[SI-LIST] Re: TDR vs. VNA? Which to purchase?
- From: Vinu Arumugham <vinu@xxxxxxxxx>
- To: dmitry.a.smolyansky@xxxxxxxxxxxxx
- Date: Thu, 21 Feb 2008 12:38:08 -0800
I was referring to Nyquist rate/sampling theorem.
Thanks,
Vinu
dmitry.a.smolyansky@xxxxxxxxxxxxx wrote:
> Craig,
>
> Resolution and resolution are evidently different. If you are talking
> about generic rule of thumb of time resolution being 1/2 the rise time
> of the stimulus (which is supported by the IPC TM-650 document), then I
> believe this is what Vinu and I were quoting. If you are quoting phase
> accuracy, this is a different issue.
>
> Thanks,
>
> 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: Craig Twardy [mailto:ctwardy@xxxxxxxxxx]
> Sent: Thursday, February 21, 2008 5:24 AM
> To: Vinu Arumugham; Smolyansky, Dmitry A
> Cc: kuifeng@xxxxxxxxx; tom_cip_11551@xxxxxxxxx; si-list@xxxxxxxxxxxxx
> Subject: RE: [SI-LIST] Re: TDR vs. VNA? Which to purchase?
>
> 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
>
> -----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
>> 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> 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>:
>>>
>>>
>>>> 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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