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"Stealth" Plasma Antennas
eldavojohn writes "There's a new antenna that consists of plasma and essentially vanishes when you turn it off. While it may seem to not have many uses in the commercial world, it is very important to military personnel who risk detection or for anybody wishing to avoid signal jamming."
The article briefly claims the plasma attenna can be adjusted to react to the jamming. Independent feature of the ability to disappear.
When I submitted this story, I submitted the story from PhysOrg and I'm not sure why they changed the link. That poor blog didn't stand a chance. I guess they must do that to more randomly distribute their news sources or make it look like they aren't playing host to some PhysOrg worker trying to generate more traffic. Oh well, enjoy a usable link anyhow.
My work here is dung.
I read this in new scientist years ago:
http://www.newscientist.com/article/mg16422141.000-now-you-see-it---.html
Because it's a plasma antenna, it's tunable on the fly. No jamming tech ( though it will surely follow ) works on every f at once. The invisibility is just because it shuts off so then is basically inert.
Antennas are not stealthy. They have a radar signature, but glass has a minimal radar signature. So the tube should not be as non-stealthy as attaching a chunk of metal to an otherwise stealthy piece of equipment.
--The FNP
'Stealth' Antenna Made Of Gas, Impervious To Jamming Submitted by News Account on 12 November 2007 - 2:58pm. Physics
A new antenna made of plasma (a gas heated to the point that the electrons are ripped free of atoms and molecules) works just like conventional metal antennas, except that it vanishes when you turn it off.
That's important on the battlefield and in other applications where antennas need to be kept out of sight. In addition, unlike metal antennas, the electrical characteristics of a plasma antenna can be rapidly adjusted to counteract signal jamming attempts.
Plasma antennas behave much like solid metal antennas because electrons flow freely in the hot gas, just as they do in metal conductors. But plasmas only exist when the gasses they're made of are very hot. The moment the energy source heating a plasma antenna is shut off, the plasma turns back into a plain old (non conductive) gas. As far as radio signals and antenna detectors go, the antenna effectively disappears when the plasma cools down.
This prototype plasma antenna is stealthy, versatile, and jam-resistant. Credit: T. R. Anderson and I. Alexeff
The antenna design being presented at next week's APS Division of Plasma Physics meeting in Orlando consists of gas-filled tubes reminiscent of neon bulbs. The physicists presenting the design propose that an array of many small plasma elements could lead to a highly versatile antenna that could be reconfigured simply by turning on or off various elements.
- T. R. Anderson and I. Alexeff 2007 APS Division of Plasma Physics annual meeting November 12, 2007
Letter To Iran
In a normal antenna, electrons in the metal slosh up and down, accelerated by the electromagnetic fields that it's receiving (or transmitting). In this case, I could use the same description: electrons slosh up and down, driven by the EM fields.
The idea that this could lead to a reconfigurable antenna is a bit farfetched, as it would require that the driving bias electrodes be able to totally float at RF frequencies. Just like a neon sign, or a fluorescent light, you're going to have to keep a large voltage across these to get them to light, so it'll be tricky to use it as a receiving antenna in particular.
Take a look at another project, Talking Lights. This uses conventional fluorescent lights (hey, a plasma!) with a modified ballast to transmit data at serial-link speeds.
The "jam-resistance" doesn't make any sense. If it can receive signals, it can receive signals, period. At the point of the antenna, the desired signal and the jamming signal have already been mixed. The antenna itself can't help you out. (Clever frequency-hopping or other schemes can, though.)
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Microcontroller kits for the digital generation.
Back in my university days I had the pleasure of being taught by a physicist turned engineer who was actually working on one of these things. The trouble with traditional antennas is their giant radar footprint and traditionally they solved this problem by flopping the antennas up and down when they needed to send signals. Not the most graceful solution so they started looking for alternatives. We had one of the prototypes of these things in the plasma instrumentation lab and it was pretty adept at sending some small signals. The great thing about them is their tunability. Just like any kind of woodwind instrument if you change the length of the tube (imagine a giant piston that's got plasma in it) you change the resonant frequency. My lecturer referred to it as playing the plasma trombone. Good to see these things finally making their way through to practical uses. I was always hoping my crazy lecturer's tinkerings would be used someday.
The Refined Geek - Technology, Finance, Space and everything in between
One very simple way to counteract jamming is to note that the jammer is not omnipresent. That is, the jamming source is often only present in a small radian-angle of the antenna's radiation sphere. Therefore, you can counteract jamming by configuring your antenna to place a null in the direction of the jammer (i.e. ignore the annoying little kid) and radiating elsewhere. Alternatively, if you know where you want to either transmit a signal or receive a signal, you can create a beam to point in that direction by reconfiguring your antenna. In both cases, it is usually standard practice to use an array of antennas. This invention (and no, it's not really a new idea, but perhaps the engineering makes it more reliable or easier to manufacture than in the past) allows you to place a large antenna array on an aircraft without permanently increasing the RCS of said aircraft, since the antennas only exist when you charge up the plasma. A large antenna array can create a narrow beam and place several nulls using conventional technology. All of this stuff exists today, so these plasma antennas just need to replace metal antennas and away you go. The really interesting application of these antennas could actually be to create 3D reconfigurable antennas using DC-magnetic fields (kind of like a CRT, but with more magnets).
yeah.. all ruby is, is aluminum oxide. in crystalline form. the created rubies / emeralds / sapphires are essentially identical to their natural counterparts in composition and structure these days..
it can be synthed without too much trouble, but the cost of an alum.ox. antenna would still probably be pretty high, though. while it's cheaper to create a gem in the lab than buy a wild one, that's just for gem-sized pieces. it'll cost a fair shake regardless if you're talking about FEET (or METERS) rather than inches or mm.
... still waiting for this free-as-in-beer free beer I keep hearing about.