A concentrated, collimated beam doesn't act like a point source. There's of course some amount of scattering and absorption loss due to atmospheric particles, but other than that a fully collimated wireless energy transmission doesn't lose intensity over distance. Kind of obvious, really, because "where would the energy go?".
Pyrodexter
joined 1 day ago
Quickly glancing through the paper it doesn't really seem to support your claim. They attribute their major losses to the parabolic reflector (meaning they don't have very well concentrated microwave beams?), and say that developing higher efficiency focusing components is important work for the future. I'm kind of guessing that's one thing the Chinese are doing.
Still, I'm sure there are relevant losses even in properly focused microwave beams. How much that is, I have no clue, and didn't see it addressed in the paper. Might have missed it - it was a very quick glance. :)