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Electric Field strength to power conversion.. - RF Cafe Forums
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| bparker
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Post subject: Electric Field strength to power conversion..
Posted: Tue Apr 12, 2005 8:01 am
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Joined: Fri Aug 27, 2004
11:25 am
Posts: 4
Location: Cape Town, R.S.A.
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Hi All,
I was hoping someone could help me
with a fundamental issue.
I have had some
EMC problems (radiated) and am trying to analyse
the results.
The test is done by monitoring
the radiated signal with an antenna placed 1m from
the DUT. The levels are then given in dBuV/m.
I understand that this is a measure of the Electric
field strength, but my question is how to relate
this to an absolute power measurement.
Is it
a straight conversion from dBuV to dBm, assuming
a 50 ohm system, and can the /m part of the unit
be dropped because of the distance between DUT and
antenna being 1m?
If this reasoning was followed,
a +30dBuV/m translates to -77dBm/m, or -7dBm power
level at source if a cable with 70dB isolation was
used. (cable connected to known source of offending
signal and terminated into 50 ohm)
Am I way
off the mark, and if so can someone please shed
some light?
_________________
B.K.P.
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RMYREHN |
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Post subject: Electric Field strength to power conversion..
Posted: Tue May 10, 2005 10:13 am
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To convert from dBuV to dBm in a 50 ohm system,
just subtract 107 from the value in dBuV. As far
as dropping the /m (per meter), you will need to
obtain the antenna correction factor (which should
have been supplied with the antenna) and subtract
it from the value. Once you have this answer, it
is no longer a field strength though. This is useful
if you want to determine what level to inject (bypassing
the antenna) when checking out your measurement
system
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Posted 11/12/2012
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