robot for wireless channel measurement

Hi,
I'd like to do some automated wireless channel measurements in my lab at 2.4 GHz, by covering a grid at 5 cm intervals. Placing the antenna
by hand takes too long for the size of the grid I'm using -- I'd like to at least be able to automatically cover one row, if not the entire grid, by attaching my antenna to an inexpensive programmable robot with a fairly precise step motor on the wheels. Would anyone have any recommendations on something that would work -- I've already tried the Lego Mindstorm, but the positioning accuracy isn't quite good enough for what I'm after.
Thanks a lot, John M.
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jhnmstrn wrote:

The Garcia robot from Acroname was developed to have very accurate position encoding.
http://acroname.com/garcia/garcia.html
- dan michaels www.oricomtech.com ==================
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I thought about that too. I envisioned a robot with a receiver connected to an LED that indicated RX quality using intensity or color. Mount a stationary video camera that has a full view of your operating area and take a movie of the robot scanning the room (or in my case a football field). Then use some software to essentially time-lapse all the video into one image so you can get a map of where all the receiver drop outs are.
This method does not require an accurate positioning system since the robot just has to more or less randomly cover your measurement area. - I suppose you could run around the room with the reciever in your hand instead of using a robot, but then this post would be off topic.
-howy

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Hi John,
at work we did something similar. Initially we planned to use an XY-plotter on which we would mount the antenna with a suitable non-metal pole, which I still think would have been a good idea. However, once our mechanical service department got hold of this task, it ended up being a custom-built set-up of about 60"x60" built from 4"x4" metal beams and stepper motors with an accuracy of 100um and strong enough to pull off your fingers if they happened to get caught in the mechanism. They even built a custom cart to transport it! Oh well, that's part of the joy of working for a large multinational company ;-)
This set-up and the measurements that we did with it are described in the PhD thesis of one of my colleagues, Lukas Leyten. You can download his thesis at:
http://alexandria.tue.nl/extra2/200112987.pdf
and there's a drawing of the set-up on page 98.
The set-up was also used by another colleague, Guido Dolmans, who also refers to it in his PhD thesis:
http://alexandria.tue.nl/extra2/9703559.pdf
In fact, this thesis contains a picture on page 170.
Even though the custom-built set-up worked great, I would recommend you look into the first idea (a larger digital XY plotter) first, unless you also happen to work for a multi-national as well ;-)
Good luck with your measurements!
Best regards,
Peter
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