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

TRY again. This reply seems to be block by somewhere. Sry for multi-sending if 
you received more than one copy.
________________________________

From: Yang Rui
Sent: Fri 10/27/2006 3:53 PM
To: 'zyang@xxxxxxxxxxxxxxxx'; si-list
Cc: Yang Rui
Subject: RE: [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=0 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.


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

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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