[SI-LIST] Re: TDR vs. VNA? Which to purchase?
- From: <Aubrey_Sparkman@xxxxxxxx>
- To: <dmitry.a.smolyansky@xxxxxxxxxxxxx>, <kuifeng@xxxxxxxxx>, <tom_cip_11551@xxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Tue, 19 Feb 2008 14:49:41 -0600
AS long as we are disagreeing, I would like to quibble about the
**un-qualified** VNA "most accurate" part. I would have agreed if there
had been a qualification about high frequencies and or smaller
structures. Mr. Fourier says that for the same frequency and time
range.... But the two instruments don't usually cover the exactly the
same frequency / time range. =20
Since Tom said:
"What I do for a living is design boards for digital video, that are
comprised of many differential pairs, routed closely together. Rising
edges are in the neighborhood of 100 ps. I want to be able to find and
modify discontinuities (either capacitive or inductive), determine
crosstalk between the pairs and measure jitter"
The "find and modify discontinuities" part makes me want to recommend
TDR.
Aubrey Sparkman=20
"A Measurement for every Model and a Model for every Measurement.
Without Correlation, I don't believe either." - Aubrey Sparkman
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of dmitry.a.smolyansky@xxxxxxxxxxxxx
Sent: Tuesday, February 19, 2008 2:00 PM
To: kuifeng@xxxxxxxxx; tom_cip_11551@xxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: TDR vs. VNA? Which to purchase?
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,
=3D20
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> wrote:
> If you can only purchase one, one question to ask yourself is: Will I
=3D3D
> need the scope for other measurements as well?=3D3D20
>
> Art Porter
> Agilent Technologies
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx] =3D3D
> 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 =3D3D
> go
> for the TDR, as the hunt for discontinuities and other impedance =3D3D =
> mismatches on a board is far more easy in the time domain. I believe=20
> some models
=3D3D
> 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=20
> electrical interconnect parameters defined in terms of DS11, DS21. If
=3D3D
> 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
=3D3D
> 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>:
> >
> > 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
=3D3D
> or two
> > ago, may not still be true today.
> >
> > I am ready to make a large investment in signal integrity test =
=3D3D
> equipment
> > for my company. I'm probably no more than a week away from the =3D3D
> decision. As
> > some of you will no doubt suggest to get both, let me just say that
I =3D3D
> 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 =3D3D
> edges
> > are in the neighborhood of 100 ps. I want to be able to find and =
=3D3D
> modify
> > discontinuities (either capacitive or inductive), determine
crosstalk
> > between the pairs and measusre jitter (yes, I will need a signal =
=3D3D
> source for
> > that).
> >
> > If this were as little as two years ago I would have believed that
=3D3D
> the
> > VNA solution would have been the most versatile. However, Tektronix
=3D3D
> 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
=3D3D
> solution
> > and the VNA solution.
> >
> > In appealing to the SI group for opinions I am trying to go beyond
=3D3D
> my
> > own predjudice and the marketing hype.
> >
> > Thank You
> > Tom
> >
> >
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