Posted by
K7TV on
May 04, 2012; 5:10am
URL: http://elecraft.85.s1.nabble.com/OT-Distinguishable-angular-momentum-in-radio-photons-tp7525974.html
The May 2012 issue of the IEEE Spectrum magazine reports that researchers in
Italy and Sweden were able to conduct two separate instances of radio
communication on the exact same frequency, without increasing bandwidth, and
without time-division multiplexing, be making the transmissions differ in
angular momentum. One transmission used linear polarization, and the other
was given angular momentum by means of a dish with a radial cut, where the
metal was bent backwards/forwards on the two sides of the cut. Apparently
this is not just a case of linear vs circular polarization, as circular
polarization can be readily picked up by a linearly polarized antenna, and
apparently the two channels did not interfere with each other. The
researchers claim that this demonstration points to the possibility that the
radio photons can be given multiple, quanized levels of angular momentum,
making possible several more communication channels without increased
bandwidth. Other researchers say that this is just a form of MIMO. Wikipedia
describes MIMO as the technique of using multiple antennas as in diversity
reception or in gain increases obtained by phasing the antennas.
My apologies if this is too far OT.
73,
Erik K7TV
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