Wireless Devices Go Battery-Free With New Communication Technique

melios sends this quote from an University of Washington news release: "[E]ngineers have created a new wireless communication system that allows devices to interact with each other without relying on batteries or wires for power. The new communication technique, which the researchers call 'ambient backscatter,' takes advantage of the TV and cellular transmissions that already surround us around the clock. Two devices communicate with each other by reflecting the existing signals to exchange information. The researchers built small, battery-free devices with antennas that can detect, harness and reflect a TV signal, which then is picked up by other similar devices."

Comments

The Technology is Not New

[bobbied]

This is not new technology.

Toll Tags and other RF-ID devices have been using "back scatter" techniques to capture energy to transmit with for decades. The reader device provides RF energy that is captured by the tag charging up a capacitor enough to send a short burst of data back to the reader. I saw this being done during a Job interview in Dallas sometime in the 90's and was impressed with the idea. I was even more impressed that it worked well enough to actually be in use on various tolling systems. Still remember the test rig they had with the tags mounted to the ceiling fan blades as being decidedly low tech, but wonderfully effective.

The application might be a bit different, but the technology is NOT new.

Re:The Technology is Not New

[bobbied]

Getting power from an external RF source is not new. Being able to get it from ambient RF sources is not new either.

The tags I saw where charging whenever RF was available. The tag didn't know or care if the power came from the reader or not. The goal was to keep charged and "ready" for the data burst when the reader asked for it. Any RF source was suitable for charging and that the reader provided power was merely a matter of making sure there was enough power when needed. So for reliability sake you put some RF power out to charge the tag before you need it to transmit the data you want, but they still charged from anything else they picked up.

So what does it matter where the background RF comes from? Capturing energy from RF is certainly not new. Using such power to communicate is not new either.

Re:The Technology is Not New

[adolf]

Actually, passive key cards do store the energy for later use.

"Later" happens to be measured in microseconds or so, but it's still later (much, much later in computer terms).

First, the antenna inside of the card is used with a rectifier and a capacitor to make DC voltage to power an IC from the RF energy radiated by the card reader. Once the voltage is high enough (which cannot occur instantaneously), that IC then uses the energy stored in its capacitor to send its ID string over the same antenna that was part of a power supply a brief moment earlier.

And like anything else RF, distance is largely a function of radiated power and receiver sensitivity. Cards and readers generally only work within a few inches merely because that was one of the design parameters, not because that is the maximum attainable using the technique:

Improve the performance of the card (more capacitance combined with a beefier RF section), and/or increase the sensitivity of the reader (using a higher-gain antenna and/or lower-noise electronics), and functional operating distance is increased accordingly.

Re:The Technology is Not New

[__aaltlg1547]

What's new is they're working with very low power levels. I've never seen a backscatter system that can work with so little incident power.

Re:New???

[bobbied]

Not exactly the same thing, but receiving RF without power has been done for about as long as RF has been received... Actually... Exactly as long as RF has been received. Crystal Radios where how this whole "Let's communicate by radio waves" thing got started...

Re:New???

[mcl630]

Not quite the same. Crystal radios can't transmit information, only receive it, while this can both transmit and received. In the sense that they're powered only by the RF received, they are similar.

Re:it is new... in a way.

[ls671]

Peer to peer analogy? If not enough people seed with devices hooked up to power sources, the system will fail.

Also, I remember that they caught a guy hijacking power from high power lines without touching the wires. He was doing it simply by induction and the power line was close to his barn. The electricity company noticed a power leak and this let to an investigation resulting in him being convicted even if he never touched the wires.

Now, how will the tv and radio stations react when they notice their signal get weaker because a bunch of devices draw power from their signal?

Re:Scientifically, fine, but not good in principal

[Anonymous Coward]

I've got no objection to such research scientifically speaking. However, I am staunchly against any form of computation or communication that someone else can simply pull the plug on. Switch off the microwave carrier signals and these systems are dead. Wouldn't that be scary as hell to rely on?

There's degrees of reliance. For a TV remote or PAN application, not scary at all. For a mobile phone that one's life might depend on, somewhat scary.

Before I used such tech I'd want it made legal to generate my own background radiation at home. That's currently illegal by the way.

Sorry, but we have these little thing called the ISM bands, perhaps you've heard of them. (There's one at 2.4GHz, WiFi and bluetooth use it.) You're perfectly allowed to generate RF in these band. You're also allowed to generate unlicensed emissions in many other bands, subject to strict power limits that will still likely be enough (at short ranges) for these devices to work. (I agree with you, at least on a broad view, about what's wrong with the FCC and our current spectrum ownership policies, but you don't help things by overstating the restrictions....)

I'm not saying the eventual commercial implementation of this idea won't be intentionally crippled to rely on frequencies that are more tightly controlled, precisely to provide an off switch, but until/unless they are, your wholesale indictment of the tech is premature. The natural choice for this tech, outside monopolistic/control-freak pressures, is to have it use several options including one of the heavily-used ISM bands, because there's a lot of available energy in them, and (unlike, say, broadcast TV frequencies) they're used even out in the country. (Mobile phone networks are another obvious choice, with better rural penetration than TV, but there's still sufficiently remote places with almost no mobile phone signal, and people in thes places still run WiFi APs connected to their landline internet.)

Also, learn the difference between principle and principal. Botching it as you did makes you look like a moron.