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[Ham-80211] "Commodity Class Phased Array Antennas" for HSMM?

David Young dyoung at pobox.com
Sun Aug 1 23:57:17 UTC 2004

On Sun, Aug 01, 2004 at 05:49:12PM -0500, Gerry Creager N5JXS wrote:
> Since I couldn't see the images in the PPT (didn't get them, or 
> OpenOffice didn't like 'em, don't know which) I couldn't completely 
> evaluate the idea.

I have put a paper about the idea at
<http://che.ojctech.com/~dyoung/public/kajiya-antenna.pdf>.  The video
at Microsoft is pretty good.


> If you're physically steering these things, I'm really confused.  I 
> think it'd be useful, though.
> >I am confident, as a "software guy," that the software problems are
> >tractable.  The hardware problems look pretty tough to me.  A software
> >feedback loop based on received signal strength could "train" the beam
> >onto the station that you want to talk to by moving the voice coil.
> The hardware part is tedious and potentially expensive because of 
> element yield, but not particularly hard.
> >Regarding fabrication, my thinking is that you would download an "open
> >source" PCB design from the web and send it for manufacture.  (Although,
> >there are electrical engineers who make PCBs at home.)  You can buy a
> >6"x6" piece of alumina for less than $20 on-line.  I figure machining that
> >will be a pain, but it is nothing a determined HSMM hobbyist could not do.
> It may be beyond my machining capabilities:=)
> >BTW, the steering is horizontal only, although Kajiya tells how you could
> >do vertical tilt.  Horizontal steering is perfectly adequate for a lot of
> >applications.  For example, my main interest is in mitigating 2.4GHz
> >band interference while keeping a "mesh" neighborhood network connected.
> >You can steer the beam away from most interference with a horizontal 
> >rotation.
> Likely, with a little programming, you can train the system to steer 
> toward the peak of the desired signal, or use the hueristics to optimize 
> the desired and interfering signals...
> >Kajiya proposed to build a 4-sector system with one of these antennas
> >in each sector, but that requires RF switches.  A 2-sector system might
> >just work, and no RF switches are necessary if you re-use the antenna
> >diversity switch.
> PIN diodes don't work too well at these frequencies, but switches are 
> do-able.
> I'll try to find a working, non-infected Windows system this week and 
> look at the site again, and try to understand his thoughts.  If there'd 
> been an e-mail add for him, I'd have already e-mailed Kajiya for some 
> more detail...
> Gerry
> -- 
> Gerry Creager -- gerry.creager at tamu.edu
> Network Engineering -- AATLT, Texas A&M University	
> Cell: 979.229.5301 Office: 979.458.4020 FAX: 979.847.8578
> Page: 979.228.0173
> Office: 903A Eller Bldg, TAMU, College Station, TX 77843
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David Young             OJC Technologies
dyoung at ojctech.com      Urbana, IL * (217) 278-3933

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