RE: [SI-LIST] : W element correlation with measured data

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From: Qu Pingyu (pingyu@ime.org.sg)
Date: Tue Dec 21 1999 - 17:28:05 PST


Hello:

I'm not sure which Ansoft software you are talking about. If you refers to
Quick 3D, it will mesh the conductor to the skin depth if the material was
specified other than perfect conductor as Jim mentioned. However, a constant
current distribution across the cross section will be assumed. Ansoft
engineer told me that there is another Ansoft product called Ansoft EM 3D
field solver, which can handle the uneven current distribution in very thin
conductor. I guess this could give us a more accurate result for those cases
when thickness of conductor is close to skin depth.

Regards

Qu Pingyu

Institute of Microelectronics
11 Science Park Road, Singapore

DID: 65-7705413
Fax: 65-7745747

> -----Original Message-----
> From: Jim_Foppiano@Dell.com [SMTP:Jim_Foppiano@Dell.com]
> Sent: Wednesday, 22 December 1999 2:59
> To: si-list@silab.eng.sun.com
> Subject: RE: [SI-LIST] : W element correlation with measured data
>
> Vadim,
>
> You are correct of you are doing a discrete solution for L.
> In this case it treats the conductors as perfect, all currents
> and therefore all fields are outside the conductor. But if
> you specify a material property such as copper on a conductor
> than the solver will mesh inside the conductor to the skin
> depth of the frequency you specify. In other words it will
> add the inductance due to the magnetic fields inside the
> conductor to the inductance due to the magnetic fields
> outside of the conductor. It will also compute R at the
> skin depth frequency specified. C is treated both at DC
> and high frequency the same, all fields are outside the
> conductor.
> Regards,
>
> Jim
>
> -----Original Message-----
> From: Heyfitch, Vadim [mailto:vadim.heyfitch@intel.com]
> Sent: Thursday, December 16, 1999 6:30 PM
> To: 'si-list@silab.eng.sun.com'
> Subject: RE: [SI-LIST] : W element correlation with measured data
>
>
>
> Jim,
>
> It's my understanding that Ansoft's Maxwell does not creat any mesh
> into the conductor bulk (or skin) when you are extracting AC values.
> Instead
> it only creates the surfice mesh. Therefore there is no point in
> specifying
> 500 MHz instead of 100 MHz just to make sure that the is enough mesh
> layers
> within the skin depth. Please correct me if this is a misconception on my
> part.
>
> Vadim
>
> > -----Original Message-----
> > From: Jim_Foppiano@Dell.com [mailto:Jim_Foppiano@Dell.com]
> > Sent: Thursday, December 16, 1999 7:18 AM
> > To: si-list@silab.eng.sun.com
> > Subject: RE: [SI-LIST] : W element correlation with measured data
> >
> >
> > All,
> >
> > I want to warn everyone that hspice is extremely sensitive to
> > time step.
> > The time step I used in the .sp file produced the results shown.
> > If you vary time step you can get different answers. Also the
> > meshing in Ansoft is sensitive to geometry. I specified frequencies
> > of 100 MHz for the cable geometry and 500 MHz for the stripline
> > geometry in order to avoid problems in skin depth meshing.
> > Ansoft as well as any FE solver at some point may not be able to
> > handle high Aspect ratios (thin wide conductors).
> > Even a round conductor can start to look like a plane at sufficiently
> > high a frequency in terms of skin depth.
> > Regards,
> >
> > Jim
> >
> >
> > Jim Foppiano
> > Signal Integrity
> > jim_foppiano@dell.com
> > (512)-723-3914
> >
> >
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> >
> >

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