"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."

Comments

How does a disappearing antenna help?

[explosivejared]

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:How does a disappearing antenna help?

[TaeKwonDood]

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.

Re:How does a disappearing antenna help?

[Chrononium]

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).

Non Slashdotted Link

[eldavojohn]

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.

Not if you fly if from a stealth-plasma flagpole!

[wsanders]

(Sorry ham radio nerd humor.)

Disguise it as a stealth-plasma flagpole and proudly fly a red-white-and-blue flaming sheet-o-plasma flag! Has the added advantage of shocking the hell out of any pot-smoking hippies who try to burn it!

Lots of problems with this article

[compumike]

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.)

--
Microcontroller kits for the digital generation.

I remember these things.....

[DavidKlemke]

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.

It is stealthy

[Dan East]

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

embassy spying technology?

[SethJohnson]

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