[SI-LIST] Re: Proximity effect and the HSPICE w-element field solver
- From: Ray Anderson <Raymond.Anderson@xxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Wed, 19 Sep 2001 09:44:50 -0700 (PDT)
Perhaps others, who are more familiar with this than I, can
comment also, however, here are my thoughts on the subject:
1) I would think that the internal field solver would
take into account current crowding in conductors caused
by the proximity of other conductors. The output of
the field solver will be a set of RLGC matrices that
will be fed to the W element model.
2) The 'gotcha' is that the W element model scales the
skin effect loss by the sqrt(f). I think this is valid
if we can assume equal current flow on all sides of a
conductor. However, when the proximity effect take over
and current is not equally distributed around the periphery
of the conductor I have a feeling that the sqrt(f) dependence
of the skin effect changes to some other function. If so,
the skin effect losses modeled by the W element will lose
accuracy.
Can anyone else comment on this? As I mentioned, I'm not an
expert on this and would welcome any informed input/correction on
the matter.
-Ray Anderson
Sun Microsystems Inc.
>
>
>I have searched the SI-LIST archives and actually came across a thread
>on the HSPICE w-element field solver from June of this year.
>Unfortunately the responses in the thread did not address the original
>question. (They did, however give lots of useful information on
>dielectric loss of FR-4)
>
>At any rate I am beginning a system design which will use 2.5 Gbit/sec
>differential signalling with Infiniband type of signal
>characteristics. My question is whether the HSPICE internal field
>solver (which I have not yet used) includes the effects of proximity
>of differential lines when it calculates the line losses. I assume
>that when two PWB traces are "tightly coupled" as has been discussed
>in this forum, the currents in the traces at high frequencies crowd
>towards the surface due to skin effect AND crowd towards the near
>edges of the traces due to proximity effect. Does anyone know of any
>good resources that specifically discuss the proximity effect at GHz
>frequencies? I would think that for signal edge rates on the order of
>50 ps this could have a profound effect on losses.
>
>Several years ago I used a tool called SIMIAN out of U Texas which I
>believed included proximity effect. If the HSPICE field solver does
>not include these effects does anyone know of another tool which does?
>
>Chris
>
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