Re: [SI-LIST] : Fwd: Probing power plane with analyser.

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From: Bob Lewandowski (Bob.Lewandowski@Vixel.com)
Date: Thu Sep 28 2000 - 10:48:21 PDT


Picosecond Pulse Labs (www.picosecond.com) manufactures coaxial DC blocks that
operate from 700 Hz to >26 GHz (3 dB BW) and stand off 16 Vdc.

You can also get a .086 in. diameter 'Semi Flex' coax cable from Tensolite/QMI
(www.qmiinc.com). It has tin dipped bare outer braid and is more flexible than
conventional semi-rigid coax. Cut the cable, strip back the outer shield and
dielectric to expose about 0.1" of center conductor, solder the the coax shield
to the ground pad of a bypass capacitor location, and the center conductor to
the capacitor pad connected to the power bus. Then insert the dc block ahead of
the 8591E and look at the spectrum of the noise on the bus.

You can also measure bus impedance as a function of frequency by connecting a
network analyzer to the same point by using a Smith Chart plot of S11.
Calibrating the NWA and establishing the correct reference plane can be somewhat
tricky in this process. The inductance of the traces and vias connecting the
coax to the power and ground planes limit the low end measurement range at
higher frequencies, but it may yield a useful comparison.

---Bob Lewandowski
    Vixel Corp.

Barry Ma wrote:

> ------- Start of forwarded message -------
>
> To: "'EMC - PSTC Forum'" <emc-pstc@majordomo.ieee.org>
> Cc: Roman Seifert <Seifert@ali.com.au>
> Subject: Probing power plane with analyser.
> From: "Cameron O'phee" <O'phee@ali.com.au>
> Date: Thu, 28 Sep 2000 11:59:24 +1100
>
> Hello All,
>
> I have been asked by one of our design engineers if I can measure the RF
> signature on the 3v plane on one of our PCB designs. The purpose of this is
> to compare it to proposed changes for cost reduction, ie removal of bypass
> caps. I would assume I need some sort of CDN but I have no designs for this
> application. Does anyone have any ideas on how I can safely probe a 3v DC
> power rail with an EMC analyser (HP8591E)?
>
> Regards,
>
> Cameron O'Phee.
> EMC & Safety Precompliance.
> Aristocrat Technologies Australia.
>
> Telephone : +61 2 9697 4420
> Facsimile : +61 2 9663 1412
> Mobile : 0418 464 016
>
> Thanks.
> Best Regards,
> Barry Ma <bma@anritsu.com>
> ANRITSU www.anritsu.com
> Morgan Hill, CA 95037
> Tel. 408-778-2000 x 4465
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