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Communications Hardware

"Stealth" Plasma Antennas 169

Posted by ScuttleMonkey from the no-you-see-it-now-you-don't dept.
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."
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"Stealth" Plasma Antennas More

"Stealth" Plasma Antennas

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  • How does a disappearing antenna help? (Score:4, Insightful)

    by explosivejared ( 1186049 ) <hagan@jared.gmail@com> on Monday November 12, 2007 @06:39PM (#21329275)
    How does having the antenna "disappear" effect it's ability to circumvent jamming? The article is apparently being slashdotted as I type this, so I'm just curious.

    • Re: (Score:3, Informative)

      by another_neophyte ( 1050364 )
      The article briefly claims the plasma attenna can be adjusted to react to the jamming. Independent feature of the ability to disappear.
    • Yeah, I don't get that either. And the tube the gas is in is still around.
      • It was tested with 100% accuracy in Los Vegas. Seriously though, isn't emitting light the opposite of stealth?

    • Re:How does a disappearing antenna help? (Score:5, Informative)

      by TaeKwonDood ( 1171129 ) on Monday November 12, 2007 @06:46PM (#21329365)
      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.
      • What are we talking about jamming? Radio, microwave, what?
      • Still, if you are transmitting voice on let's say 150 Mhz and someone is transmitting a high pitched whine (taking up more bandwidth, thusly...16khz or so) at a higher amplitude than your voice transmission, it's gonna get cruddy. Even FM gets F!'ed up by this. Then again, all you have to do is change frequencies, but I don't see where attenuation comes in handy for defeating a broadband jammer.

        Same principle would apply to airborne data transmission, I would think. Correct me if I'm wrong, I only renewe

        • Re: (Score:2)

          by stevew ( 4845 )
          I don't disagree with you - and I'm a "good" ham (whatever that means ;-)

          I don't believe these claims - they're just stupid. Anti-jam? For instance - you want the antenna to disappear? If we're talking on a HUMMV - what the heck. Just turn the radio off???? That is how you disappear electronically.

          As for the noise crud the plasma generator and the high voltage will make - maybe it can be filtered, but think of all the juice you're wasting creating the plasma field!!! A hunk of metal seems a more effici

      • Re: (Score:2)

        by AB3A ( 192265 )
        There are lots of antennas that are tuneable on the fly. Diode switching can do that. So can mechanical antennas. At microwave frequencies, conventional antennas can be very broad-banded.

        Oh, and jamming actually DOES work on many frequencies at once. Ever heard of repeating jammers? Something else to consider: Jammers used against radar don't need to be as powerful as the radar. They only need to cover up the echo. The echo dies off according to the distance to the fourth power. The more powerful t

    • Re: (Score:3, Informative)

      by The FNP ( 1177715 )
      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
      • Isn't plasma hot? ie:
        1. Shoot radar-guided missile
        2. Shoot heat-seeking missile
        3. ???
        4. Kaboom!

        • Re: (Score:3, Insightful)

          by mapsjanhere ( 1130359 )
          Yes - and no :)
          The gas is hot, but at very low pressure. So the amount of energy transmitted to the glass container surrounding it is minimal, and could be further reduced by active cooling. So the second your incomings are detected and the antenna shuts down it becomes invisible to both the RF and infrared seeker.
      • I don't quite get the usefulness of this thing either - when it's turned on, there's bright glowing plasma, and when it's turned off, even though it doesn't have a long metal piece, it still has a lot of metallic support machinery, plus it's a glass tube that you need to haul around carefully instead of a metal antenna or rubber ducky that you can bang into things.
    • If it is performing as an antenna then it will have the same RF characteristics as a physical antenna and so must be open to jamming.

    • Re:How does a disappearing antenna help? (Score:5, Informative)

      by Chrononium ( 925164 ) on Monday November 12, 2007 @07:21PM (#21329799)
      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).

    • An old idea (Score:2, Interesting)

      by Anonymous Coward
      This is an old idea. Look in Kraus, Antennas, Third edition. Section 21-29. Also see patent 6657594. The point is the RCS of the antenna is lower when the plasma is off, they efficiency of this type of antenna isn't that high.

    • Re: (Score:2)

      by omeomi ( 675045 )
      How does having the antenna "disappear" effect it's ability to circumvent jamming?

