[SI-LIST] Re: A question for the instrument guys on TDR and TDT
- From: Scott McMorrow <scott@xxxxxxxxxxxxx>
- To: Chris.Cheng@xxxxxxxxxxxx
- Date: Tue, 07 Nov 2006 11:16:21 -0500
Chris
Samtec Harrisburg has some papers that might be interesting to you:
http://www.samtec.com/reference/articles/pdfs/VNA_TDA_Comparison.pdf
http://www.samtec.com/reference/articles/pdfs/tech-note_TDNA-DynamicRange-and-Sparam-accuracy_web.pdf
Scott McMorrow
Teraspeed Consulting Group LLC
121 North River Drive
Narragansett, RI 02882
(401) 284-1827 Business
(401) 284-1840 Fax
http://www.teraspeed.com
Teraspeed® is the registered service mark of
Teraspeed Consulting Group LLC
Chris Cheng wrote:
> I sure would like to see the VNA that can do real system channel =
> measurements at 100db after fixture and cabling.
> On the other hand, even at 40/60db range, a sampling scope may be good =
> enough for a channel measurement up to a few GHz. Not a bad alternative.
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx
> [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Istvan Novak
> Sent: Monday, November 06, 2006 7:50 PM
> To: Chris Cheng
> Cc: istvan.novak@xxxxxxx; si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: A question for the instrument guys on TDR and TDT
>
>
> The 'why not' is an interesting question, and you may get several=20
> different answers,
> dependent on priorities. My answer is that a scope is OK for low=20
> dynamic range
> or low-frequency measurements, in those applications it is cheaper than=20
> VNA and
> works fine. On the other hand, VNAs can achieve 100+ dB dynamic range=20
> easily;
> to get that in a scope, the effective number of bits would need to be=20
> 16+, not
> available today on fast scopes.=20
>
> If milliohms need to be measured, VNA is hard to beat. For
> tens and hundreds of milliohms or higher, scope would be acceptable.
>
> Regards,
>
> Istvan
>
>
> Chris Cheng wrote:
>
>
>> I would agree. However, the question is not whether the scope is =
>>
> capable =3D
>
>> of doing it but why not ? The controls are almost there (for the =3D
>> TDR/TDT) and de-embedding is a simple step of shifting the reference =
>>
> =3D
>
>> plane or simple post processing FIR filter (something advance sampling =
>>
> =3D
>
>> scope can already do). A $40K+ VNA vs. a free firmware upgrade on the =
>>
> =3D
>
>> sample scope. Which one will you choose !?
>>
>> -----Original Message-----
>> From: Istvan Novak [mailto:istvan.novak@xxxxxxxxxxx]
>> Sent: Monday, November 06, 2006 5:31 PM
>> To: Chris Cheng
>> Cc: si-list@xxxxxxxxxxxxx
>> Subject: Re: [SI-LIST] A question for the instrument guys on TDR and =
>>
> TDT
>
>> Chris,
>>
>> The answer is yes (as long as the network is 'sufficiently' linear). =
>>
> =3D20
>
>> The finite rise time
>> shows up as filtering, what happens in all simulations or =
>>
> measurements=3D20
>
>> anyway,
>> even if we neglect the effect of risetime. If you need the impedance =
>>
> of =3D
>
>> a power
>> distribution network, the quantization of the receiving instrument =
>>
> will=3D20
>
>> set the noise floor.
>>
>> Regards,
>>
>> Istvan Novak
>> SUN Microsystems
>>
>> Chris Cheng wrote:
>>
>> =20
>>
>>
>>> I can understand the merit of a step response and direct read out of =
>>>
> =3D
>
>>> =20
>>>
>>>
>> =3D3D
>> =20
>>
>>
>>> impedance profile.
>>> Will it be easy to also include a mode with a sharp pulse instead of =
>>>
> =3D
>
>>> =20
>>>
>>>
>> =3D3D
>> =20
>>
>>
>>> step for an impulse response ? If you have a circuit to generate a =
>>>
> 35ps =3D
>
>>> =20
>>>
>>>
>> =3D3D
>> =20
>>
>>
>>> step, can you use it to generate a 35ps pulse also ? I think there are =
>>>
> =3D
>
>>> =20
>>>
>>>
>> =3D3D
>> =20
>>
>>
>>> steps you can do to convert one to the other but a direct impulse =
>>>
> =3D3D
>
>>> response is just too good to pass up.
>>> Network analyzer on the cheap.
>>> Thanks in advanced,
>>> Chris
>>>
>>>
>>> =3D20
>>>
>>> =20
>>>
>>>
>> =20
>>
>>
>
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