Hi Alex,
Got it.
Thanks a lot
Alexander Ippich
<alexander.ippich@xxxxxxxxxxxxxxx>äº2015å¹´4æ15æ¥ææä¸åéï¼
The influence of your signal launch is fully in your measurement results.By doing a SOLT calibration at the tip of your microprobes, you have moved
is prominent enough that you see the dB/inch reading of the 4" traces to be
And as you have seen in your results already, the influence of the launch
----------------------------------------------------------------------------------------------------------------------------------------
The only way to clean up the data is to do the de-embedding.
Best regards,
alex
</mail/u/0/s/?view=att&thcbbf24a80491e6&attid=0.1&disp=emb&realattid33111bd0e90102_0.1&zw&atsh=1>
Alexander Ippich
Senior Signal Integrity Engineer
OEM Marketing Europe
Tel: +49 7457 / 605 70 79
Cell.: +49 170 / 63 68 571
e-mail: alexander.ippich@xxxxxxxxxxxxxxx
web: www.isola-group.com
length?
Von: é»æ¶ [mailto:hzyltgg@xxxxxxxxx]
Gesendet: April 15, 2015 09:03 AM
An: Alexander Ippich
Cc: kevin.voegele@xxxxxxxxxxxxxxxx; si-list@xxxxxxxxxxxxx
Betreff: Re: Why are there difference when calculating loss per unit
influnce of signal injection(pad,contact ,via etc. ) to shorter trace is
Hi Alexander,
Thanks,very clear explanation.
We use micro-probe and SOLT calibration to probe tip. That means the
of
Alexander Ippich
<alexander.ippich@xxxxxxxxxxxxxxx>äº2015å¹´4æ15æ¥ææä¸åéï¼
As Kevin pointed our already, if you calibrate your VNA at the connectors
of your measurement cables and do not remove the influence of the
connectors on your PCB and the via / launch structure, you will measure
the following for the short (4") trace:
S21_4" = loss of connector / launch at port 1 + loss of 4" trace + loss
ofconnector / launch at port 2
For the long (8" trace), you are going to measure:
S21_8" = loss of connector / launch at port 1 + loss of 8" trace + loss
constant.connector / launch at port 2
You can see immediately, that S21 for the 8" trace is less than twice the
S21 for the 4" trace, even though the insertion loss per inch is
--------------------------------------------------------------------------
If you measure much longer traces (so the loss of the trace is
significantly higher than the influence of the launch), you will see that
you get the results that you expect.
Another way would be to use TRL calibration of your VNA, which tries to
remove the launch from the results (but as this method relies on having
identical launches for all structures, this has also it downsides) or
post-process your data to do a mathematical de-embedding.
Best regards,
alex
Im--------------------------------------------------------------
Alexander Ippich
Senior Signal Integrity Engineer
OEM Marketing Europe
Tel: +49 7457 / 605 70 79
Cell.: +49 170 / 63 68 571
e-mail: alexander.ippich@xxxxxxxxxxxxxxx
web: www.isola-group.com
-----Ursprüngliche Nachricht-----
Von: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
unitAuftrag von Kevin Voegele
Gesendet: April 15, 2015 03:51 AM
An: hzyltgg@xxxxxxxxx; si-list@xxxxxxxxxxxxx
Betreff: [SI-LIST] Re: Why are there difference when calculating loss per
unit length?
Connectors are a larger percentage of the trace at short distances. Have
you de-embedded cables too?
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of ??
Sent: Tuesday, April 14, 2015 8:41 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Why are there difference when calculating loss per
calculatdlength?
Hi experts,
Sorry for messy code of this question previously .
We characterize insertion loss by xx.xx dB/inch usually.But after we
measured total loss of trace,the loss per unit length calculated by
different length are difference .For example ,one 4inchs trace measured
and calculated loss A dB/inch .and one 8inchs teace measured and
littleloss B dB/inch while other parameters of design are same.The A is a
greater than B alwalys.
My question is:why are there difference ?from measurements?design ?or any
others ?
T hanks
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