[SI-LIST] Re: De-embed fixture
- From: "Al Neves" <al@xxxxxxxxxxxxxxxxx>
- To: "'Jim Nadolny'" <jim.nadolny@xxxxxxxxxx>, "'Ming Li'" <swagguy09@xxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Fri, 5 Aug 2011 08:17:05 -0700
Unfortunately, most of the existing de-embedding approaches are eigenvalue
solution based, and can become ill conditioned with measurement noise,
mediocre return loss due to poor fixture design, or measurements. The noise
impact can be clearly seen when you make VNA measurements with high IF
filter bandwidth, and then attempt de-embedding. Use a lot of averaging,
low IF filter of 500Hz, and design a fixture with good return loss
represents a good start. Pristine and repeatable launches are a must.
Aside: Anyone have data on Automatic Fixture Removal used in Agilent PLTS?
The Agilent folks discussed this in a tutorial in DesignCon 2011 and used
our 15G Channel Modeling, CMP-08 but haven't seen a definitive test suite
showing 3D EM correspondence, measurement, and overall validation.
We are probably going to do one of our webinairs on 4-port de-embedding
within the next few months. BTW, feel free to ping us for our existing
Webinair, www.youtube.com/watch?v=vUB77mAVWXQ. We got really good feedback
on this webinair, and it isn't riddled with shameless marketing.
Products for the Signal Integrity Practitioner
Wild River Technology LLC
Alfred P. Neves
Founder - Engineer - Business Development
(503) 718 7172 Office
(503) 679 2429 Mobile
735 South East 16th Ave.
Hillsboro, OR 97123
www.wildrivertech.com
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Jim Nadolny
Sent: Thursday, August 04, 2011 9:40 AM
To: Ming Li; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: De-embed fixture
Ming Li,
I worked with Agilent on this exact problem.
Agilent developed a method within ADS to perform "S-parameter bi-section".
The method is pretty cool, you iterate in frequency to develop 2 mirror
images which when combined yield the fixture response. It worked perfectly
on simulated data but had a lot of glitches when using real world data.
Small things like phase wrap and noise lead to problems with the data. The
big killer is that you assume the fixture response is symmetric, but in in
all likelihood it's not perfectly symmetric.
To Agilent's credit, we did get there with this method but at the end of the
day a TRL/M cal method was more robust and quicker for fixture removal.
Good luck -
jn
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Ming Li
Sent: Thursday, August 04, 2011 12:02 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] De-embed fixture
Hi, experts,
I get two identical fixtures on both sides of my DUT. And I got the s4p data
of the fixture itself and s4p data of the DUT cascading with the two
fixtures. Could you please kindly let me know how I can de-embed the fixture
and get the s4p data for the DUT? I know the math behind it but the data
itself is too big to calculate.
Thanks in advance.
Regards,
Ming Li
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