[SI-LIST] Re: S-parameter passivity... Interpreting the results.

  • From: <Aubrey_Sparkman@xxxxxxxx>
  • To: <travissellis@xxxxxxxxx>, <jhill@xxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
  • Date: Tue, 13 Jun 2006 11:28:24 -0500

John,
Perhaps this is too basic, but did you collect your data with Linear or
Log sweep?  I've seem problems trying to use wide bandwidth data that
was collected without sufficient granularity (to reduce the data set
size).

Aubrey Sparkman=20
Enterprise Engineering Signal Integrity Team
Dell, Inc.=20
Aubrey_Sparkman@xxxxxxxx=20
(512) 723-3592

The Greatest Pleasure in Life is Doing what People say can't be done...

-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of travis ellis
Sent: Tuesday, June 13, 2006 11:19 AM
To: Hill, John; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: S-parameter passivity... Interpreting the
results.

I'm using the 8052D broadband economy calibration kit. I've performed a
full 2port SOLT calibration calibrating out the cabling. All of which
use 3.5mm connectors. Then I attach port 2 to a 3.5mm - GPPO connector
that attaches to a 0.085 gppo terminated cable on one end. The other
end of the cable (DUT) has a coaxial probe. Port 1 is attached to an
sma to gpo connector that is mounted in a brass block and ground
smooth. This provides a coaxial structure that I make contact to with
the coaxial probe that is on the other end of the dut.
 =20
  Travis
"Hill, John" <jhill@xxxxxxxxxx> wrote:  Travis,

Which Calibration kit are you using and can you describe what is between
the calibration plane and the thing you are trying to model? BTW, what
RF connector are you using?

Best regards,

John


=20

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-----Original Message-----

From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of travis ellis
Sent: Tuesday, June 13, 2006 11:00 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] S-parameter passivity... Interpreting the results.

I've been taking measurements with a VNA then running them through a
passivity checker. The basis for the code was originally posted by Ray.
I've modified it to meet my needs. Added plotting capabilities, log mag
format handling, and nudging of the non-passive values when only a few
points are out of spec etc. I don't think I broke anything in the
process but what I've noticed is that the eigen values of some of my
measurements are very noisy. The better measurements oscillate too but
they trend upward with increasing frequency. The suspect measurements
oscillate between near 0 and approximately 0.4 from point to point
across the higher frequency bands. The magnitude of the s-parameters
seem to be noisy as well. I've gone through my setup to make sure that
my cables don't have loose/bad connections. Replaced some connectors
that seemed inadequate and while things got marginally better the
measurements still contained noise. The noise source seems to be my
fixturing. Unfortunately I don't think I can improve this given my time
constraints.=20
   =20
    The only thing that I've noticed is that the time domain simulations
take longer than those created with a data set that isn't as noisy.
   =20
   =20
    Is there a way to decide if these models are accurate enough to be
reliable?
   =20
    Regards,
   =20
    Travis
 =20
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