Thanks -Lyndell
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Todd Westerhoff
Sent: Wednesday, September 23, 2015 7:54 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: TDR obtained by fourier transform of S11
It took me a while to wrap my head around what TDR plots were telling me as
well.
Mike Steinberger's article "TDR: Reading the Tea Leaves" helped me
understand this better.
You'll find a copy of the article here:
http://www.sisoft.com/elearning/s-parameter-resources/s-parameters.html
You'll also find links to our recent Webinar on testing S-parameters, should
you be interested.
Todd.
Todd Westerhoff
VP, Semiconductor Relations
Signal Integrity Software Inc. . www.sisoft.com
6 Clock Tower Place . Suite 250 . Maynard, MA 01754
(978) 461-0449 x124 . twesterh@xxxxxxxxxx
"I want to live like that"
-Sidewalk Prophets
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Scott McMorrow
Sent: Wednesday, September 23, 2015 9:20 AM
To: jun zhang <zhangjun5960@xxxxxxxxx>
Cc: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: TDR obtained by fourier transform of S11
Dude. What you are seeing is the accumulated round trip resistance of the
interconnect that you are measuring. If it is a uniform transmission line,
then you can correct the TDR profile by removing the TDR slope (which is the
resistance) and recover the true impedance.
BTW, the first time that all of us old timers looked at a TDR, we thought
the same as you.
Happy TDRing
Scott
Scott McMorrow
Consultant - R&D
Teraspeed Consulting - A Division of Samtec
16 Stormy Brook Rd
Falmouth, ME 04105
(401) 284-1827 Business
http://www.teraspeed.com
On Wed, Sep 23, 2015 at 9:10 AM, jun zhang <zhangjun5960@xxxxxxxxx> wrote:
Hi experts,unique.
I observe a phenominon about TDR obtained by fourier transform of S11.
I notice that it gradually increases along the time axis. What does
this mean?
It seems that the impedance at each position is related to, but not
indepedant of that at other position. Characteristic impedance is
so can TDR not reflect characteristic impedance? Or early time TDR
still can reflect characteristic impedance? A designcon paper mentions
the phenominon and find the cause is frequency-depend loss. So I think
this is a intrinstic drawback of TDR. It can't show accurately the
impedance at each position of the link path.
Do you agree with me?
--
best wishes,
Jun Zhang
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