Wake-up receiver: Electronics in “hibernation”

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Although electronic systems use lots of electricity, they can also help to minimize energy use. With a wake-up chip for example, devices come to life only when there’s something to do.

Refrigerators, coffee machines, toothbrushes, power tools – they can all connect to the Internet. With many of these devices, it’s debatable whether this actually makes sense. The fact is though that the Internet of Things will use large amounts of energy. After all, there will be billions of these connected IoT nodes in the foreseeable future. Although many of them will spend most of the time in stand-by mode when they’re not being used, the sheer number of them will result in alarmingly high global energy consumption. New, innovative concepts are therefore needed.

Scientists from the UC San Diego (University of California San Diego) have come up with one such concept. Their new “frugal” chip is extremely economical when it comes to battery use in IoT devices. After all, the devices are only woken up if they’re actually needed. According to the researchers, this will extend battery life from a few months to a number of years.

Wake-Up Receiver prevents permanent waking up

This method is particularly suitable if data don’t need to be transmitted permanently, for example in measuring stations or portable health monitors. Up until now, these devices woke up regularly, even if there was nothing to communicate.

The Wake-Up Receiver from San Diego looks out for a specific radio signal (waking signature) which then causes an IoT device to start up. It needs just 22.3 nanowatts (nW) to do this.

What makes the receiver different from rival products is its transmission frequency (9 GHz) which is used in satellite communication or air-traffic control for example. This allows the researchers to shrink virtually everything – from the antenna and the transmitter to other off-chip components.

What’s unusual about the receiver is its broad temperature range from -10 to 40 °C. Although this is less important indoors, it’s a must outdoors.

However, the device does have one minor disadvantage: 540 milliseconds elapse between it recognizing the wake-up signal and actually waking up the device. For most applications, this will be inconsequential given the significant increase in battery life.

With its extremely low power consumption (22.3 nW), tiny dimensions (4.55 square centimeters), high sensitivity (-69.5 dBm) and broad temperature range (-10 to 40 °C), the Wake-Up Receiver could be used for a whole host of new IoT applications in the future.

 

The researcher team at the UCSD published its results in an article entitled “A 22.3 nW, 4.55 cm2 Temperature-Robust Wake-Up Receiver Achieving a Sensitivity of -69.5 dBm at 9 GHz” in the IEEE Journal of Solid State Circuits.

 

 

Wake-Up receiver (Image: David Baillot/UCSD).

By only waking up a wireless device when necessary, the wake-up receiver can cut down on power use and extend battery life. (Image: David Baillot/UCSD).