Good day, Gert.
The straightforward answer is an antenna with enough gain to provide the
margin needed for a valid test. Gain required can be reduced by using lower
loss coax and up-front preamplification. Add 8 dB antenna gain, cut cable
loss in half, and add a low-noise preamp with 10 dB gain at the antenna (or
any equivalent combination). i have recently seen that done with good results.
In a "previous life" I brought my 800-1000 MHz noise floor down with a much
better coax cable, but that was for a 10 meter OATS. Then I had to either
switch to the internal preselector or add attenuation because the "usual
8447D" was overloaded by ambients. My supervisor and co-workers were not
comfortable with these measures, which didn't last long, however and that
company no longer exists. But I digress.
More gain, less loss.
Cortland Richmond
KA5S
----- Original Message -----
From: ce-test, qualified testing bv - Gert Gremmen
<mailto:[email protected]>
To: [email protected]
Sent: 5/25/2010 3:17:45 PM
Subject: Radiated emission testing for automotive at low levels.
Colleagues and friends,
I have recently been asked to quote testing for automotive
car manufacturers ESA specifications.
Part of the specification is very low level testing,
as low as 20 dBuv/m at 120 Khz BW above 1 Gig.
Can any of you shine their lights/contribute 2 cents
on the test configuration needed for that.
I have run into the following problem:
Our R&S analyzer has a noise floor at 120 kHz bandwidth
of approximately -71 dBm. Adding a 6 dB preamplifier noise and 24 dB
gain lowers the noise floor to
89 dBm (18 dBuV). Our horn antenna (3115) has a AF of >20 dB (@1m)
and the resulting noise level field strength is about >38 dBuV/m
What is your choice in solving this problem ?
Gert Gremmen
-
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