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Rectangular PatcHow to measure, or know whether or not a printed
antenna - RF Cafe Forums
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| jinhao
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Post subject: How to measure, or know whether or not a printed antenna
Posted: Wed Apr 25, 2007 12:03 pm
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| Lieutenant |
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Joined: Tue Apr 24, 2007
1:10 pm
Posts: 2 |
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is well / poor matched? since a printed antenna
is part of the circuit board, it seems that we are
not capable to measure VSWR.
This is a big problem
for me.
Thank you very much.
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nubbage |
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Post subject:
Posted: Thu Apr 26, 2007 3:14 am
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| General |
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Joined: Fri Feb 17, 2006
12:07 pm
Posts: 218
Location: London UK
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Do not despair, there may be a solution to this.
If you have access to the length of strip-line feeding
the antenna element, it may be possible to fabricate
a small directional sensor. This comprises a lambda/4
length of microstrip with a schottky diode at one
end and a 100 ohm chip resistor at the other end,
connected to ground. The diode has a bypass chip
capacitor to ground on the dc side of the diode.
With the diode oriented towards the antenna end
the rectified energy is mostly due to, and proportional
to, forward power. Reversing the orientation results
in picking up and rectifying mainly power reflected
back from the antenna. The ratio of the 2 readings
is a very approximate measure of the VSWR.
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rftroubleshooter |
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Post subject:
Posted: Wed May 16, 2007 4:32 pm
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Joined: Wed May 16, 2007
4:16 pm
Posts: 5 |
If it were me, I'd spend the $1500 and rent a vector
network analyzer. It will allow you to visualize
what is going on with the impedence; you get a picture
of the complex impedence, not just the VSWR.
This post has a brief method you could use to
measure your PCB antenna using a VNA:
- Steve Montgomery The RF Troubleshooter
www.rftroubleshooter.com |
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Posted 11/12/2012
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