This is amazing — or not really if you think about it — Orbital Angular Momentum Multiplexing (OAMM) for radio waves. Now how well does it penetrate buildings, how much power does it take, and can it really work over long distances? Could it become of the equivalent of Dense Wave Division Multiplexing (DWDM ) for radio spectrum communication?
Willner and others have previously demonstrated the twisting technique with beams of light reaching data transmission speeds of 2.56 terabits per second in 2012 and 1.6 terabits per second over optical fiber in 2013. Demonstrating the technique using another band of the electromagnetic spectrum, though, helps to drive home its viability across a variety of waves.
Putting these principles to work in radio waves, Willner and his team used four antennas to send polarization-multiplexed beams, resulting in a total of eight channels of data. Those beams of data were sent through specially shaped “spiral phase plates,” Teflon plates that don’t absorb the beams, but do change their shape, twisting them slightly. The twisted waves are then gathered by a multiplexer and sent through a single transmitter aperture. Since each wave has a slightly different orbital angular momentum, they can travel along a shared axis without interfering with one another, similar to how several subway riders can steady themselves around a single pole by holding it at different points.
The combined beam, which takes on a helical shape like, travels through another aperture at the receiver, after which it is split back into four beams by a demultiplexer. The four beams then pass through another set of spiral phase plates. These plates are inverted versions of the first set, which undo the initial twisting and prepare the waves to deliver their data payload.
More: ‘Twisted’ Radio Beams Data at 32 Gigabits Per Second - IEEE Spectrum