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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
I would have had first post, but my waves got twisted...
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.
It's not obvious to me what all the excitement is about.
"Huge" amounts of data as compared to what exactly ?
Whatever they are doing, it can't get past Shannon's theorem as a limit on the amount of information available for a given bandwidth.
This looks to me like it probably simply reduces to MIMO :
http://en.wikipedia.org/wiki/Multiple-input_multiple-output
Either way the capacity is limited to N * the capacity for one antenna (remember Shannon's law applies per channel).
So back to, what does this do exactly ?
Absolute statements are never true
Don't cross the streams.
After implementing this all radio communications play Chubby Checker's "The Twist" softly in the background.
TM?
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.
Really? No wai! That's like totally so not Apple y'know. Back when Steve was still around they would've ... like ... never done that.
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
When I read the summary, for some reason I immediately thought of the dearly departed Roland Piquepaille. It's a cool-sounding idea, easy to convert from "science" to "media", and utterly impractical for the putative use. The research was done with a military antenna array so massive that people were afraid it would destroy the ionosphere, so there's no chance of seeing a new band on your car radio (and an excellent chance that it will never be more than a scientific curiosity). But "Twisted Radio Beams" -- that's a headline that the public can sink their teeth into.
So I immediately thought of Roland, and realized just how much I miss his gee-whiz almost-scientific submissions. I'm going to tag this article "ohnoitsroland" (and my own invention, "pigpile") in his honor.
Stressed? Me? Of course not. Stress is what a rubber band feels before it breaks, silly.
DCODER?
no
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
Yes, yes, oh my God yes!
Mother, do you think they'll like this sig?
Twisted radio == good.
Twisted schwartz == bad.
Is spinning radio waves anything like spinning bullets? Because that would be totally awesome.
Mod my comments down. It'll be fun.
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.
Wikipedia has a reasonably easy-to-follow explanation of how this works.
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)
Carl Segan wants his idea back from "Contact"
I thought this has already been used? GPS sats shower down circular polarized signals. The antennas even have a "twist"-shaped like conductor.
This is not about technology. With new encoding schemes and whatnot, there is enough space to accomodate most uses. The problem is one of economics. First, entrenched infrastructure. It costs money to upgrade, as this whole "digital TV" transition proves (arguments about corruption aside). Also, in this country at least airwaves are sold off to the highest bidder, not necessarily the "Best interest" use of that spectrum. So we have technology from the 1940s working side-by-side with stuff that became out of date 3 years ago. The problem isn't spectrum allocation or encoding, or any fancy tech crap.
It's economics. And economics is about people. And the people in control of the airwaves are making a huge mess of things because they believe that highest bidder = most public good. You want to "untangle" the airwaves? You need to start by firing everyone on the board of the FCC, restructuring it, and then preparing to sink at least a hundred billion into retooling the infrastructure. Since nobody wants to do that... Get used to congestion, crap reception, and paying through the nose for basic services. Like your cell phone.
#fuckbeta #iamslashdot #dicemustdie
I'm thinking he might be related to this Shampoo guy.
Hi,
Adding the additional orthogonal dimensionality of RHCP and LHCP polarization to the extensively used I and Q complex amplitude channels of conventional modulation yields a baseline 50% increase in bits/sec/hz at a given SNR vs BER (which is the appropriate metric when discussing modulation format efficiency). Prototypes backed up by rigorous derivation exist that prove the effect, and Direct Spatial Antenna Modulation (DSAM) is one of the most efficient means to implement this functionality on the emerging technology horizon.
Basically, a dimensionality of one gives you 1 bit/sec/hz at given BER vs SNR (two states). Two gives you 2 bits/sec/hz at same BER vs SNR (four states) and then you are out of complex amplitude signal dimensions. Polarization adds a third dimension, yielding a new optimum at 3 bits/sec/hz at same SNR. Conventional modulation currently gets at higher bits/sec/hz through slicing up the two I and Q channel sets more thinly, requiring more SNR to get the same BER - so requires more transmit power for same link range. This is why your WLAN throttles back to BPSK (1bit/sec/hz) from 16-QAM (4bits/sec/hz) when the going gets rough.
Really, the innovation is in the treatment of polarization as a dimension on par with the I and Q channels so heavily treated in conventional modulation theory. Thus my involvement in this area of research...
Cheers!
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
What exactly do they mean by "twist". Do they mean to transmit information by modulating the polarity of the signal?
do they have a better tinfoil hat for me?
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.
AM, FM, and TM?
Great, I predict this will file for chapter 11 shortly, along with that XM crap.
The news refers to the use of angular momentum of light (radio waves in this case), not to the spin (polarization). Apart from polarization, light can have an angular momentum, which consists in a torque-like space distribution of its phase. Since this refers to a continuous variable, this application extends the set AM+FM to AM+FM+LM or whatever they call this new modulation.
The angular momentum of light is years old, but the news is that it has been recently implemented in the radio wavelength, which apparently was difficult.
You mean Shamwow?
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
What you say is inmpossible [sic]
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.
