[lutusp]

> The more antennas the fewer spots with unwanted constructive interference.

Yes, true, but the entire system becomes more complex for a small improvement in performance. Also, most of the theoretical work in a scheme like this would focus on the least common denominator, which is three antennas.

Interestingly, for a roughly circular array of antennas, you end up with concentric rings of high signal strength as you approach the midpoint of the array. So even the thesis that you've eliminated unused hot spots breaks down in some cases.

Here's my diagram for three phase-controlled antennas (the blue dots):

http://i.imgur.com/tyyVh0j.png

The wavelengths in this diagram are longer than for a cell system, it's just to show how this idea works. Buy adjusting the phase at each antenna, you can move the high-strength lobes around to match up with the location of a given device.