RE: 5G Will Use MIMO and Millimeter Wave Frequencies

gervasi — Thu, 18 Feb 2016 22:44:30 GMT

Dr. Antoine Roederer of Delft University in the Netherlands sent the following comment to me privately. I agree with it, so I'm posting it here.

I believe that in fact the power decays at the same 1/r^2 rate, independent of frequency.
But the surface of the omni receive antenna (lambda^2/4xpi) of Mr Friis is much smaller at millimeter waves and it captures less of the incoming power accordingly.
If you keep the transmit antenna omni directional or with same gain Gt and the receive antenna size constant, then you get the same power transfer at all frequencies.
The books (and some of their authors too) are not clear on this.
https://en.wikipedia.org/wiki/Free-space_path_loss has it right in their physical explanation section…

RE: 5G Will Use MIMO and Millimeter Wave Frequencies

DAB — Mon, 10 Nov 2014 20:17:12 GMT

I am still amazed at the high frequencies we continue to exploit.

I remember when 1 Ghz was a big deal and we had to use waveguides and a lot of RF filters.

Now we have devices running those frequencies with just a board layout for an antenna.

DAB