[SI-LIST] Re: TDR vs. VNA? Which to purchase?
- From: dmitry.a.smolyansky@xxxxxxxxxxxxx
- To: <vinu@xxxxxxxxx>
- Date: Tue, 19 Feb 2008 13:46:54 -0800
With 20 GHz TDR, the resolution is 17.5ps.
With 50 GHz TDR, the resolution is 7.5ps.
Thanks,
Dima Smolyansky
EOPL Marketing
M/S 39-111
503-627-7180
________________________________
From: Vinu Arumugham [mailto:vinu@xxxxxxxxx]
Sent: Tuesday, February 19, 2008 1:06 PM
To: Smolyansky, Dmitry A
Cc: kuifeng@xxxxxxxxx; tom_cip_11551@xxxxxxxxx;
si-list@xxxxxxxxxxxxx
Subject: Re: [SI-LIST] Re: TDR vs. VNA? Which to purchase?
With 20 GHz data from a VNA, the time domain resolution is 25ps.
If the TDR approach works to 20Gbps, it seems like the time resolution
must be much better?
Thanks,
Vinu
dmitry.a.smolyansky@xxxxxxxxxxxxx wrote:
Hello,
I would disagree on TDR cons. I would address them using
Tektronix as an
example, since this is the company I work for. (it also
appears that
Kuifeng's comments are based on his experience with
Agilent TDR, not
Tektronix one).
1. "3rd party software?" How is that? IConnect, for
example, is a
Tektronix tool; the same Tektronix that makes 50 GHz
TDR. Perhaps
Kuifeng meant - "separate software tool," but I am not
sure that this is
much of a drawback.
2. "Complete characterization is time consuming." I
presume here we are
talking about 4-port data collection. There are scripts
available from
Tektronix to do this using IConnect. Certainly no more
time consuming
than with a VNA - as a matter of fact, less time
consuming because of
simpler calibration.
3. "Need sig gen for eye diagrams." Incorrect. IConnect
has fully
automated eye diagram generation using TDR/T or
S-parameter data, with
equalization, eye mask and jitter/noise pass/fail
testing. This all has
programmatic interfaces for automation. Far more
advanced than that on a
VNA
4. "RLGC model extraction" - can't claim this is as a
disadvantage.
IConnect has extensive TDR-based behavioral and
topological modeling, so
this is just one of many capabilities that it has.
I do agree on TDR "quick and easy," and VNA "most
accurate" part. We
have demonstrated appropriate accuracy for TDR-based
S-parameter
measurements, however, for datarates all the way to 20
Gbps.
Thanks,
=20
Dima Smolyansky
Tektronix, Inc.
P.O. Box 500, MS 39-111
Beaverton, OR 97077-0001
503-627-7180
503-627-2260 (fax)
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of kuifeng hu
Sent: Tuesday, February 19, 2008 11:14 AM
To: tom_cip_11551@xxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: TDR vs. VNA? Which to purchase?
Hi, Tom
For your question:
TDR Pros:
Live trace ;Intuitive user interface ;Excess reactance
;TDR
normalization; Quick and easy
VNA pros:
Most accurate measurement
Complete characterization
Excellent SNR
RLCG model extraction
Eye diagrams w/o sig gen
TDR cons
Need 3rd party software to do conversion, Agilent PLTS
vs Tek Iconnect
Complete characterization is time consuming
Need sig gen for eye diagrams
VNA cons
Expensive solution (today)
Complex user interface
Use TDR if Data rate < 3 Gb/s Intuitive tool wanted
Quick set-up Easy measurements Simple calibration 1st
order models okay
used for all general applications
Use VNA if Data rate > 3 Gb/s High SNR required
DUT Xtalk < 1% DUT has low insertion loss DUT sensitive
to EMI
Post data analysis needed Ultimate precision required
Kuifeng (Clifford)
On 2/19/08, art_porter@xxxxxxxxxxx
<art_porter@xxxxxxxxxxx> <mailto:art_porter@xxxxxxxxxxx> wrote:
If you can only purchase one, one question to
ask yourself is: Will I
=3D
need the scope for other measurements as
well?=3D20
Art Porter
Agilent Technologies
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx] =3D
On Behalf Of Lars Juul
Sent: Tuesday, February 19, 2008 8:22 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: TDR vs. VNA? Which to
purchase?
Hi Tom.
For characterization and validation of new board
designs, I'd
personally =3D
go
for the TDR, as the hunt for discontinuities and
other impedance =3D
mismatches
on a board is far more easy in the time domain.
I believe some models
=3D
also
show the excess capacitance/inductance.
But again, there are exceptions, depending on
the interface you want
to
characterize. Take the XFP interface for
instance. It has some of the
electrical interconnect parameters defined in
terms of DS11, DS21. If
=3D
you
want to demonstrate compliance you really do
need a VNA to measure it.
For video applications, I'm not sure what the
requirements are, but I
=3D
doubt
a VNA is the answer to your questions, unless RF
is involved.
Hope this helps.
Lars
2008/2/19, Tom Cipollone
<tom_cip_11551@xxxxxxxxx> <mailto:tom_cip_11551@xxxxxxxxx> :
Hi,
I realize that this thread has been
done before, but as we all
know,
technology changes pretty fast, and what
might have been true a year
=3D
or two
ago, may not still be true today.
I am ready to make a large investment
in signal integrity test =3D
equipment
for my company. I'm probably no more
than a week away from the =3D
decision. As
some of you will no doubt suggest to get
both, let me just say that
I =3D
can
not afford both. I will have one or the
other.
I have had the demos and seen the
equipment.
What I do for a living is design
boards for digital video, that
are
comprised of many differential pairs,
routed closely together.
Rising =3D
edges
are in the neighborhood of 100 ps. I
want to be able to find and =3D
modify
discontinuities (either capacitive or
inductive), determine
crosstalk
between the pairs and measusre jitter
(yes, I will need a signal =3D
source for
that).
If this were as little as two years
ago I would have believed that
=3D
the
VNA solution would have been the most
versatile. However, Tektronix
=3D
has made
a lot of progress with their TDR
equipment and with their "Iconnect"
software. Also, there is a big
difference in price between the TDR =
=3D
solution
and the VNA solution.
In appealing to the SI group for
opinions I am trying to go beyond
=3D
my
own predjudice and the marketing hype.
Thank You
Tom
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