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Twisted Radio Beams Could Untangle the Airwaves
Urchin writes "The radio frequency spectrum available for wireless communication is becoming increasingly crowded thanks to new wireless technology. A solution to the shrinking space might be to put a spin on radio beams during their transmission, to produce a twisted beam, according to Swedish physicists. In theory, huge amounts of data could be sent in the pitch of the twist, which is distinct from the amplitude and frequency of radio waves — the features used at the moment to send information."
Damn, this is so obvious now. I should have thought this up years ago.
The Kruger Dunning explains most post on
Now we have "Spinnaz" for telecommunication geeks.
1. How practical is this technology? Could you mass produce cheap low power receivers to put in every car/computer/etc...? How complex is the transmit circuitry?
2. How resistant is this to atmospheric and other interference? In theory it should be pretty resistant, but in practice who knows.
Needing multiple antennas to get this done sounds like a rather big limitation to me.
I read the internet for the articles.
Do a barrel roll!
Sorry, couldn't resist.
Don't cross the streams.
The article appears to be referring to right or left circular polarization, as opposed to horizontal or vertical polarization. A horizontally-oriented dipole transmitting near a vertically-oriented dipole will be heard much more faintly - 20db+ quieter. Similarly, a left-polarized antenna won't interfere with a right-polarized antenna. But a circularly-polarized antenna will still interfere with a horizontally or vertically polarized antenna - it'll only be 3db weaker.
I install wildblue satellite internet and we have two type of transceivers right hand and left hand polarization. after rtfa I am curious if this is the same thing or something different?
lose != loose
There is a reason that FM is polarized in the direction it is: any other direction is relative.
FM is vertically polarized because that means that a car needs only have a vertical antenna to catch the signal, if they polarize it horizontally then the antenna on the car needs to rotate every time the car turns.
At least this is what I was told in my RF/microwave design class.
AFAIK (yes, I did RTFA), this is tantamount to adding another method of data transmission using more of the envelope. You still have the frequency being used and still have a portion of the carrier plus sideband transmitted, no matter what type or method of transmission is used. This may be used to embed something similar to a sub-carrier, or a unique identifier. More directivity and narrower beamwidth during point-to-point transmissions will do wonders to keep the RF floor down.
Don't spend your life lamenting your life.
The "In Soviet Russia" joke has already been inserted, so I'll go on to the next step:
The technique described is independent of amplitude and frequency in that it is based on polarization. Circular (clockwise and counter clockwise) polarization was used in Soviet and early post-CCCP Russian satellite communications. I had an article from ~25 years ago that showed how to alter a US type vertical/horizontal polarization low noise amplifier on a satellite receiving dish to pick up clock/counter signals. (The trick was to insert a teflon plate at a 45 degree angle to the vert/horiz signal; I tried it, it picked up the signals but I couldn't decode them with a US commercial receiver). One may feel free to speculate on the history of Sweden vs. Russia/CCCP and this claim by Swedish scientists to have 'discovered' this technique. There's no reason why satellites couldn't have had both kinds of polarization on board, except that each required its own transceiver. Todays' larger birds could carry both and help alleviate the Clarke orbit traffic jam. The same concept can be applied to terrestrial equipment, and in fact could have been used for years.
"I may be synthetic, but I'm not stupid." -- Bishop 341-B
Polarization has been known since about 1200AD when the Vikings used calcite crystals to navigate by. It also pops right out of Maxwell's equations.
It's been used to make directional radio antennas since about 1925.
It's been used to dynamically steer and polarize signals ever since phased-array radars came in use, circa 1965.
And no, you can't transmit huge amounts of information that way. Circular polarization is just a vector sum of two quadrature vectors. There's nothing you can do with a sum that is more information efficient than a single vector.
Yeah but who wants to pay extra to hear the same old shit? Wow, a higher quality feed of the same 10 songs that commercial FM radio plays over and over again.
Not to mention, digital radio fucks up adjacent channels, especially on AM. They really need to scrap AM like they did with digital TV (although that transition was far from perfect). FM is just fine. I don't think people really care about audio quality that much (why would
(-1, Raw and Uncut is the only way to read)
Shannon's law is a tricky piece of work. It doesn't actually tell you how much data you can transmit given a particular amount of bandwidth. It tells you how much data you can transmit given a particular amount of bandwidth and particular noise characteristics over a given channel.
