[SI-LIST] Re: TDR vs. VNA? Which to purchase?
- From: "Craig Twardy" <ctwardy@xxxxxxxxxx>
- To: "Vinu Arumugham" <vinu@xxxxxxxxx>, <dmitry.a.smolyansky@xxxxxxxxxxxxx>
- Date: Thu, 21 Feb 2008 08:24:25 -0500
Hi Vinu;
I have seen better time resolution than this with a VNA.
The VNA can also resolve phase to less than 10 degrees at 20GHz.
Does that not put the time resolution at something less than 2 psec?
Craig=20
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Vinu Arumugham
Sent: February 19, 2008 4:06 PM
To: dmitry.a.smolyansky@xxxxxxxxxxxxx
Cc: kuifeng@xxxxxxxxx; tom_cip_11551@xxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [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=20
> an example, since this is the company I work for. (it also appears=20
> that Kuifeng's comments are based on his experience with Agilent TDR,=20
> not Tektronix one).
> 1. "3rd party software?" How is that? IConnect, for example, is a=20
> Tektronix tool; the same Tektronix that makes 50 GHz TDR. Perhaps=20
> Kuifeng meant - "separate software tool," but I am not sure that this=20
> is much of a drawback.
> 2. "Complete characterization is time consuming." I presume here we=20
> are talking about 4-port data collection. There are scripts available=20
> from Tektronix to do this using IConnect. Certainly no more time=20
> consuming than with a VNA - as a matter of fact, less time consuming=20
> because of simpler calibration.
> 3. "Need sig gen for eye diagrams." Incorrect. IConnect has fully=20
> automated eye diagram generation using TDR/T or S-parameter data, with
> equalization, eye mask and jitter/noise pass/fail testing. This all=20
> has programmatic interfaces for automation. Far more advanced than=20
> that on a VNA 4. "RLGC model extraction" - can't claim this is as a=20
> disadvantage.
> IConnect has extensive TDR-based behavioral and topological modeling,=20
> 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=20
> have demonstrated appropriate accuracy for TDR-based S-parameter=20
> 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=20
> [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=20
> 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=20
> 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=20
> 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=20
> Ultimate precision required
>
> Kuifeng (Clifford)
>
>
>
>
>
>
> On 2/19/08, art_porter@xxxxxxxxxxx <art_porter@xxxxxxxxxxx> wrote:
> =20
>> If you can only purchase one, one question to ask yourself is: Will I
>> =20
> =3D3D
> =20
>> need the scope for other measurements as well?=3D3D20
>>
>> Art Porter
>> Agilent Technologies
>>
>> -----Original Message-----
>> From: si-list-bounce@xxxxxxxxxxxxx
>> =20
> [mailto:si-list-bounce@xxxxxxxxxxxxx] =3D3D
> =20
>> 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
>> =20
> personally =3D3D
> =20
>> go
>> for the TDR, as the hunt for discontinuities and other impedance =
=3D3D=20
>> mismatches on a board is far more easy in the time domain. I believe=20
>> some models
>> =20
> =3D3D
> =20
>> also
>> show the excess capacitance/inductance.
>>
>> But again, there are exceptions, depending on the interface you want
>> =20
> to
> =20
>> characterize. Take the XFP interface for instance. It has some of the
>> electrical interconnect parameters defined in terms of DS11, DS21. If
>> =20
> =3D3D
> =20
>> 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
>> =20
> =3D3D
> =20
>> 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>:
>> =20
>>> Hi,
>>>
>>> I realize that this thread has been done before, but as we all
>>> =20
> know,
> =20
>>> technology changes pretty fast, and what might have been true a year
>>> =20
> =3D3D
> =20
>> or two
>> =20
>>> ago, may not still be true today.
>>>
>>> I am ready to make a large investment in signal integrity test =
=3D3D
>>> =20
>> equipment
>> =20
>>> for my company. I'm probably no more than a week away from the =3D3D
>>> =20
>> decision. As
>> =20
>>> some of you will no doubt suggest to get both, let me just say that
>>> =20
> I =3D3D
> =20
>> can
>> =20
>>> 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
>>> =20
> are
> =20
>>> comprised of many differential pairs, routed closely together.
>>> =20
> Rising =3D3D
> =20
>> edges
>> =20
>>> are in the neighborhood of 100 ps. I want to be able to find and =
=3D3D
>>> =20
>> modify
>> =20
>>> discontinuities (either capacitive or inductive), determine
>>> =20
> crosstalk
> =20
>>> between the pairs and measusre jitter (yes, I will need a signal =
=3D3D
>>> =20
>> source for
>> =20
>>> that).
>>>
>>> If this were as little as two years ago I would have believed that
>>> =20
> =3D3D
> =20
>> the
>> =20
>>> VNA solution would have been the most versatile. However, Tektronix
>>> =20
> =3D3D
> =20
>> has made
>> =20
>>> 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
>>> =20
> =3D3D
> =20
>> solution
>> =20
>>> and the VNA solution.
>>>
>>> In appealing to the SI group for opinions I am trying to go beyond
>>> =20
> =3D3D
> =20
>> my
>> =20
>>> own predjudice and the marketing hype.
>>>
>>> Thank You
>>> Tom
>>>
>>>
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