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

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From: [email protected]
Date: Tue Dec 21 1999 - 10:58:45 PST

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:[email protected]]
Sent: Thursday, December 16, 1999 6:30 PM
To: '[email protected]'
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: [email protected] [mailto:[email protected]]
> Sent: Thursday, December 16, 1999 7:18 AM
> To: [email protected]
> 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
> [email protected]
> (512)-723-3914
>
>
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