[SI-LIST] Re: A question for the instrument guys on TDR and TDT

  • From: "Chris Cheng" <Chris.Cheng@xxxxxxxxxxxx>
  • To: <dmitry.a.smolyansky@xxxxxxxxxxxxxx>
  • Date: Tue, 7 Nov 2006 12:42:24 -0800

Dima,
I have the CSA version of that scope and I have to admit this whole =
discussion started after I made a side by side comparison between the =
CSA8200 and the N5230A on channel measurements.=20
What do you think the possibility of an impulse response option on the =
CSA8200?
And yes, I agree that power distribution or anything deviated that much =
from nominal 50 ohm impedance will be a different beast.=20

-----Original Message-----
From: dmitry.a.smolyansky@xxxxxxxxxxxxxx
[mailto:dmitry.a.smolyansky@xxxxxxxxxxxxxx]
Sent: Tuesday, November 07, 2006 10:22 AM
To: Chris Cheng
Cc: si-list@xxxxxxxxxxxxx
Subject: RE: [SI-LIST] Re: A question for the instrument guys on TDR and
TDT


BTW, it is not precisely "40/60 dB range." Look at the new Tektronix
DSA8200 datasheet, it shows -70 dB at DC and decreases to -40 dB at 50
Ghz (http://www.tek.com/site/ps/85-17654/pdfs/85W_17654.pdf). Granted,
an RF burst would provide a flatter dynamic range, but this is still
pretty impressive for serial data S-parameter measurements (probably not
for PDB characterization though).

Thanks,
=20
Dima Smolyansky
Product Marketing Manager
Tektronix, Inc.
P.O. Box 500, MS 39-111
Beaverton, OR 97077-0001
503-627-7180
503-627-2260 (fax)


-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Chris Cheng
Sent: Monday, November 06, 2006 8:08 PM
Cc: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: A question for the instrument guys on TDR and TDT

I sure would like to see the VNA that can do real system channel =3D
measurements at 100db after fixture and cabling.
On the other hand, even at 40/60db range, a sampling scope may be good =
=3D
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=3D20
different answers,
dependent on priorities.  My answer is that a scope is OK for low=3D20
dynamic range
or low-frequency measurements, in those applications it is cheaper
than=3D20
VNA and
works fine.  On the other hand, VNAs can achieve 100+ dB dynamic
range=3D20
easily;
to get that in a scope, the effective number of bits would need to =
be=3D20
16+, not
available today on fast scopes.=3D20

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 =3D
capable =3D3D
>of doing it but why not ?  The controls are almost there (for the =3D3D
>TDR/TDT) and de-embedding is a simple step of shifting the reference =
=3D
=3D3D
>plane or simple post processing FIR filter (something advance sampling
=3D
=3D3D
>scope can already do). A $40K+ VNA vs. a free firmware upgrade on the =
=3D
=3D3D
>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 =
=3D
TDT
>
>
>Chris,
>
>The answer is yes (as long as the network is 'sufficiently' linear). =
=3D
=3D3D20
>The finite rise time
>shows up as filtering, what happens in all simulations or =3D
measurements=3D3D20
>anyway,
>even if we neglect the effect of risetime.  If you need the impedance =
=3D
of =3D3D
>
>a power
>distribution network, the quantization of the receiving instrument =3D
will=3D3D20
>set the noise floor.
>
>Regards,
>
>Istvan Novak
>SUN Microsystems
>
>Chris Cheng wrote:
>
> =3D20
>
>>I can understand the merit of a step response and direct read out of =
=3D
=3D3D
>>   =3D20
>>
>=3D3D3D
> =3D20
>
>>impedance profile.
>>Will it be easy to also include a mode with a sharp pulse instead of =
=3D
=3D3D
>>   =3D20
>>
>=3D3D3D
> =3D20
>
>>step for an impulse response ? If you have a circuit to generate a =3D
35ps =3D3D
>>   =3D20
>>
>=3D3D3D
> =3D20
>
>>step, can you use it to generate a 35ps pulse also ? I think there are
=3D
=3D3D
>>   =3D20
>>
>=3D3D3D
> =3D20
>
>>steps you can do to convert one to the other but a direct impulse =3D
=3D3D3D
>>response is just too good to pass up.
>>Network analyzer on the cheap.
>>Thanks in advanced,
>>Chris
>>
>>
>>=3D3D20
>>
>>   =3D20
>>
>
> =3D20
>

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