FreeLists / si-list / [SI-LIST] Re: Return loss measurement - odd result - why?

["Tom Dagostino" <tom@xxxxxxxxxxxxx>]

Dotter

You may have a stub, a set of discontinuities or some other structure =
that
sets up a quarter wavelength resonator causing this.

Is your system terminated?  Do you have clean launches into the DUT?  Do =
you
have other pieces of equipment or structures hanging onto the net you =
are
trying to measure?  Are there some high Q elements in the net?

Have you thought of making a simple model of what you are measuring and =
see
if there are any clues in the structure of the actual measurement setup =
that
could contribute to these results you are seeing?

Tom Dagostino
Teraspeed(R) Labs
13610 SW Harness Lane
Beaverton, OR 97008
503-430-1065
tom@xxxxxxxxxxxxx=20
www.teraspeed.com=20

Teraspeed Consulting Group LLC
121 North River Drive
Narragansett, RI 02882
401-284-1827

-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] =
On
Behalf Of dotter
Sent: Wednesday, May 16, 2007 3:25 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Return loss measurement - odd result - why?


Hi,
I've been making return loss measurements of balun coupled ADC input=20
using spectrum analyser with tracking gen and a return loss bridge.

The return loss shows a regular "oscillation" of amplitude vs frequency=20
of about 10dB with an extremely regular period of 100MHz across a=20
bandwidth of about 1GHz.

Is this an artifact? It seems extremely stable and unrelated to any=20
clocks in the circuit.
Any ideas what would cause this?

Apologies if this is too far OT!

Dotter

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