60 GHz Technology

[James Wolf]

60 GHz is used in space where the earth's atmosphere does not exist.  But it
also provides LPI and LPD as it will never make it down through the
atmosphere.
The sweet spot for mm waves seems to be in the 74-80 GHz range. With 100 mw
and a two ft dish on each end, you can get about three miles.  As I recall,
the 3 dB beamwidth from a two ft dish is around 4 degrees.  As you can
imagine, the Fresnel zone is small too.  There are quite a few of these
being used for high speed data throughput.  Businesses who want
uninterrupted low latency high speed data from one building to another use
them - High Frequency market traders use them that way. 
Early radios were just On-Off keying at 1 Gb/s.  Later units are at 3 Gb/s
BPSK with 10 G's on the lab benches. 10 watt power amp prototypes are
floating around too but as far as I know, that's not commercial stuff.  I
have not seen any QPSK so far.

Jim, KR9U


-----Original Message-----
From: tacos-bounces+jbwolf=comcast.net at amrad.org
[mailto:tacos-bounces+jbwolf=comcast.net at amrad.org] On Behalf Of Robert E.
Seastrom
Sent: Thursday, July 05, 2012 4:57 PM
To: andre.kesteloot at ieee.org
Cc: Tacos
Subject: Re: 60 GHz Technology


Quoting the article:

   Attenuation is also aggravated by H2O absorption. Water (mainly oxygen
   molecules) in the atmosphere absorbs radio waves since the signal
   wavelength is about the size of the oxygen molecules. This absorption
   effect peaks at 60 GHz, making this a real issue for longer-range
   applications.

60 GHz = 5mm wavelength.  Them's some mighty big oxygen molecules.  :-)

-r

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