[SI-LIST] Re: Transfer Impedance of Regular Power Plane Pair

HI, Zhiping,

Let's come back to the equation (2) of this paper: "Estimating the Power
Bus Impedance of Printed Circuit Boards With Embedded Capacitance, IEEE
Trans on Advanced Package, Aug. 2002"

Following assumptions are made: power plane and ground plane are assumed
to be PEC, the four side walls of substrate are assumed to be PMC. These
have been clearly specified in the paper. But there is one more
assumption was made which is not mentioned in the paper, which is:
Kz=3D0 because of the distance between power and ground plane are too
small compared with the plane size, which means the cutoff frequency of
Z-direction guided mode is much higher than our current practical
consideration, so we can ignore it. Therefore the equation(2) stands
right. If Kz is needed to be taken into consideration, I believe you can
find more rigorous 3-D cavity mode expansion formular.

And the above equation is for bare rectangular shape power/ground pair,
since Kun is doing comparison between HFSS simulation with this
equation, I don't think there is any perforation or via structure in his
simulation model. Please correct me if I am wrong. Even in HFSS
simulation model, there are few small vias included for measurement
purpose, the introduce inductance is still trivial comparing with the
inductance from the plane itself, I don't expect this factor will shift
the resoance noticeable.

I would use this equation in different way by comparing the first series
resonance and first few parallel resonances frequency between HFSS
simulation and the resonance predicted by cavity resonance method.=20


I got some problems to send email to Si-List, please ignore the possible
repeated sending.=20

Regards,
Yang Rui

-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Zhiping Yang
Sent: Friday, October 27, 2006 12:18
To: si-list
Subject: [SI-LIST] Re: Transfer Impedance of Regular Power Plane Pair

Rui, Kun's original question is HFSS simulation versus theoretical
formula.  In you case, it is simulation versus lab measurement.  These
are two different comparisons.

Question to Kun, at what frequency, the simulation and theoretical
formula start to differ? And how big the difference is?

Regards,
Zhiping


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