[SI-LIST] Re: TDR vs. VNA? Which to purchase?
- From: "Deibele, Craig E." <deibele@xxxxxxxx>
- To: ron@xxxxxxxxxxx, art_porter@xxxxxxxxxxx
- Date: Mon, 25 Feb 2008 08:35:08 -0500
One more problem with a vna -- if any sharp resonances occur in the band
you are trying to measure, the vna can completely miss it.
But, I find a vna to be one of the most useful tools. And I recommend
having one of each.=20
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of ron@xxxxxxxxxxx
Sent: Sunday, February 24, 2008 11:43 AM
To: art_porter@xxxxxxxxxxx
Cc: kuifeng@xxxxxxxxx; tom_cip_11551@xxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: TDR vs. VNA? Which to purchase?
Guys
The S-Parameter measurements are very accurate, but have a problem in
that close to DC, minor noise usually corrupts the data with the values
exceeding 1.00 even by a microvolt which then cannot converge when used
as a model in used in time domain simulations.
It is necessary to remove any value that exceeds 1.00
Also, it is necessary to add a DC line.
However, S-Parameters derived from TDR measurements will not have these
two problems and can be used directly.
...............Just another reason for the TDR approach................
BTW Both TEK and Agilent TDR works well if the DUT is brought clost=20
to the TDR head so short 3" semirigid cables can be used.
Both instrument have umbilicals to remote the head to the bench
or in the air.
However, TEK TDR head is smaller, lighter and easier to handle
when remoted to the test area or benchtop.
Ron Miller
art_porter@xxxxxxxxxxx wrote:
>Just a note: "3rd party SW" is not required for time-domain to =3D=20
>S-parameter conversion on the Agilent TDR. The option 202 for the=20
>86100C =3D provides this capability in the instrument. =3D=20
>http://cp.literature.agilent.com/litweb/pdf/5989-3110EN.pdf
>
>Note: Not intended as an advertisement, just to make sure the =3D=20
>information out there is correct and complete.=3D20
>
>Art Porter
>Agilent Technologies=3D20
>
>-----Original Message-----
>From: si-list-bounce@xxxxxxxxxxxxx=20
>[mailto:si-list-bounce@xxxxxxxxxxxxx] =3D On Behalf Of kuifeng hu
>Sent: Tuesday, February 19, 2008 12:14 PM
>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=20
>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=20
>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=20
>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
>>=3D
>> =20
>>
>=3D3D
> =20
>
>>need the scope for other measurements as well?=3D3D20
>>
>>Art Porter
>>Agilent Technologies
>>
>>-----Original Message-----
>>From: si-list-bounce@xxxxxxxxxxxxx =3D
>> =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 =3D
>> =20
>>
>personally =3D3D
> =20
>
>>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 =3D
>> =20
>>
>=3D3D
> =20
>
>>also
>>show the excess capacitance/inductance.
>>
>>But again, there are exceptions, depending on the interface you want =
=3D
>> =20
>>
>to
> =20
>
>>characterize. Take the XFP interface for instance. It has some of the=20
>>electrical interconnect parameters defined in terms of DS11, DS21. If=20
>>=3D
>> =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
>>=3D
>> =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 =3D
>>> =20
>>>
>know,
> =20
>
>>>technology changes pretty fast, and what might have been true a year=20
>>>=3D
>>> =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 =
=3D
>>> =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 =3D
>>> =20
>>>
>are
> =20
>
>>>comprised of many differential pairs, routed closely together. =3D
>>> =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 =3D
>>> =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
>>> =3D
>>> =20
>>>
>=3D3D
> =20
>
>>the
>> =20
>>
>>>VNA solution would have been the most versatile. However, Tektronix =
=3D
>>> =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
>>> =3D
>>> =20
>>>
>=3D3D
> =20
>
>>my
>> =20
>>
>>>own predjudice and the marketing hype.
>>>
>>> Thank You
>>> Tom
>>>
>>>
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--
Ronald B. Miller, Microwave/SI Engineer RAIL =3D NOISE + REFLECTIONS
Gigahertz Data Div of MI Corp. \\ // \\ //=20
7721 Sunset Avenue \\// \\//
Newark, CA 94560 ->JITTER<- EYE ->JITTER<-
tel 510-793-4744, //\\ //\\
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