[SI-LIST] Re: I have a question related package parasiticextraction
- From: "Neeraj Pendse" <cnepsc@xxxxxxxxxxx>
- To: edpc108@xxxxxxxxx
- Date: Tue, 09 Dec 2003 10:56:09 -0800
Jayprakash:
The definition of inductance that the transmission line equations use is
different from that used by Ansoft SPICELINK. The former is Loop
inductance, which scales with length but the later is Partial inductance
which does not because of self coupling.
KD:
I can think of two reasons for this difference:
#1: source and sink assignments in the two models, especially the
contact of the lead with the wire in the "separate" models
#2: Skin effect: Did you solve AT the freq of interest or did you solve
at the default 100 MHz and "reduced" to the freq you want? In the later
case, one has to be careful because the "reduction" result is generated
by simple formula and is not valid for all frequencies in my opinion.
As for L, there should be and there is difference. Small difference also
expected for C.
Also, there will be some difference due to the fact that the mesh on
each object in the three cases will be different because of the
differences in geometry. I think this error in a simple case can be
reduced by tightening the convergence criterion to let's say 0.2% or so.
Hope that helps...
- Neeraj.
Jayaprakash wrote:
> Hello Patrick,
>
> Then the same argument should hold good even for
> Transmission line model described using telegrapher's
> equation?
>
> By telegrapher's equation, Transmission line has
> uniform RLGC per unit length. The output voltage is
> given by
>
> Vo = exp(-gamma*Line_length)*vin (for a perfectly
> matched system)
>
> Is this description of Transmission line not really
> scalable? (Going by the explanation given below, I
> expect over projection of loss for longer lines than
> actually it is)
>
>
> Thanks and regards,
> Jayaprakash.
>
>
> --- Patrick Zilaro <pzilaro@xxxxxxxxxxxx> wrote: >
> KD,
>
>>There is nothing wrong with the commercial solver.
>>Even if you were to
>>simulate a planar structure such as a trace, you
>>would see that the "parts"
>>do not add up to the "whole". For example, if you
>>simulated a 5mm trace and
>>a 10mm trace using the exact same stack-up, etc. you
>>would find the
>>following:
>>
>>1) capacitance -> 2*5mm trace should be pretty equal
>>to 10mm trace
>>2) (ac) resistance -> 2*5mm trace should be less
>>than the 10mm trace
>>3) inductance -> 2*5mm trace should be even more
>>less than the 10mm trace
>>
>>This is because each segment of the structure
>>interacts with the rest of the
>>segments. So be careful, when you break up a
>>problem, especially since you
>>are introducing error on the optimistic side (where
>>you usually would prefer
>>to be on the pessimistic side).
>>
>>Regards,
>>
>>Patrick
>>
>>-----Original Message-----
>>From: si-list-bounce@xxxxxxxxxxxxx
>>[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of KD
>>KIM
>>Sent: Monday, December 08, 2003 3:59 PM
>>To: si-list@xxxxxxxxxxxxx
>>Subject: [SI-LIST] I have a question related package
>>parasitic
>>extraction.
>>
>>
>>Dear all,
>>I have a question and be happy to write to you.
>>
>>I have simulation the structure composed of only one
>>bonding wire and one
>>lead,
>>using FEM commercial solver, Ansoft Spicelink like
>>below for extraction
>>parasitic values,
>>R, L, and C.
>>
>>I have simulated for below three cases.
>>
>>1. the structure contained only one bonding wire
>>2. the structure contained only one lead
>>3. the structure composed of one wire and one lead
>>
>>I think the value for case 3 equal to the values
>>case 1 added case 2.
>>But the result was not. The difference was about 16%
>>for the Resistance.
>>Of course, other parasitic values also have some
>>differences considerably.
>>Is this difference resulted from the defect of the
>>FEM commercial solver?
>>I want to know that what do you think about it?
>>Please reply to my e-mail.
>
>
>
> =====
> Balachandran Jayaprakash
> Celestijnenlaan,
> 3/61, 3001, Heverlee,
> Leuven, Belgium.
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