      I'm a bit foggy how it "disappears". Last I checked, you need some type of container to shape plasma into a cylinder, so while the plasma may disappear, the giant glass tube presumably will still be there...and why does the author keep calling plasma a gas? Yes, you get plasma by superheating a gas. You get gas by heating liquid. Doesn't make gas the same as liquid. Plasma isn't the same as gas either.
      • Hmm... boiling a gas to get a plasma. Interesting meme.
      • The glass tube doesn't dissapear. Think of a fluorescent tube: when it is lit, it radiates light and non-visible EMR, but when it's off, it doesn't. Now ideally, a metallic antenna won't either, but since it's a conductive material, nearby electric and magentic fields will induce magnetic and electric fields which *could* be detected or, more practically, a metallic antenna will reflect EM waves that strike it whereas glass won't (or at least will do so to a far lesser extent).
        A far more realistic problem

        • Re: (Score:2)

          by omeomi ( 675045 )
          shielding the antenna in some kind of enclosure.

          Some sort of metallic material, perhaps! ;-)
          • Of course! We must put the plasma antenna inside a Faraday cage to protect it from damage! I tip my hat to you, good sir (or madam). ;P

    • Re: (Score:2)

      by Tiger4 ( 840741 )

      How does having the antenna "disappear" effect it's ability to circumvent jamming?

      A metal antenna can be detected just like any other large metal object. When you kill the juice to this, it just disappears, so you don't have any large metal bits to stow.

      What gets me is how the plasma isn't a signal emitter in its own right. I mean, we are talking electric arc discharge, like an neon sign, like a spark gap, like lightning. I had always thought an electric arc was a broadband RF transmission. That should be detectable in every direction.

    • Re: (Score:2)

      by geekoid ( 135745 )
      The article answers those questions.

  • Non Slashdotted Link (Score:5, Informative)

    by eldavojohn ( 898314 ) * <eldavojohn@noSpAM.gmail.com> on Monday November 12, 2007 @06:42PM (#21329315) Journal
    When I submitted this story, I submitted the story from PhysOrg [physorg.com] 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.
    • Much appreciated, but still the physics seem a little weak. I still am not getting how changing the composition of the antenna will prevent jamming. Both articles fail to articulate this very well.

      • Re: (Score:1, Interesting)

        by Anonymous Coward
        Greetings,

        It doesn't really prevent jamming, though it does give them a variable antenna, by tuning the plasma, thereby improving their ability rapidly change radio frequencies etc. This give them the ability to reduce the affects of single band jamming and even some multi-band jamming. It actually seems pretty clever, though, I really fail to see it's battlefield value as there will be a tremendous amount of heat given off by the plasma field. Now shipboard and some amored cav use
    • You can view it as an electrically switchable conductor. Turn the power on and you have a conductor. Turn it off and you get an insulator. The problem is that it takes power to maintain. As long as you have adequate power, you can make a conductor. If you have lots of power, you can ionize atmospheric pressure air, but we do mean lots of power. At low pressure, you need less power, but you have the corresponding issue of fragility of the supporting structure, which must be both strong and insulating.

      An al

    • The original link works for me

      '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 chara
      • FINALLY !!! One step closer to getting a working light saber !

        Wonder if this works for wifi antenna. Would make it easier to see the people stealing my neighbors wifi signals.
    • I submitted this link but it says 'pending', so maybe they liked your writeup and my link. It's mashably terrific. I think we could all live without a physorg monopoly for one day.
  • If it helps with signal jamming, I want it integrated into my cell phone! What do you mean it doesn't have commercial viability?

    --The FNP

  • Not News (Score:3, Informative)

    by Anonymous Coward on Monday November 12, 2007 @06:44PM (#21329341)
    I read this in new scientist years ago:

    http://www.newscientist.com/article/mg16422141.000-now-you-see-it---.html [newscientist.com]

  • TFA (Score:4, Informative)

    by DumbSwede ( 521261 ) <slashdotbin@hotmail.com> on Monday November 12, 2007 @06:49PM (#21329405) Homepage Journal
    '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

    • Re: (Score:2)

      by QuantumG ( 50515 )
      So what's you're saying is that this conversation is no longer fiction:

      Radio Operator: Sir! I can't get through to base!
      Officer: damn, they must be jamming our transmissions! Try inverting the phase polarity!
      Radio Operator: That did it! I have communications.. here..
      Officer: General, the enemy is capable.

    • Re: (Score:3, Insightful)

      by Brandon30X ( 34344 )
      These antennas sound interesting, reconfigurable and all that, but I am guessing that their noise performance must be awful. And I mean electrical noise not audio noise for those out there who are confused. Usually in an RF system you want as little noise up front as possible, and noise goes up with temperature. So this is an antenna made of very hot plasma as the very first element in the receiver system.

      I could be wrong, I didnt RTFA.

