[SI-LIST] Re: Measuring PDN impedance with a VNA?
- From: Istvan Novak <istvan.novak@xxxxxxxxxxx>
- To: Randy Dawson <rdawson16@xxxxxxxxxxx>
- Date: Fri, 14 Sep 2012 00:33:20 -0400
Randy,
How would you do this in practice? What impedance would you pick for
the min loss pad for measuring an unknown, frequency dependent impedance?
Regards,
Istvan Novak
Oracle
On 9/14/2012 12:14 AM, Randy Dawson wrote:
> A min loss pad solves the match problem, and with 0402 resistors (or
> smaller) at the probe tip solves the reflection issue.
>
> Randy Dawson
> Sencore
>
>
> > Date: Thu, 13 Sep 2012 23:52:00 -0400
> > From: istvan.novak@xxxxxxxxxxx
> > To: olaney@xxxxxxxxx
> > CC: tom_cip_11551@xxxxxxxxxxx; si-list@xxxxxxxxxxxxx
> > Subject: [SI-LIST] Re: Measuring PDN impedance with a VNA?
> >
> > Orin,
> >
> > I know that you know, but just to clarify for those who are not
> familiar
> > with these concepts:
> > the AC Kelvin-probe arrangements need four connections, which means
> > two-port VNAs.
> >
> > Regards,
> >
> > Istvan Novak
> > Oracle
> >
> >
> > On 9/13/2012 10:43 PM, O. Laney wrote:
> > > Since PDN impedances are usually really low compared to 50 ohms,
> > > practical measurements often require Kelvin probe arrangements. Yes,
> > > that implies the need for 4 VNA ports.
> > >
> > > Orin
> > >
> > > ------ Original Message ------
> > > From: "Istvan Novak" <istvan.novak@xxxxxxxxxxx>
> > > To: tom_cip_11551@xxxxxxxxxxx
> > > Cc: si-list@xxxxxxxxxxxxx
> > > Sent: 9/13/2012 6:54:40 PM
> > > Subject: [SI-LIST] Re: Measuring PDN impedance with a VNA?
> > >> Hi,
> > >>
> > >> The type of probe needed depends on the highest frequency you need to
> > >> cover. For low-frequency measurements, say up to 10MHz, you dont even
> > >> need any probes, just two coax cables, and you can use quite long
> > >> pigtails in soldering and the data is still good. With the semirigid
> > >> probes shown in the paper you cite, you can do reasonably good
> > >> measurements up to about a gigahertz. For even higher frequencies you
> > >> need wafer probes.
> > >>
> > >> To measure low impedances with a VNA, you have to make a two-port
> > >> shunt-through connection, which requires two probes and you have
> to make
> > >> sure that the two probes close through the DUT, not before. If you
> > >> connect the two probes together and then you connect the DUT, will
> > >> introduce series resistance and inductance, which will raise the
> error
> > >> floor.
> > >>
> > >> You can find more details in a later paper:
> > >> "Frequency Domain Power Distribution Measurements - An Overview",
> > >> DesignCon 2003 East, High-Performance System Design Conference,
> Boston,
> > >> MA, June 23-25, 2003, which is posted on the same site, or even more
> > >> details in the book Frequency Domain Characterization of Power
> > >> Distribution Networks.
> > >>
> > >> Regards,
> > >>
> > >> Istvan Novak
> > >> Oracle
> > >>
> > >>
> > >>
> > >> On 9/13/2012 8:03 PM, miner_tom Cipollone wrote:
> > >>
> > >>>
> > >>> I have read several references about how to measure the
> impedance of
> > >>> a PCB PDN (power to ground).
> > >>> A VNA can be used to measure these very low impedances but there is
> > >>> usually a catch in terms of the probes that should be used. Agilent
> > >>> says that in order to measure very low impedances "microprobes"
> > >>> should be used. I do not have microprobes.
> > >>> As an alternative, I have considered building a "Dual Semi-rigid"
> > >>> probe as outlined in
> > >>>
> http://www.electrical-integrity.com/Paper_download_files/DC99_ProbesAndSetup.pdf.
> > >>> With respect to the semi rigid probe made from coax, I have two
> > >>> questions:
> > >>> In the diagram shown in the referenced article on page 8, slide 18,
> > >>> the tips of the probes are not shorted together. I would have
> > >>> thought that for this measurement they would be.Up to what
> frequency
> > >>> is this home made apparatus good? Are there alternative methods?
> > >>> Thank You
> > >>>
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