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

Chris,

On reading your email, I get the impression that you had a pigtail on the
coax. This is probably the source of the cable issues, why not try an SMA
connector?

Best Regards
Charles Grasso
Senior Compliance Engineer
Echostar Communications Corp.
Tel:  303-706-5467
Fax: 303-799-6222
Cell: 303-204-2974
Email: charles.grasso@xxxxxxxxxxxx;  
Email Alternate: chasgrasso@xxxxxxxx
 

-----Original Message-----
From: Tom Dagostino [mailto:tom@xxxxxxxxxxxxx] 
Sent: Thursday, April 08, 2004 8:40 PM
To: istvan.novak@xxxxxxxxxxxxxxxx; chris_landrum@xxxxxxxxxx;
si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Wacky power plane impedance measurements

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
>
>
>
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