[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 23:28:44 -0500
Agree. If you are looking for high-speed channel measurements, it is
fine. I was
referring to PDN measurements.
To continue the 'why not' list, we need to keep in mind that accuracy of
the measurements
is limited by the calibrations. In time domain, the options are
limited. In frequency domain,
we can choose from a wide range of calibration options. As you say, for
simple channel
measurements scopes with postprocessing are OK.
Commercial software is also available to do this, and past DesignCon and
other publications
compared the pros and cons.
Regards,
Istvan
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
>>
>>
>>
>
>
>
------------------------------------------------------------------
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:
