Allen,
the main problem you will have is not whether to use signal generator or a
comb generator, but the difference in the radiation characteristic of your
source for correlation and the DUTs that you will later put in the chamber.
You will measure a lots of near-field in you 3m or smaller chamber. The
field pattern at 10 m will be very different. Correlation from near-field to
far-field obtained with source of one (near-field) radiation characteristics
can not be used to predict 10 m radiation of a source with very different
(near-field) radiation characteristics.
To answer your question directly first, the best would be if you could use a
network analyzer or a spectrum analyzer with a tracking generator, so that
you can do swept measurement. However, the way you generate your test field
will make huge difference to the test results. If you use a certain transmit
antenna for your test (correlation), you will get the correlation for that
antenna, but not for a DUT that you might want to test (and use the
correlation) later.
I suggest you take your typical product, physically configure it as in your
typical test setup, it may but does not have be powered. Then couple your
signal source (whatever you choose to use) to the DUT PCB and wiring (here
you have to be a little creative) and do the measurement. Then you can
repeat the same at 10 m site. By doing that you will be ale to get
correlation for that particular kind of DUT. However, if you obtain your
correlation with a DSL modem (e.g. a small box with one power, one DSL, and
one UTP cable) on a wooden 80 cm high turntable, you can not use it to
predict 10 m radiation of a rack-mount multi-port Ethernet switch or any
other DUT that is physically much different.
If you do it like that, and run your test a few times, you will soon gain
experience (some will be from the obtain correlation and some will be your
developed feeling) that you can use to correlate your product measured in
your precompliance chamber to 10 m. I suggest you plot your predicted data
(obtained from the correlation measurement) versus measured over each other
every time you do it (at least for the first 5-10 tests), and it will show
you the spread (uncertainty) of your correlation.
Hope this will help you,
Neven
----- Original Message -----
From: Tudor, Allen <allen_tu...@adc.com>
To: EMC-PCST (E-mail) <emc-p...@majordomo.ieee.org>
Sent: Thursday, January 11, 2001 5:58 AM
Subject: Site Correlation
>
> Greetings:
>
> What's the best way to correlate a pre-compliance chamber (smaller than a
3m
> chamber) to a 10m anechoic chamber? Should I use a signal generator and
> antenna or should I use a comb generator?
>
> Would the answer be different if I were correlating the pre-compliance
> chamber to an OATS?
>
> Thanks in advance.
>
>
> Allen Tudor, Compliance Engineer
> ADC DSL Systems Inc.
> 6531 Meridien Dr.
> Raleigh, NC 27616
> phone: 919.875.3382
> email: allen_tu...@adc.com
>
>
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