Researchers develop stealth radar system
By Donald Melanson 
posted June 28th 2006 9:42PM
posted June 28th 2006 9:42PM
Researchers at Ohio State's ElectroScience Laboratory say they've created a radar system that that is virtually undetectable when used, and able to penetrate solid walls to boot -- no doubt a significant boon to military, law enforcement, and disaster rescue operations. The radar works by scattering a very low-intensity signal across a wide range of frequencies, effectively disguising itself as random noise, but apparently not actually interfering with devices because its bandwidth is much broader than the signals it's hiding in. Although it's hardly the first to pull off wall penetration, the entire radar system can be built from components totaling less than a hundred bucks. But hold up before you run out to Radio Shack, because it shouldn't come as much surprise that they aren't providing detailed DIY plans. In fact, it sounds like those industrious Ohioans already got this system patented and are looking to license the IP -- so cheap gear or not, when it comes to the tech you gotta pay up or shut up.[Via Physorg]
"not actually interfering with devices because its bandwidth is much broader than the signals it's hiding in"
Whoa, sorry, I've gotta call BS on that. First off, bandwidth really doesn't have anything to do with whether or not it interferes. Also, you can't "hide" in signals.
Note the article says "Almost all radio receivers in the world are designed to eliminate random noise". Again, I call BS on the "almost all" part. I'm going to point out most anything that uses RF, and is not directly attached to a computer. TV antennas, walkie-talkies, Amateur Radio communications, etc.
I'll also point to the FCC rules for interference, and leave it at that.
Actually, bandwidth does have a lot to do with interference. The wider the bandwidth, the less power there is in any particular band. That makes the signal less likely to interfere with other signals, and it also makes the signal harder to detect because it does indeed "hide" in the noise.
First glance, it sounds like they're applying spread-spectrum principles to radar. Interesting. Makes sense, really. Of course, they could also be doing something more subtle. For example, it could be something as simple as a broader bandwidth for the signal. Particularly the claim about "hiding" in other signals and being indistinguishable from noise, which is the point of spread spectrum radio.
Shadyman, actually spreading the signal over a wide bandwidth does relate to interference. The point is that you're outputting less power on any given frequency than a narrower-bandwidth transmitter of the same total power. So if you have a narrower-band signal of some kind that fits inside the bandwidth of the radar signal, the wider-bandwidth radar will put less energy into the other signal's band than the narrower-bandwidth radar would, again assuming the same total power for both radars.
Sure, Chris. Beat me to the punch with a more concise explanation, why don't you!
It's called "chaotic radar". A google search on those terms will give you plenty of information.
May be they're using UWB (Ultra Wide Band) technology.
It sends signal through very wide band. You usually can't just send signal through wide band because all of them are property of some company which paid huge amound of money for them. (like.. 102.7MHz?)
But UWB allows the signal to "hide" in the noise by sending very weak signals so they can use the bandwidth w/o interfering with other signals.
I just took basic communication class so I may be incorrect.