Quote:
Originally Posted by J.B. Wood
Hello, all. I came across an article in one of my science mags in which
some researchers had discovered a method to coax more bandwidth out of a
given portion of the EM spectrum by "twisting" radio waves together.
Nothing more technical than that in the article. Well, I managed to
find one the author's papers on the subject online:
http://arxiv.org/pdf/1107.2348v2
If this technique is viable, I'm wondering why it is only now being
contemplated. Note the "twisted parabolic antenna" (Fig. 3A) on p.16.
Of course this makes me want to do some experiments in the ham bands.
(I hope this doesn't turn out to be another CFA-like pursuit).
Sincerely, and 73s from N4GGO,
--
J. B. Wood e-mail: |
On reading the paper associated with this claim, it appears that once you wade through the optical and momentum stuff you find that they have set up two transmitters near each other pointed to a common location where they have set up an interferometer. An RF interferometer is two antennas set up with a variable phase adjustment on one leg and both signals fed to a summing junction. Assuming the signal levels are closely matched (reasonable given the similar transmission path geometry), proper phase adjustment causes one of the signals to cancels leaving you with a phase adjusted version of the other signal. Re-adjustment the phase shift causes the other signal to cancel and gives the second signal.
To me this does not signify an new phenomenon it is just a simplified version of MIMO. This is already well understood in the Communications Systems world and is in use in IEEE 802.11N.
This can be technique done with out the fancy split antennas. In fact it has been done many times with simple dipole antennas.
Is this just a case of these physicists finally finding out something that the Communications Engineers have been using for years?
March 3rd 12, 07:31 PM
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