Department of Energy studied the use of phased arrays to beam power (http://spaceflighthistory.blogspot.com/2016/12/energy-from-space-department-of.html http://

Department of Energy studied the use of phased arrays to beam power (http://spaceflighthistory.blogspot.com/2016/12/energy-from-space-department-of.html http://spaceflighthistory.blogspot.com/2016/12/energy-from-s...). The use of a pilot signal was useful because it prevented any 'death ray' scenarios. The transmitter would only be able to beam power to a receiver, even if it was knocked off target. I am not sure what the benefit of a small receiver would be for power transmission. The DoE system used the same 2.45 GHz frequency as a microwave oven, so the receiver was more like chicken wire than the receivers we are familiar with. They would have been very large to prevent overflying aircraft or birds from being fried by the transmission, and could maybe be placed on pylons over otherwise useful land.