Researchers at Stanford University have concocted a way of extending smartphone and tablet battery life.
Referring to how a sleeping device can still suck the life out of a battery, the researchers have developed a "wake-up receiver" that can "turn on a shut-off device at a moment's notice".
Graduate student, Angad Rekhi, has been working in the Arbabian lab at Stanford, alongside assistant professor of electrical engineering, Amin Arbabian, who together developed the wake-up receiver, which turns on a device in response to incoming ultrasonic signals.
According to the researchers, these signals are outside the range that humans can hear, and by working at a significantly smaller wavelength and switching from radio waves to ultrasound, the receiver is capable of being much smaller than similar wake-up receivers that respond to radio signals, while still operating at extremely low power and with extended range.
"As technology advances, people use it for applications that you could never have thought of. The internet and the cellphone are two great examples of that," said Rekhi. "I'm excited to see how people will use wake-up receivers to enable the next generation of the Internet of Things."
Once attached to a device, a wake-up receiver listens for a unique ultrasonic pattern that tells it when to turn the device on. It needs only a very small amount of power to maintain this constant listening, so it still saves energy overall while extending the battery life of the larger device. A well-designed wake-up receiver also allows the device to be turned on from a significant distance.
However, Arbabian added that the designing these electronic devices posed a number of challenges, such as scaling down wake-up receivers in size and power consumption while maintaining or extending range.
"But this challenge is worth pursuing," he said. "Because solving this problem can enable scalable networks of wake-up receivers working in our everyday environment."
Rekhi added that regardless of whether this specific ultrasound wake-up receiver becomes a standard design in the global device market, it's "likely wake-up receivers of some kind will be integrated into commercial applications soon".
The group is presenting the work at the International Solid-State Circuits Conference on 14 February.
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