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:Two questions (Score:3, Insightful)
Re:in this house we obey shannon's theorem (Score:5, Insightful)
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.
NOT 140 years late (Score:4, Insightful)
See http://www.physics.gla.ac.uk/Optics/play/photonOAM/ [gla.ac.uk]
Re:Two questions (Score:2, Insightful)
if you look at it like that, we'll never be able to disprove the paranormal since we'll never be able to claim that we've found all possible ways to receive and interpret data. it's one of the reasons why i think it's silly to even try disproving such things.
Does not violate shannons theorm. (Score:3, Insightful)
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~
Twisted Beams = Phase Modes = Old Stuff (Score:2, Insightful)
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.