Our Channel Modeling platform used for SERDES testing, ISI-32 is constructed
with FR408HR and the loss dB/inch/GHz as calculated by Simbeor, and ADS is
close to the Isola published loss numbers for loss tangent. This platform
includes multiple microstrip and stripline lengths from approximately 3inches
to 50inches for creating ISI in several inch increments. We have found the
Isola published data to provide reasonably good accuracy for their materials.
Tomâs point is important in that return loss vectorially subtracts from
insertion loss, so a good launch design is important, even if your using fancy
de-embedding or loss extraction schemes.
For ADS we used measure-modeled based de-embedding, for Simbeor we used GMS
parameters. Simbeor uses line segments, in ADS we used lines and Beatty
standards. The ADS approach is described on Keysight/WRT Tutorial we did last
DesignCon and is on our website, 32Gbpsec Test Fixture Design, and Simbeor has
numerous app notes on GMS method.
Our measurements were validated using a good S-parameter work flow, checking
for passivity, causality, with a validated calibration using Stepped impedance
standard and precision wideband terminators, along with short THRU. We pass
our S-parameters through Simbeor for our post measurement work flow.
- Al
Products for the Signal Integrity Practitioner
Alfred P. Neves
Chief Technologist
Office: 503-679-2429
www.wildrivertech.com
On Apr 7, 2015, at 5:44 PM, Scott McMorrow <scott@xxxxxxxxxxxxx> wrote:
to follow on, stripline or microstrip? are you deembedding the traces to
remove fixturing from the loss measurement.
Scott McMorrow
Consultant - R&D
16 Stormy Brook Rd
Falmouth, ME 04105
(401) 284-1827 Business
http://www.teraspeed.com
On Tue, Apr 7, 2015 at 5:13 PM, Tom Dagostino <tom@xxxxxxxxxxxxxxxxx> wrote:
Joel
What is your test method? How are you connecting to the board? What test
equipment are you using? Are you measuring the same net on both boards?
Tom Dagostino
Teraspeed Labs
9999 SW Wilshire Street
Suite 102
Portland, OR 97225
tom@xxxxxxxxxxxxxxxxx
www.teraspeedlabs.com
971-279-5325 office
503-430-1065 cell
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On
Behalf Of Joel Brown
Sent: Tuesday, April 07, 2015 2:01 PM
To: SI-List
Subject: [SI-LIST] Why is my PCB loss so high?
We have had several boards made from Isola FR408HR.
My understanding is that at 3 GHz loss should be about 0.3 db / inch.
On one board I am measuring about 0.76 db / inch, on another 1.4 db / inch.
What can account for this?
Thanks
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