[SI-LIST] Re: TDR vs. VNA? Which to purchase?

Dear Ray,

I can get transient simulations to work when there is gain, but not when
there are causality problems, i.e., output prior to input.

Regards,

Paul Levin
Xyratex
_________________

Ray Anderson wrote:
> Paul-
>
> I think the problem manifests itself as non-passivity when the model is
> utilized in a transient simulation. That is why people go to the trouble
> of checking for passivity and doing passivity enforcement on their
> s-parameter data. A non-passive model can cause convergence issues among
> other things.
>
> -Ray Anderson
> Xilinx Inc.
>
>
>   
>> -----Original Message-----
>> From: si-list-bounce@xxxxxxxxxxxxx
>>     
> [mailto:si-list-bounce@xxxxxxxxxxxxx]
>   
>> On Behalf Of Paul Levin
>> Sent: Sunday, February 24, 2008 11:40 AM
>> To: ron@xxxxxxxxxxx
>> Cc: art_porter@xxxxxxxxxxx; kuifeng@xxxxxxxxx;
>>     
> tom_cip_11551@xxxxxxxxx;
>   
>> si-list@xxxxxxxxxxxxx
>> Subject: [SI-LIST] Re: TDR vs. VNA? Which to purchase?
>>
>> Dear Ron,
>>
>> Values in excess of 1.00 aren't necessarily fatal. S-parameters and
>> transient
>> responses estimated from them work just fine for my +26 dB gain
>> amplifiers.
>>
>> Tiny errors at very low frequencies may not matter much for high-speed
>> data
>> transmission anyway. With almost any encoding scheme in use today, it
>>     
> is
>   
>> hard to get much energy into very low frequencies.
>>
>> Regards,
>>
>> Paul Levin
>> Senior Principal Engineer
>> Xyratex
>> _________________
>>
>> ron@xxxxxxxxxxx wrote:
>>     
>>> 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
>   
>>> 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 =
>>>> S-parameter conversion on the Agilent TDR. The option 202 for the
>>>>         
>> 86100C =
>>     
>>>> provides this capability in the instrument. =
>>>> http://cp.literature.agilent.com/litweb/pdf/5989-3110EN.pdf
>>>>
>>>> Note: Not intended as an advertisement, just to make sure the =
>>>> information out there is correct and complete.=20
>>>>
>>>> Art Porter
>>>> Agilent Technologies=20
>>>>
>>>> -----Original Message-----
>>>> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-
>>>>         
>> bounce@xxxxxxxxxxxxx] =
>>     
>>>> 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
>>>> 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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