[SI-LIST] Re: Measuring PDN impedance with a VNA?
- From: Mingchang Wang <minwang@xxxxxxx>
- To: "olaney@xxxxxxxxx" <olaney@xxxxxxxxx>, "istvan.novak@xxxxxxxxxxx" <istvan.novak@xxxxxxxxxxx>, "tom_cip_11551@xxxxxxxxxxx" <tom_cip_11551@xxxxxxxxxxx>
- Date: Fri, 14 Sep 2012 13:47:52 +0000
There is a good paper from Agilent on measuring Impedance with VNA, of course,
PDN impedance measurement falls into low impedance category.
Check it out. http://cp.literature.agilent.com/litweb/pdf/5991-0213EN.pdf
Mingchang
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of O. Laney
Sent: Thursday, September 13, 2012 10:44 PM
To: istvan.novak@xxxxxxxxxxx; tom_cip_11551@xxxxxxxxxxx
Cc: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Measuring PDN impedance with a VNA?
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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