[SI-LIST] Re: Wacky power plane impedance measurements

  • From: "Tom Dagostino" <tom@xxxxxxxxxxxxx>
  • To: <istvan.novak@xxxxxxxxxxxxxxxx>, <chris_landrum@xxxxxxxxxx>,<si-list@xxxxxxxxxxxxx>
  • Date: Thu, 8 Apr 2004 19:40:15 -0700

Do you have a grounding problem between the signal source and the Spectrum
Analyzer?


Tom Dagostino
Teraspeed Consulting Group LLC
Device Modeling Division
13610 SW Harness Lane
Beaverton, OR 97008
503-430-1065
tom@xxxxxxxxxxxxx <mailto:tom@xxxxxxxxxxxxx>


Teraspeed Consulting Group LLC
2926 SE Yamhill St.
Portland, OR 97214
http://www.teraspeed.com

Teraspeed (SM) is the service mark of Teraspeed Consulting Group LLC


-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Istvan NOVAK
Sent: Thursday, April 08, 2004 5:41 PM
To: chris_landrum@xxxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Wacky power plane impedance measurements


Chris,

You mention spectrum analyzer... was the source a built-in tracking
generator?  Or did you mean network analyzer?

Beyond the points that other people already pointed out, you may
experience sensitivity to cable location if the IF bandwidth is
unnecessarily wide, and/or if accidentally you mix up the power
and ground connections inj the two cables.  This means if you
connect accidentally the braid from the source cable to the center of
the receive cable.

I hope this helps.

Istvan Novak
SUN Microsystems


----- Original Message -----
From: "Landrum, Chris" <chris_landrum@xxxxxxxxxx>
To: <si-list@xxxxxxxxxxxxx>
Sent: Thursday, April 08, 2004 11:02 AM
Subject: [SI-LIST] Wacky power plane impedance measurements


> Hi all,
> I am running an experiment where I am attempting to measure the power
plane
> impedance of a PCB. The PCB is only populated with capacitors. I am using
a
> spectrum analyzer to plot the freq response. I have two pieces of 50 Ohm
> shielded cable where I have cut the ends to expose the shield and the
center
> conductor. I have then soldered the shield to a large cap at GND and the
> conductor to the other side of the cap at PWR. I have done the same for
the
> second cable at some arbitray distance from cable #1.
> I have noticed that my measurement is EXTREMELY sensitive to cable
movement.
> The results will also change when I simply touch the N-type adapter of the
> SA. I am sure there is a good connection to the PCB, as I have wire tied
the
> cable to the PCB so as not to allow movement at the points of contact. The
> cables may be approx 2ft in length (matched), and I have tried shorter
> lengths with the same result. I have also tried higher quality cables.
>
> Is this result due to coupling? Has anyone performed such a measurement
> without the varying result? Perhaps someone who has can describe their
> set-up.
>
> Thanks.
> Chris
>
>
>
> ------------------------------------------------------------------
> To unsubscribe from si-list:
> si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
>
> or to administer your membership from a web page, go to:
> //www.freelists.org/webpage/si-list
>
> For help:
> si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>
> List FAQ wiki page is located at:
>                 http://si-list.org/wiki/wiki.pl
>
> List technical documents are available at:
>                 http://www.si-list.org
>
> List archives are viewable at:
> //www.freelists.org/archives/si-list
> or at our remote archives:
> http://groups.yahoo.com/group/si-list/messages
> Old (prior to June 6, 2001) list archives are viewable at:
>   http://www.qsl.net/wb6tpu
>
>

------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field

or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field

List FAQ wiki page is located at:
                http://si-list.org/wiki/wiki.pl?Si-List_FAQ

List technical documents are available at:
                http://www.si-list.org

List archives are viewable at:
                //www.freelists.org/archives/si-list
or at our remote archives:
                http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu


------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field

or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field

List FAQ wiki page is located at:
                http://si-list.org/wiki/wiki.pl?Si-List_FAQ

List technical documents are available at:
                http://www.si-list.org

List archives are viewable at:     
                //www.freelists.org/archives/si-list
or at our remote archives:
                http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu
  

Other related posts: