Imagine a Sci-Fi title with this scene: At the last moment, some critical battlefield information is transmitted by a huge, bright and colorful beam of plasma antenna that shines the ground like Sun at night. It would make a spectacular and impressive scene of SFX and CGI, just like the SFX of the wrapped engine in the new Star Trek..
> during the early days of mobile phones
Probably not a good idea, in its original form, it requires a lot of power from the mains to maintain its arc discharge, which is what turns it into an antenna, kind of like a vacuum tube that needs a constant heating power. But Wikipedia says antenna-on-chip is possible, which is quite interesting.
An arc discharge is a hot, high current density process. [1] The discharge in a fluorescent lamp is a glow discharge: low current density, moderate temperature and extended volume. [2]
The first article gives fluorescent lights as an example of modern usage of arc lighting... The second article distinguishes between glow discharge and arcing.
One of my university lecturers, John Rayner, worked on developing these back in the day. Managed to track down a paper he published on it which is quite interesting: https://ieeexplore.ieee.org/document/1291644
Does anyone know how stealth fighter aircraft are able to incorporate radar hardware that doesn't act like a giant retro reflector? Putting a radar array on the front of a stealth fighter just seems like painting a giant bullseye on it, even if it's not emitting.
I wonder if something like this could already be in use, since it becomes invisible to radar as soon as the plasma generator is turned off?
I've never worked on stealth aircraft, but energy has to travel from the transmitter, through the aircraft's radar cover, off the array itself, then get back through the cover and back to the receiver.
There are probably ways to filter for specific RF frequencies on the cover so only those in specific bands can get through, then the array itself might absorb some portion of the energy that gets through. The array also might be at an angle so waves are reflected in a different direction, or there might be radar absorbing material placed in specific spots that helps minimize reflections. I think the arrangement of elements in the phased array itself could also lead to reduced RCS at certain angles. Again these are just educated guesses, I would imagine the details are classified.
I'm not exactly versed in the subject, but going off of a recent class on wireless transmissions, perhaps they instead use lots of small transmitters/receivers along the hull and rely on post processing to piece that together.
I'm not antenna knowledgeable nor plasma knowledgeable.
Is there a layman's explanation about what the advantages / why there are advantages here?
It talks about turning off the plasma antenna, is that any different than simply not using a regular antenna? ... or what they mean by stealth or "resistance to electronic warfare and cyber attack".
Hard-wired antennas can be detected by their shadows and reflections in the RF bands. Additionally, unless they are hardened against it, extreme RF energy, as might be generated by an EMP or by a highly-directional attacking antenna, can damage circuits connected to the receiving antenna.
When the plasma antenna is turned off, it stops existing. There's nothing there to attack or detect.
A possible future advantage would be shaping the plasma with magnetic fields, to create customizable antenna geometries, or geometries that electrically extend beyond the physical bounds of the equipment. Imagine using a laser small enough to fit in a backpack to create a 1/4 wave antenna long enough to transmit or receive at 30 kHz, with length 2.5 km .
You could create a plasma antenna 2500m long, send a message to a submarine 150 m below the surface, then it just disappears when you turn it off.
What a cool visual. Setting up a small beacon like object on the ground, standing back a couple hundred feet, and then a beam of bright blue light bursts several kilometers into the air, sending a quick burst of data while the capacitors powering it can keep it alive.
If using multiple converging lasers, the antenna need not be connected to the equipment. Two lasers could ionize the air in a line 2500m long, and a third could excite the center of it in a modulated fashion. That would be transmit only, unless you had some way to measure the energy levels at that center point from a distance.
It would be unlikely to glow brightly enough in the visual spectrum to see in the daytime, but it would be pretty cool at night.
Normally antennae are constructed out of solid materials. The plasma is controlled by electricity, so the gain characteristics can be rapidly controlled and dynamically tuned in real-time (possibly).
For normal people... pretty much nothing. You need power to keep the plasma hot, it's a safety hazard, and it's not cheap. For electrically-small antennas it looks like it might be slightly more efficient than a wire antenna of the same size (or slightly smaller than a wire antenna of the same efficiency) but most of the advantages listed pertain to military applications, and that seems to be who's driving the research.
I guess with a metal antennae you have a permanently reflective surface, AIUI once one of these are disabled they become basically radio-transparent again, which means less of a blip on radar
It's tunable for one, and it might be very fast to tune. At very high frequencies these are targeting (>50ghz), making an antenna suitably wideband to cover the entire bandwidth of some service is difficult and might result in a compromised antenna.
For security applications, the ability to turn it off is kind of nice; no antenna = no backscatter. OTOH how stealthy can a plasma antenna be when it is on?
Slightly OT, but there was no image in the page, so I scrolled down to the bottom and clicked a link in the "See also" section labeled "Article with image". The article had no image of a plasma antenna. What gives, Wikipedia?
The picture was there [0], but later livescience.com updated the website and it's gone due to link rotting. Even worse, archive.org didn't have the image archived (but the "zoom picture" text can be seen). Wikipedia is one of the most affected website by link rotting.
If you look at the thermal analysis, it is incomplete. They are only considering the thermal noise of the reflector. The noise temperature of an antenna is a function of temperature AND aperture efficiency, with the latter set by the conductivity of the reflector. Plasma is not a great conductor (compared to metal), as is shown by the nested antennas. High performance satcom (e.g. NASA DSN) not only cool the electronics, they cool the feeds also.
There is another paper where they show a tube covering a LNB. Looks like some BS. I don’t see any actual measurements of noise temperature (which are very easy to do).
I didn’t see any of the papers published in IEEE APS.
I design antennas for a living, and this sets my BS detector off, and it did 10 years ago too. They look fine for TX (the patterns look good), but the noise data is conspicuously absent.
Here is another noise analysis, but again it is incomplete. Just show some measurements.
If you look at plasma attenuation of a reentry body, it’s about 30 dB. Even a thin sheet of foil or perforated screen is way more (> 100 dB).
They just need to hook an antenna to a spectrum analyzer (with low noise path) and measure the noise density. If it is anywhere slightly above -174 dBm/Hz, then it is not going to function well as a satcom antenna.
That picture they show of the tube taped onto the LNB feed, they say it “intercepted” the signal. Do they mean it blocked it? Sure, it will if the plasma is conductive enough, but it should also drop the noise coming out of the receiver. Maybe it swamped the receiver with noise. Can’t tell. If they can pattern the lower frequency antennas, they can certainly take the time to do some noise measurements.
Maybe the issue is exciting the plasma, and that is noisy. I’d think you couldn’t do it with pulse excitation unless you limited the rise time. You could do it with CW, say a magnetron, way outside your operating band.
Can someone wire one to a guitar and pair it with a rydberg vapour cell as the recieving antenna, so the audiophile community can finally have something to justify their pricing.
The Gamechanger Audio Plasma pedal uses a plasma arc tube to generate overdrive. It's kind of gimmicky, but also ridiculously cool - it's inherently noise gating, because the arc extinguishes at low signal levels.
Find myself wishing such tech was prevalent during the early days of mobile phones and massive external aerials, but that's just the inner Jedi in me.