[SI-LIST] Re: A question for the instrument guys on TDR and TDT
- From: Istvan Novak <istvan.novak@xxxxxxxxxxx>
- To: Chris.Cheng@xxxxxxxxxxxx
- Date: Mon, 06 Nov 2006 22:50:20 -0500
The 'why not' is an interesting question, and you may get several
different answers,
dependent on priorities. My answer is that a scope is OK for low
dynamic range
or low-frequency measurements, in those applications it is cheaper than
VNA and
works fine. On the other hand, VNAs can achieve 100+ dB dynamic range
easily;
to get that in a scope, the effective number of bits would need to be
16+, not
available today on fast scopes.
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 =
>of doing it but why not ? The controls are almost there (for the =
>TDR/TDT) and de-embedding is a simple step of shifting the reference =
>plane or simple post processing FIR filter (something advance sampling =
>scope can already do). A $40K+ VNA vs. a free firmware upgrade on the =
>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). =20
>The finite rise time
>shows up as filtering, what happens in all simulations or measurements=20
>anyway,
>even if we neglect the effect of risetime. If you need the impedance of =
>
>a power
>distribution network, the quantization of the receiving instrument will=20
>set the noise floor.
>
>Regards,
>
>Istvan Novak
>SUN Microsystems
>
>Chris Cheng wrote:
>
>
>
>>I can understand the merit of a step response and direct read out of =
>>
>>
>=3D
>
>
>>impedance profile.
>>Will it be easy to also include a mode with a sharp pulse instead of =
>>
>>
>=3D
>
>
>>step for an impulse response ? If you have a circuit to generate a 35ps =
>>
>>
>=3D
>
>
>>step, can you use it to generate a 35ps pulse also ? I think there are =
>>
>>
>=3D
>
>
>>steps you can do to convert one to the other but a direct impulse =3D
>>response is just too good to pass up.
>>Network analyzer on the cheap.
>>Thanks in advanced,
>>Chris
>>
>>
>>=20
>>
>>
>>
>
>
>
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List FAQ wiki page is located at:
http://si-list.org/wiki/wiki.pl?Si-List_FAQ
List technical documents are available at:
http://www.si-list.org
List archives are viewable at:
//www.freelists.org/archives/si-list
or at our remote archives:
http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
Other related posts:
