A new, energy-efficient chip has been developed in the laboratories at the University of California San Diego which could significantly extend battery life in IoT sensor applications and mobile devices. A device using the wake-up receiver will only be activated when the receiver detects a specific signal (the wake-up signature) otherwise only the receiver section remains listening, consuming very little energy.
 
The technology is particularly suitable for applications that transfer data sporadically, such as IoT sensors monitoring non-critical signals or portable health monitors which only take measurements a few times a day. It’s often the case that devices in a network will waste energy by routinely powering up and synchronizing with the network even when there is no new data to send. Researchers were able to boost battery life from months to years for small IoT devices using the wake-up chip to switch the device.
 
Close up of the chip stack. Image: David Baillot / UCSD.

The wake-up chip

The UCSD research team published their findings under the title "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. The receiver is an extremely energy-efficient chip (using just 22.3nW) to continuously look for a particular radio signal (the wake-up signature) to activate the main unit.

The wake-up signals operate at 9 GHz, within the microwave X band, which is also used for satellite communications, radar and wireless communications networks. The benefit of using such a short wavelength is that the antenna and associated components can all be contained in a relatively small package. The unit was specifically designed to operate over a wide (-10 to 40 ° C) temperature range to ensure its suitability for use in equipment designed for indoor and outdoor use.