TUBULAR communications... I wonder if they will use real wires to guide the signal. A WHOLE new infrastructure project can be charge up...
Imagine the rat's nest of horrors to emerge from that... Our voices will sound like we emerged from my chamber of IT horrors... All together now:
skweee skweee squeee squeee
The new headquarters can be based at... "SHOCKCOM": Somnambulizing High Output Communications-Killing Civilians On Mass...
(Damn, dropped my crack bowl...)
Previously: "Linux... Toward the Sunrise..." Now: "Linux... Toward the-- No, now, part of Every Sunrise"
The problem with a circularly polarized signal is that it is not orthogonal to any linearly polarized one. In other words, while two linearly cross-polarized signals won't interfere with one another, any linearly polarized signal will interfere with all circularly polarized ones. So, this technique won't help to avoid interference on the airwaves.
I don't actually believe that photons can have angular momentum. photons carry +/-1 angular momentum. You can't excite an atom to a j+2 state with a single photon.
light fields can induce a torque on macroscopic object but this is through the accumulation of single photon absorptions delivering then J+1 angular momentum.
As near as I can tell all instances of so-called orbital angular momentum are just structured light fields. this one is no exception.
You can deliver info via the structured light field but only if the antenna is larger than the size of the structured light field spatial modulation width.
Okay tell me why I'm wrong.
Some drink at the fountain of knowledge. Others just gargle.
Yes, but can it get us to alternate universes?
(For the humorless, the novel "Twistor" describes an effect sort of like this and is a damned good "hard" science fiction book.)
Learning HOW to think is more important than learning WHAT to think.
From Vernor Vinge's "Fire Upon the Deep":
"There are simple tricks that are almost never noticed till a very high technology is attained. For instance, quantum torsion antennas can be built from silver and cobalt steel arrays, if the geometry is correct. Unfortunately, finding the proper geometry involves lots of theory and the ability to solve some large partial differential equations. There are many Slow Zoners who never discover the principles."
Don't suppose anyone else thought of this passage, which takes place when Pham's team is trying to jump-start the low-tech Tine civilization?
Maybe it was BOTH "Kill the family" and "Bill loves Emily" - and the message's quantum supposition function collapsed under observation to actually be "Bill is Emily" (and Bill's cat, being so hurt at her owner being exposed publicly as a freak, went into a box and fired the gun)
I still think that Twisted Sister was a good hair band, at least in relation to most other hair bands.
I'm curious whether the channel capacity gained here would be equivalent to the channel capacity gained by using the antennas as an in-phase array and beam forming towards the receiver.
I'm guessing that it would be.
Well, as of late, I'm inclined to believe John Galt is a troll.
Are already trying to prevent this new technology. They say it causes interference and are hoping to ban any upstarts from using it to compete against them.
The US government also hates it because it cuts into revenue stream which they charge out the ass.
...as long as you dont cross them.
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.
Wasn't this very idea used in the book Contact by Carl Sagan. The aliens sent their message in three parts. They used Amplitude, Frequency, and Polarization.
Could we send angular momentum-modulated photons down a fiber? Seems like a nice, controlled channel which would work even better than radio waves. Get ready for DWAMDM (Dense Wavelength + Angular Momentum Division Multiplexing) multi-terabit fiber to the home! Woot!
I find this concept really interesting and confusing at the same time. Consider that within plasma laboratories, we can observe certain fundamental morphologies that naturally result from the existence of charge density. Plasmas naturally form double layers, which tend to protect a plasma's charge. The double layer leads to the formation of plasma filaments. We see within the laboratory that plasma filaments tend to exhibit long-range attraction and short-range repulsion with one another. This causes the filaments to twist around one another like a braided rope. Within the plasma laboratory, we observe these complex twisted transfer charged particles very efficiently. They are called Birkeland Currents.
We see these braided filament plasma structures in space too, like in the Cygnus Loop ...
http://www.spacetelescope.org/videos/hd1080p_screen/heic0712g.mp4
http://www.thunderbolts.info/tpod/2007/arch07/070103cygnusloop.htm
Braided ropelike plasma structures are the fingerprints of electromagnetic activity. When you see plasma behaving this way, you need to make sure that you're not trying to use fluids-based equations to understand/model it.
It's interesting that the same thing can be done with respect to radio waves. I'm actually a little bit confused as to why this works for radio waves. When Birkeland Currents do this, they require the existence of a plasma medium, and the structures do their thing in the lab because of the existence of the ionization. The plasma both responds to magnetic fields and creates its own due to the right-hand rule. But these guys seem to be saying that they can create these structures within the Earth's atmosphere in the absence of a plasma medium (?). With Birkeland Currents, the collimation occurs because the flow of charged particles generates a magnetic field.
I'm not getting something. Any plasma physicists out there??? Is HAARP creating an ionized pathway for the signal through the atmosphere?
"A man cannot begin to learn that which he thinks he already knows." --Epictetus, 1st Century A.D.
Has anyone told the people at CETI about this? Sound like it could be the reason we never hear anything....