[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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>   
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