of antenna and rectifier (or converter) is called a rec
tenna. A power-management circuit follows the rec
tenna, amplifying the voltage while itself consuming
negligible power.
Many start-up companies are now offering wireless
charging products that currently rely on dedicated
wireless transmitters; research suggests it is likely,
however, that such devices will be able to harvest
Wi-Fi and 5G signals in the near future. Just as cell
phones free us from landlines and have transformed
our communication ability, this emerging technology
will free us even further.EMERGING TECHNOLOGIES 2021