[SI-LIST] Re: Common Mode Return Loss Measurements

Ray,

For passive or linear active DUTs, we use a single-ended VNA and math.
Among other benfits of this technique: you get not only Common, and
Differential return loss, but mode-conversion (common signal reflection
resulting from differential drive, and vice-versa).  Cool, we say.

See paper #95 "Frequency domain characterization for hi speed digital
applications" on our website for an example.

www.gigatest.com

-- Gary

-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Ray Anderson
Sent: Monday, April 21, 2003 3:47 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Common Mode Return Loss Measurements




A couple seemingly simple questions:

1)      What is the usually accepted method for measuring
        common mode return loss  (CMRL) ? (VNA with a balun,
        single ended VNA and math, differential TDR, ????).
        Would a CMRL measurement be the same as a differential
        S11 measurement?

2)      Any practical differences between "common mode return loss"
        and "even mode return loss"? (doesn't common mode imply
        equal amplitudes and same phase while even mode only implies
        same phase ?)

-Ray Anderson
Sun Microsystems

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