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

I don't know what people here mean by theoretical formula but the so-called
"double series expansion" is a semi-analytical solution to the wave equation
in two dimensional rectangular structures. It enjoys the closed form
derivation of Green's function for certain shapes including the rectangle.
As long as the underlying basic assumption is met (i.e. the dielectric
thickness being electrically much smaller than the lateral dimensions of the
plane) it's as rigorous as any numerical EM code. For practical PCBs, in the
case of any deviation from its results for frequencies below 1Ghz, I would
be tempted to check my numerical EM code settings first. In the past I did
comparison against VNA measurements for planes with dielectric substrates
ranging from 1 to 5  thou thick and obtained excellent match up in this
frequency range.
Another point is, despite its high precision, HFSS is very clumsy for this
kind of structures. That's why ANSOFT developed SIwave (kind of 2D HFSS) ,
which suits way better to planar structures. I think it's the right tool to
use in this case.
Regards

Ihsan

On 10/28/06, Zhangkun <zhang_kun@xxxxxxxxxx> wrote:
>
> > Dear All
> >
> > I have maken some more simulation. I confirmed that the structure of
> ports would not greatly affected the transfer impedance although it will
> affect the self impedance. I have checked my HFSS simulation, there is no
> problem.
> >
> > Another point, the measurement result and the theoritical result about
> rectangle power plane pair do not agree to each other when the dielectric is
> about 0.55 mil.
> >
> > Best Regards
> >
> > Zhangkun
> > 2006.10.28
> > ----- Original Message -----
> > From: "Yang Rui" <yangrui@xxxxxxxxxxxxxxxxx>
> > To: "Zhiping Yang" <zyang@xxxxxxxxxxxxxxxx>; <zhang_kun@xxxxxxxxxx>; <
> si-list-bounce@xxxxxxxxxxxxx>
> > Sent: Friday, October 27, 2006 1:31 PM
> > 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.
> >
> > Regards,
> > Yang Rui
> >
> > -----Original Message-----
> > From: Zhiping Yang [mailto:zyang@xxxxxxxxxxxxxxxx]
> > Sent: Friday, October 27, 2006 12:03
> > To: Yang Rui; zhang_kun@xxxxxxxxxx; si-list-bounce@xxxxxxxxxxxxx
> > Subject: RE: [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
> >
> > -----Original Message-----
> > From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
> > On Behalf Of Yang Rui
> > Sent: Thursday, October 26, 2006 8:52 PM
> > To: Zhiping Yang; zhang_kun@xxxxxxxxxx; si-list
> > Subject: [SI-LIST] Re: Transfer Impedance of Regular Power Plane Pair
> >
> > HI, ZhiPing and ZhangKun,
> >
> > From my simulation experience, I had very consistent simulation &
> > measurement results for multilayer power structure up to 18GHz.
> >
> > For HFSS simulation for this type of structure, the size of power/ground
> > plane (horizontal plane) is much bigger than the thickness of the
> > substrate between power and ground plane, HFSS generate the initial mesh
> > is very coarse, therefore the convergence is very slow if without proper
> > intial mesh seeding.=20
> >
> > I would like to take a look of your model, you can drop me a mail.
> >
> > Thank you and Regards,
> > Yang Rui=20
> >
> > -----Original Message-----
> > From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
> > On Behalf Of Zhiping Yang
> > Sent: Friday, October 27, 2006 11:35
> > To: zhang_kun@xxxxxxxxxx; si-list
> > Subject: [SI-LIST] Re: Transfer Impedance of Regular Power Plane Pair
> >
> > Hi Zhang Kun,
> >
> > Two things could cause HFSS simulation results differ from theoretical
> > results.  One is boundary condition and the other one is the excitation
> > port settings.
> >
> > For your case, most likely it was due to port settings.  Did you use via
> > in your HFSS simulation at the port?  The coupling between via and
> > power/ground planes, and coupling between vias could cause resonant
> > frequency changes.=3D20
> >
> > The theoretical equation is based on certain assumptions.  One of them
> > is that E field is vertical between power/ground planes.  In real
> > simulations, any openings on power/ground plane could invalidate this
> > assumption, so it is very difficult to match simulation and theoretical
> > results.
> >
> > Regards,
> > Zhiping
> >
> > -----Original Message-----
> > From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
> > On Behalf Of Zhangkun
> > Sent: Thursday, October 26, 2006 7:10 PM
> > To: si-list
> > Subject: [SI-LIST] Transfer Impedance of Regular Power Plane Pair
> >
> > Dear All
> > In the current research, we found an interesting result about the
> > transfer impedance of regular power plane pair. We need some help to
> > solve the problem. We use HFSS to simulate the impednce of regular power
> > plane pair. Any advice would be helpful.
> >
> > According to the theory, the transfer impedance of regular power plane
> > pair coudl be expressed by means of Double Sigma Function. In the
> > expression, the thickness of dielectric would not affect the shape of
> > the impedance. However, in our simulation, we found out that the
> > frequency location of pole and zero of the impedance is affected by the
> > thickness of the dielectric.
> >
> > Reference Paper:
> > Estimating the Power Bus Impedance of Printed Circuit Boards With
> > Embedded Capacitance, IEEE Trans on Advanced Package, Aug. 2002
> >
> > Best Regards
> >
> > Zhangkun
> > 200610.27
> >
> >
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