[SI-LIST] Re: Extract an accurate model from TDR IConnect

David,

Use a 50 Ohm cable to model the discontinuity (differentially, that'll
be 100 Ohm).

Generally speaking, you should have no problem doing what you are trying
to do, and 80E04 should be adequate for the USB work you are doing.
Should you want better resolution or bandwidth, there are new modules on
the market right now, with about rise time that is twice as fast as
80E04.

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 DavidLai@xxxxxxxxxx
Sent: Sunday, February 04, 2007 9:52 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Extract an accurate model from TDR IConnect=20

I have a question about extracting an accurate model from TDR IConnect.
The question is that when I want to extract a DUT which the Impedance is
not 50 ohm,=20

(for example, an USB connector which the differential impedance is 90
ohm).=20

Should I need to make a fixture to transfer impedance from single end 50
ohm to differential 90 ohm,

And then connect between TDR and DUT.=20

The purpose is to eliminate the discontinuity that maybe affect the
model accuracy we extract.

Or can I directly use the 50 ohm SMA cable connect the DUT to extract
the model?

The accuracy will be the same or not?

I am worried because the USB connector is very short.

If I directly use 50 ohm SMA cable, I am afraid that the discontinuity
will cover all the model effect.

Please give me some suggestions.

Thanks for help,

I am truly appreciated.

=20

David


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 =20

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