[SI-LIST] Re: Radiation masking noise measurements

If your noise is uncorrelated to the signals of interest you can use a scope
to measure the noise.  Trigger the scope off the function generator, use a
lot of averaging on the scope and any non-correlated noise should average
out leaving data correlated to the frequency of the function generator.  If
the noise that is interfering with the measurements is correlated then you
have a different problem.  I would check your connections to your test board
from both the generator and the scope.  There should be no or minimal loops
in the connections.  i.e., there should be short wires between the ends of
the coax and the board, short being 0.100" or less.  Also the grounds on the
board that you are referencing to should be near the injection and probing
points respectfully.

Tom Dagostino
Teraspeed Consulting Group LLC     Teraspeed Consulting Group LLC
2926 SE Yamhill St.                Device Modeling Division
Portland, OR 97214                 13610 SW Harness Lane
                                   Beaverton, OR 97008
http://www.teraspeed.com           503-430-1065
tom@xxxxxxxxxxxxx


-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Virendra
Sent: Thursday, May 22, 2003 6:04 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Radiation masking noise measurements


Hi all,
I am trying to measure noise on a small board about 2inch by 2inch with
blind and microvias.  The board does not have an oscillator so we are
exciting it with a function generator.  This arrangement seems to be
radiating a lot and seems to be masking the actual noise on the board.  The
impedance profile of the board around the frequency fed from the function
generator shows a very low impedance and i would not expect to see such a
significant amount of noise at that frequency.
Is there any way around this problem of the noise being masked by the
radiation?

Thanks in advance,

Regards,
Virendra Adsure





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