      -Brandon

      • Re: (Score:2)

        by afxgrin ( 208686 )
        I keep thinking that the accelerated gas atoms are going to sputter the electrodes. The last thing I'd want in an antenna is having to carry around a gas cylinder just to maintain the operating pressure. Because as whatever gas is used, the atoms are going to embed themselves into the electrode lowering the pressure. This maybe less of an issue if they drive it with an AC source rather than DC, but it's certainly something to consider. Awesome that someone is doing this though, I was thinking about this

  • Lots of problems with this article (Score:5, Informative)

    by compumike ( 454538 ) on Monday November 12, 2007 @06:51PM (#21329425) Homepage
    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 [talking-lights.com]. 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.)

    --
    Microcontroller kits for the digital generation. [nerdkits.com]
    • Or using multiple antennas so you can do a spatial analysis of the signals.

      Do it right, and you end up receiving the signal you want, and knowing exactly where it is being transmitted from, while also receiving the jamming signal and knowing exactly where THAT is from.

    • embassy spying technology? (Score:5, Interesting)

      by SethJohnson ( 112166 ) on Monday November 12, 2007 @10:49PM (#21331545) Homepage Journal


      Install a listening device in an embassy meeting room. Records many weeks of conversations. Does not broadcast. Also has a radio receiver.

      Prior to an electrical storm, drop a package on the roof using a rapid-descent parachute. It looks like a chimney or AC unit, with a large pole on top that functions as a lightening rod. The box sends a signal to the inside recorder that tells it to broadcast a burst of encrypted data to the box then when lightening hits the pole, it becomes a plasma attenna that can broadcast the data over a long distance. Oh, and the electricity from the lightening powers the whole operation. Then the box self-destructs on the roof.

      Seth
  • OK, so you don't have a big metal antenna...Instead, you have a big structure built out of evacuated glass tubes resembling Neon tubes.

    And you're going to take this out on the battlefield?

    Now, the concept of changing the resonant frequency of the antenna by activating different individual elements is kinda cool, but this doesn't look stealthy at all.

    /frank
    • It is stealthy against antenna-detection tools which operate on EM spectra quite different from visible light.

      It's kind of how a stealth bomber is quite easy to notice if you just look upward -- it is made to fool radar, not human sight.

  • I remember these things..... (Score:5, Informative)

    by DavidKlemke ( 1048264 ) on Monday November 12, 2007 @06:51PM (#21329431) Homepage
    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.

    • Minor musical nitpick: (modern) brass instruments, such as the trombone, change resonant frequencies through changing the length of the tube. Woodwind instruments change effective lengths in ways that probably don't work so well in describing antennas.

  • Combat viable? (Score:3, Interesting)

    by djasbestos ( 1035410 ) on Monday November 12, 2007 @06:56PM (#21329491)
    The pic from TFA looks a bit dainty for combat use. I think a whip antenna is probably still more reliable and has a smaller radar signature for short range communication (IE a couple dozen miles). And the big ones, well, there's no hiding them.

    Plus that whole bright and hot thing tends to attract the attention of certain guided missiles and sensor systems...not good! Maybe if they paint the glass or something...at least the light problem is solved.
  • I reposted the article just above. The picture shows a glowing u-shaped florecent tube. By "disappear" I believe they just mean large radar return. Such materials are called PECs in radar parlance (Perfect Electrical Conductor). You will still be able to see the tube visually.

    In related speculation, I wonder if you could use the ION beam from a space probe's thruster (assuming Ion Drive of course) as an antenna. Of course since it wouldn't be parabolic or very directional it might be of limited use.

  • Switch now! (Score:2, Funny)

    by maciarc ( 1094767 )
    Everyone should go out an buy a new plasma antenna before they switch on Feb 17, 2009. After that, your old metal ones will have to have an adapter to work.
  • Yup totally undetectable, its not like the enemy has the equipment to spot the infrared thrown of by gas heated to super high energy levers or anything. So much harder to see then a metal pole.
  • If it needs glass tubes to work, its not like it will just 'dissapear', and would be a lot more fragile than a metal one. That might be ok for light use, but stick it out in the battlefield and i dont see it holding up for long.

    Might work disguised as a neon 'eat at joes' lamp for undercover work..

