New chip for waking up small wireless devices could extend battery life

A new power saving chip developed by engineers
at the University of California San Diego could significantly reduce or eliminate the
need to replace batteries in Internet of Things (IoT) devices and wearables. The so-called wake-up receiver wakes up a
device only when it needs to communicate and perform its function. It allows the device to stay dormant the rest
of the time and reduce power use. The technology is useful for applications
that do not always need to be transmitting data, like IoT devices that let consumers
instantly order household items they are about to run out of, or wearable health monitors
that take readings a handful of times a day. The problem now is that these devices do not
know exactly when to synchronize with the network, so they periodically wake up to do
this even when there’s nothing to communicate. This ends up costing a lot of power. By adding a wake-up receiver, we could improve
the battery life of small IoT devices from months to years. The wake-up receiver is an ultra-low power
chip that continuously looks out for a specific radio signal, called a wake-up signature,
that tells it when to wake up the main device. It needs only a very small amount of power
to stay on and do this–22.3 nanowatts in this case, about half a millionth the power
it takes to run an LED night light. A key part of this receiver’s design is that
it targets higher frequency radio signals than other wake-up receivers. The signals are in the frequency of 9 gigahertz,
which is in the realm of satellite communication, air traffic control and vehicle speed detection. Targeting a higher frequency allowed researchers
to shrink everything, including the antenna, transformer and other off-chip components
down into a much smaller package–at least 20 times smaller than prior nanowatt-level
work. This wake-up receiver can also do something
else that other nanowatt-powered receivers cannot: perform well over a wide temperature
range. For this receiver, performance is consistent
from -10 C up to 40 C . Typically, performance in low power wake-up receivers drops if the
temperature changes by even just a few degrees. The UC San Diego team developed new circuit
designs and system-level techniques to equip their receiver with all these features while
boosting sensitivity. According to the researchers, this receiver’s
combination of nanowatt-level power consumption, small package size , sensitivity and temperature
performance is the best that has been published to date.

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