Now, you can play various games with that. If you limit yourself to, say, frequency modulation, you just measure the noise, run it through Shannon, and get your result. But what if you polarize the signal and encode data in that? Have you broken Shannon's law? No. You can account for things like that by counting it as a separate channel, or by changing your noise estimate to account for the additional, independent modulation technique.
These guys' modulation technique is another independent channel.
The article does say it's probably not going to work very well for things like cell phones though, since you need an antenna array. It might be useful for things like microwave towers though.
Yes, you are, and no, they aren't.
This is about modulating the orbital angular momentum of photons, a property that wasn't even discovered until 1992.
Each photon can have an integer quantity of orbital angular momentum (0, 1, 2, 3...) without obvious limit (or in the opposite direction, -1, -2, -3...). In principle, and increasingly in experiment, it is possible to encode information by modulating the orbital angular momentum carried. This provides and entirely separate channel with its own bandwidth in addition to traditionally understood modulation. They're right to be excited about it; it has the potential of being just as big in scope as was the invention of radio.
See http://www.physics.gla.ac.uk/Optics/play/photonOAM/
Professional Wild-Eyed Visionary
See http://www.physics.gla.ac.uk/Optics/play/photonOAM/
Professional Wild-Eyed Visionary
See http://www.physics.gla.ac.uk/Optics/play/photonOAM/
Professional Wild-Eyed Visionary
They're using physics that wasn't even discovered until 1992.
See http://www.physics.gla.ac.uk/Optics/play/photonOAM/
Professional Wild-Eyed Visionary
Actually, broadcast FM is nearly always circularly polarized using a multi-bay antenna with a bunch of 3/4 circle center-fed elements, each with one end pointing up and the other down.
If you weren't aware of this, go look atop an FM tower with binoculars some day.
Good luck finding the published theory on these antennas, since they're all proprietary designs!
The determined Real Programmer can write Fortran programs in any language.
py|x(y|x)
This would increase X and Y, so doesn't violate Shannon's theorem. If memory serves, x and y are what determines a channel. This technique would be another channel... kinda.
Oh, and what you are really talking about is channel capacity. Not Shannon's theorem which is about optimal error correction.
Imagine a long solid metal pole.
Now imagine a theorem that describes the max. data that can be written on the surface of this solid pole.
Now imagine some smart guy comes along turns the solid pole into a tube. The tube is still the same length. but the surface area has increased, the max information has increased. The theorem would still be sound because the surface are increased.
I apologize for such a primitive example, it's only to illustrate a point not to accurately define EM theory~
The Kruger Dunning explains most post on
This article has a good explanation of the difference between Orbital Angular Momentum and Polarization of EM waves.
If you look at the cross section of a "normal" polarized EM beam, the electric field amplitude and direction at every point of the cross section are in the same phase - although that direction may be up, down, or rotate over time depending on the polarization.
In an EM beam with orbital angular momentum, the electric field amplitude at different points on the cross section are in different phases - although it is my understanding they are usually all in the same polarization.
The concept of phase modes has been known for quite a while.
In the mid-thirties, Henri Chireix published [1] and patented [2] the application of phase
modes in antenna arrays. Since then, the concept has been widely used in
connection with circular arrays (e.g. [3]), multi-arm spiral antennas (e.g. [4]), radio
navigation systems (e.g. [5]), etc. The literature within the area is substantial, with
many papers published in various journals and conference proceedings.
Prior art search is an extinct art, indeed...
[1] H. Chireix, L'Onde Électrique, Vol. 15, pp. 440-456, 1936.
[2] H. Chireix, US Patent No. 2109835, Priority date 7 Jan. 1935, Granted 1 March 1938.
[3] H.L. Knudsen, IRE Trans. Antennas Propagat., Vol. AP-4, No.3, pp. 452-472, July 1956.
[4] J.E. Webb, US Patent No. 3344425, Priority date 13 June 1966, Granted 26 Sept. 1967.
[5] G. Höfgen, US Patent No. 4197542, Priority date 6 April 1977, Granted 8 April 1980.
[6] J.R.F. Guy and D.E.N. Davies, IEE Proc., Vol. 130, Pt. H, No.6, pp. 410-414, Oct. 1983.