    It also mentions needing several 'segments' to prevent jamming. Couldn't this also be done with more traditional antennas?
  • This might have a small physical cross-section on radar, but I'm not sure that's enough to compensate for the plasma... ...I work in an electronics lab, and occasionally we use a sputtering system - which generates a ball of plasma to transfer ions from one surface to another. Anyway, point being, when we do this, the guys next door, who do a lot of RF measurements, go absolutely nuts - because we've just screwed all of their instruments and currently-running measurements. (Incidently, between them and th
    • I work in an electronics lab, and occasionally we use a sputtering system - which generates a ball of plasma to transfer ions from one surface to another. Anyway, point being, when we do this, the guys next door, who do a lot of RF measurements, go absolutely nuts

      Have you completed RF leakage testing? Is the RF screen in place in the quartz windows? Is the cable secure between the RF gen and the matching network? Is the RF gasket in place between the match and the chamber. There is no reason to have e
  • But can I use it for filesharing, and just disappear when the RIAA comes sniffing around?
  • Sure, it's hard to spot when you turn it off maybe... does that make up for the fact that it looks like it glows like a goddamn spotlight when it's turned on, or am I missing something?
    • Sure, it's hard to spot when you turn it off maybe... does that make up for the fact that it looks like it glows like a goddamn spotlight when it's turned on, or am I missing something?

      The demo unit is clear. The real unit has opaque paint.
  • The plasma is contained in a glass, neon light, like tube.

    I was picturing a 30-40' foot long spear of flaming hot plasma death that you could turn on your enemies to turn them into smouldering piles of charcoal....and radio in to mom at the same time!!!
    • That would be the Apple iPlasma phone. Not only can you make calls, listen to music, and watch videos on it, but you can extend the plasma antenna and kill people who are using ordinary cell phones. Especially the annoyingly talkative oblivious ones in restaurants, movies, or grocery lines.

      The iPlasma -- flaming death in a compact shape -- only from Apple. Note: We only accept cash, and only two iPlasmas to a customer, please.

  • Auto Electronics (Score:3, Funny)

    by Doc Ruby ( 173196 ) on Monday November 12, 2007 @08:26PM (#21330357) Homepage Journal

    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,

    Everyone who parks their car in NYC and other hostile environments wants an antenna that vanishes when you turn it off. Plasma probably wouldn't jam after a year of use like a retractable antenna, and might even clean the snow off your car, including the pile burying you from the street plows.
  • Well, the "stealth" antenna in the article is a huge, glowing tube. According to the article, the antenna is indeed made of "gas-filled tubes reminiscent of neon bulbs."

    I wouldn't call an neon sign "essentially vanishes" when it's turned off.

    There's no indication in the article that they can generate the plasma without a confining tube, but even if they could, like the Cheshire cat's grin without the cat, it would still be pretty conspicuous when it's on.

    Reminds me of an old cartoon in Computerworld, back i

    • Re: (Score:2)

      by aXis100 ( 690904 )
      Did you think that maybe they might put the neon antenna inside an opaque container? Also, the "stealthy" part refers to it's ability to hide from antenna detectors, not physical inspection.
  • sounds like it might find application in the area of phased-array radars.

  • It is stealthy (Score:5, Insightful)

    by Dan East ( 318230 ) on Monday November 12, 2007 @09:32PM (#21330867) Journal
    Metallic antennas are excited by EM radiation (radio waves) of a proper wavelength. In turn, the antenna will re-radiate (transmit) a tiny bit of that energy, although very weakly, which can be detected. This is totally passive, which is how it is possible to build a passive repeater by simply running a wire between two directional antennas. It is also the general principal of how RFID tags work.

    The stealth of this antenna is that it is non-metallic and will not react to EMF when switched off. It has nothing to do with how big the antenna is, or what color it is, or whether or not it emits light, which are all things people have been speculating about.

    Dan East
  • You cannot post an article with the words "invisible" or "disappear" willy-nilly! You must be precise! Do you know how many salivating geeks are about to be very disappointed by TFA?

    (The gas becomes non-conductive when it's off, so it's "invisible" to radar or something like that. The glass tube holding the gas is perfectly visible. It's not like some sort of light-saber thing.)
  • I'd love to see that antenna shatter during vibration tests. Any kid with a pellet gun can break that thing, so it sure won't be very useful to anybody nevermind the military.
  • So, it 'vanishes' when it is off? When it is on it lights up like a neon sign? I could be wrong - but a gigantic neon light antenna up in the air is going to be a pretty obvious target. The enemy is going to know exactly where you are. Also - they are going to know you are transmitting something - so they can start to jam/home in on your signal. How exactly does this prevent that?

    Also - I would love it if the enemy used this brilliant antenna design. You will be left flabber"gas"ted as I use my ultra-portab
  • I remember seeing this stuff more than 10 years ago. Being Australian the stuff I saw ten years ago was from an Australian University grant from the DSTO (military research organisation), with information that can be found at http://wwwrsphysse.anu.edu.au/~ggb112/ [anu.edu.au]

    In fact a Typical Fluroscent tube makes a reasonable HF antenna with its frequency dependent on its length. For those that think the glowing plasma makes the antenna detectable in the visible spectrum, its easy to have a material that is opaque in
  • In my mind, if you sell to the military, it's still commerce.

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