http://www.ieee-pses.org/symposium http://www.emc2004.org/
--------------------------------------------------
All,
Once again let me thank everyone for their insight. The actual issue was with
our Radiated Emissions Correlation Data. As many of you already know
accreditation is required to perform EMC Testing in North Am erica by A2LA.
Part of the process is A2LA coming in and auditing the technical and quality
side of things as well as all of your set-ups.
For larger tests like Radiated Immunity, BCI, Radiated Emissions etc. each of
the Big Three (Ford, GM, and DCX) handle a correlation to be done. In this
case Ford Motor Company handles the Radiated Emissions Corre lation.
After we went our data the comment coming back was the results showing the
pre-amp was saturated in the 1-100MHz range which spawned me to ask the
question.
We performed several quick tests but the data was correlating anyway, I was
only being extra cautious.
I figured I'd ask all the EMC Gurus here on the list for their opinion and
advice.
In that I thank you all for the feedback.
Rob Kado
EMC Engineer
VWS - Auburn Hills, USA
Tel: 248-340-3828 / Fax: 248-340-3316
Internal Location 3M2
[email protected]
08/12/2004 10:40 AM
To: <[email protected]>, <[email protected]>
cc:
Subject: RE: Pre-amp overload
Rob,
your test tests the preamp for compression. There is more to it than this.
There is mixing going on in any amplifier. The third order products are
usually the issue. For example: 1000 kHz and 1.001 kHz will mix to produce the
third order products of 999 kHz and 1002 kHz. Anyway, the third order products
will increase 3 dB for every 1 dB of increase in signal. So, adding the 10 dB
attenuator will decrease the desired signal by 10 dB and the 3rd order
products by 30 dB. To be safe you might want to use as much attenuation as
possible while maintaining a signal-to-noise ratio of 10 dB or more.
Dave Cuthbert
Micron Technology
From: [email protected]
mailto:[email protected]] On Behalf Of [email protected]
Sent: Thursday, August 05, 2004 9:23 AM
To: [email protected]
Subject: Pre-amp overload
http://www.ieee-pses.org/symposium http://www.emc2004.org/
--------------------------------------------------
EMC Gurus,
We use a pre-amplifier for Radiated Emissions measurements going back to the
spectrum analyzer.
I wonder if anyone has a good standard method to verify that the pre-amp is
not being overloaded?
My thoughts are to use a 10dB, 50W in-line attenuator. To first take a
measurement without and then with the attenuator in-line. I would then
conclude the following:
If the measurement stays the same we have an overload
If the measurement drops by 10dB we are fine
If the measurement drops by more than 10dB I assume we have an overload at
other frequencies that need to be checked.
Does this process sound good to everyone? (pulling out the old college day
experiments here)
Rob Kado
EMC Engineer
VWS - Auburn Hills, USA
Tel: 248-340-3828 / Fax: 248-340-3316
Internal Location 3M2 -------------------------------------------
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This message is from the IEEE Product Safety Engineering Society emc-pstc
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