RE: [SI-LIST] : Eye pattern with differencial signals.

About this list Date view Thread view Subject view Author view

From: David Kaiser ([email protected])
Date: Mon Nov 27 2000 - 17:09:36 PST

Tektronics makes a 1.7GHz differential probe that I have had to experience
with. I don't have the part number or probe with me right now. Extremely
convience, but costly. About $4000.00.

David Kaiser
McDATA Corp.
310 Interlocken Pkwy.
Broomfield, CO 80021
(303) 460-4431
[email protected]

-----Original Message-----
From: Degerstrom, Michael J. [mailto:[email protected]]
Sent: Friday, November 24, 2000 1:31 PM
To: [email protected]
Subject: RE: [SI-LIST] : Eye pattern with differencial signals.

I think Andrew makes some very good points. Sometimes you can get
by with a signal ended measurement. But I was just doing probing
of PCML (CML run from a positive supply) and the measured
eye was lousy but the bit-error-rate was fine. Since CML
references it voltage levels from the most positive rail and
you must probe with a ground a 0 volts, then the probe picks
up power to ground noise.

I have a hard time finding good diffential probes (and good
single-ended probes as well). So I often take existing probes
and apply my own ground leads. For differential measurements
I often do not use a ground lead. Also, I've set the scope
up to measure vtrue-vfalse and have noticed a much cleaner
signal as a result.

Mike

_______________________________________________________________

> -----Original Message-----
> From: Ingraham, Andrew [mailto:[email protected]]
> Sent: Monday, November 06, 2000 8:48 PM
> To: [email protected]
> Subject: RE: [SI-LIST] : Eye pattern with differencial signals.
>
>
> > According to Agilent (and using Agilent equipment), you may
> use a single
> > probe.
> > Connect
> > the probe tip to one of your +/- nets and the ground tip to
> GND. They do
> > offer
> > differential probes, but they are not be high bandwith capable.
>
> That's OK as long as there is no significant common-mode
> noise. If there is
> (added noise or +/- skew), then the single ended measurement
> would be in
> error. Common-mode noise would corrupt the eye pattern; the
> differential
> receiver would see bigger margins than you would measure.
>
>
>
> **** To unsubscribe from si-list or si-list-digest: send e-mail to
> [email protected]. In the BODY of message put: UNSUBSCRIBE
> si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP.
> si-list archives are accessible at http://www.qsl.net/wb6tpu
> ****
>

**** To unsubscribe from si-list or si-list-digest: send e-mail to
[email protected]. In the BODY of message put: UNSUBSCRIBE
si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP.
si-list archives are accessible at http://www.qsl.net/wb6tpu
****

**** To unsubscribe from si-list or si-list-digest: send e-mail to
[email protected]. In the BODY of message put: UNSUBSCRIBE
si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP.
si-list archives are accessible at http://www.qsl.net/wb6tpu
****

About this list Date view Thread view Subject view Author view

This archive was generated by hypermail 2b29 : Tue May 08 2001 - 14:30:16 PDT