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The scattering of radio waves by tall buildings could help engineers triple
the number of channels available to mobile phones. Electromagnetic waves vibrate
in three dimensions—but vibrations in the wave’s direction of travel are
lost by receivers. Mike Andrews at Bell Labs in New Jersey found, however, that
when a radio wave bounces off an object, those vibrations are restored, because
the wave has changed direction. To exploit this effect, Andrews built a 3D
transmitting and a 3D receiving aerial, each with three perpendicularly
polarised antenna (Nature, vol 409, p 316). This arrangement let him
send three times…