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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."
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.
"File to fit, pound to insert, paint to match" - Aircraft Maintenance 101
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...
"File to fit, pound to insert, paint to match" - Aircraft Maintenance 101
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.
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?
Everything I write is lies, read between the lines.
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.
When I was a kid, we used drums to communicate. We didn't even have string!
Now get the hell off my lawn.
Interesting comments. You mentioned RF power functions. The main function for radio, also called far field, is that power drops with the square of distance.
I'd like to point out card readers do not work using radio waves, not like these devices do. At distances less than about 1 wavelength, the primary effect is what's called "near field", commonly referred to as induction. This is the same way transformers work. Near field power drops at distance to the SIXTH power. That means that while it's very strong within a few millimeters, it basically dissapears within a few centimeters or meters.
The new devices are using RADIO energy from arbitrary far away sources. Card readers use near field induction, a completely different mechanism.
I told the kid (about 10 yo at that time) of friends about the can-string-can phone and we made one. I didn't expect that he would play with it for more than a few minutes. But to my surprise I noticed on later visits that the string phone was used when playing with friends. I've even noticed that it got repaired or even rebuild at some time. However, I think that he would never have learned about it if I didn't told him. Many parents are not enough involved with their kids to tell them about (or point them to the right books, web sites, ...) about these easy to try experiments.
Most kids would love to do these kind of experiments, but they need some guidance to get started. But it's easier to just give them a game console so they ask for even more parent's attention :-(
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weinersmith