Twisted Radio Beams Could Untangle the Airwaves 183
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."
Re:damn (Score:5, Informative)
The article suggests the technique only works really for point-to-point transmission. Regular amplitude/phase modulation (QAM) is still the best generally I'd imagine.
No (Score:3, Informative)
Re:Two questions (Score:2, Informative)
1. Its completely practical considering the first ever case of these types of waves ever being sent was just published and the first ever example was done on a 48 antenna space array, not to mention they don't have a receiver. Given that most technology moves immediately from research to mass production in the space of a week, I'd say $20-30.
2. Again, seeing as the first ever examples of this were just transmitted with no receiver there's been a lot of time for field study. Or are you saying you're one of the unlucky few /. readers who don't have a home built twisted radio frequency array?!?! I built one and I didn't even RTFA! So first step is to get one working, and then I'll beam the answer to you at twist frequency 124.
Actually, all kidding aside the answer is that this technology is brand new. Its also completely worthless because there isn't an immediate practical application available in the store. Stupid scientists!
FM is polarized as it is for a reason (Score:3, Informative)
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.
Twisted Radio Waves (Score:3, Informative)
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.
Not New, Not News (Score:2, Informative)
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.
Re:damn (Score:5, Informative)
You are aware that digital radio techniques all use amplitude, frequency or phase modulation, right? The difference is that the modulation is digital (or thereabouts) rather than analog.
Re:Twisty Modulation? (Score:2, Informative)
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
Carl Segan wants his idea back from "Contact" (Score:1, Informative)
Carl Segan wants his idea back from "Contact"
It's not about polarization (Score:5, Informative)
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/ [gla.ac.uk]
Re:No (Score:5, Informative)
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/ [gla.ac.uk]
Incorrect (Score:4, Informative)
See http://www.physics.gla.ac.uk/Optics/play/photonOAM/ [gla.ac.uk]
This NOT already done (Score:5, Informative)
They're using physics that wasn't even discovered until 1992.
See http://www.physics.gla.ac.uk/Optics/play/photonOAM/ [gla.ac.uk]
Re:damn (Score:4, Informative)
Re:damn (Score:4, Informative)
Check out the wikipedia page for OFDM: http://en.wikipedia.org/wiki/OFDM [wikipedia.org]
First paragraph: "Each sub-carrier is modulated with a conventional modulation scheme (such as quadrature amplitude modulation or phase shift keying)."
You're right, analog transmissions are generally less efficient for transmitting data. Your AM radio vs. digital radio example isn't quite fair, since the digital radio is compressed - that is, it isn't actually transmitting as much information as the analog channel.
Your overall point is flawed. It is not the type of modulation (AM or FM) that is at fault, but rather the analog nature of the transmission. This new technique actually sounds like it would NOT lend itself naturally to analog transmissions - it would be far more likely to be used with digital encoding.
In fact, you could probably use OFDM if you want to, just like it is commonly used with amplitude modulation.
Re:NOT 140 years late (Score:4, Informative)
It won't take but a second for you to stop guessing that it's about polarization once you see their clear explanation that it's different.
Orbital Angular Momentum versus Polarization (Score:4, Informative)
This article [aip.org] 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.