Q-Track: In this special zone [near field], the emanations from a radio antenna are rather peculiar. The electric and magnetic fields do not rise and fall in lockstep, for example, as is normally the case with radio waves. And the difference in their timing (their relative phase) is, conveniently enough, a function of the distance from the transmitting antenna.

DecaWave: If power levels are kept low enough, ultrawideband transmissions, being so thinly spread out in frequency, can share the airwaves with conventional radio services without causing interference. Those services have long had to cope with the incidental energy given off by electric motors, automobile ignition systems, and all sorts of digital gadgets that aren’t intended to transmit radio waves. Low-power ultrawideband transmissions are no more menacing, which is why radio authorities around the world are now embracing this technology.

via New Indoor Navigation Technologies Work Where GPS Can’t – IEEE Spectrum.