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Devices Connect with Borrowed TV Signals, and Need No Power Source | MIT Technology Review

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The devices communicate by varying how much they reflect—a quality known as backscatter—and absorb TV signals. Each device has a simple dipole antenna with two identical halves, similar to a classic “rabbit ears” TV aerial antenna. The two halves are linked by a transistor, which can switch between two states. It either connects the halves so they can work together and efficiently absorb ambient signals, or it leaves the halves separate so they scatter rather than absorb the signals. Devices close to one another can detect whether the other is absorbing or scattering ambient TV signals. “If a device nearby is absorbing more efficiently, another will feel [the signals] a bit less; if not, then it will feel more,” says Gollakota. A device encodes data by switching between absorbing and not absorbing to create a binary pattern.

The device gets the power to run its electronics and embedded software from the trickle of energy scavenged whenever its antenna is set to absorb radio waves.

The backscatter communication technology was developed by Gollakota with Smith and David Wetherall, also a University of Washington professor, along with grad students Vincent Liu, Aaron Parks, and Vamsi Talla. A paper on the technology won best paper award at the ACM Sigcomm conference in Hong Kong this week.

I love the concept of a device that is an "energy scavenger". Brilliant.

good finds!

So energy scavenging devices are possible? I mean, this sounds sci-fi to me.

occam's razor of energy?

Maybe. It just seems like it takes energy to scavenge energy.

A crystal radio (no battery required) is an example of an "energy scavenger".