[SI-LIST] Re: Ansoft Q2D vs. Q3D
- From: jydeng@xxxxxxxxxxxxx
- To: "Yassin, Adnan" <adnan.yassin@xxxxxxxxx>
- Date: Fri, 20 May 2011 14:10:11 -0700
2D solver is assuming ideal return path and what you get from 2D
solver is loop inductance. For quasi-static tool, if without
post-processing, what you get is partial L. I'm guessing 760nH/m is
partial L.
To get meaning full partial inductance, ports should be
well-defined. For such correlation, you should define ports on ground
plane just underneath the trace terminals and then do post-processing
after getting AC inductance matrix which should be 2x2. Try the
formula L11+L22-2L12 for loop L from partial L
Quoting "Yassin, Adnan" <adnan.yassin@xxxxxxxxx>:
> Steve,
> The trace width is 50um, so according to your calculations, L is
> roughly 760nH/m. I am getting 611nH/m from Q3D. However, Q2D and
> mathematical equations give much lower L.
>
> Thanks,
> -Adnan
>
> -----Original Message-----
> From: steve weir [mailto:weirsi@xxxxxxxxxx]
> Sent: Friday, May 20, 2011 12:00 PM
> To: Yassin, Adnan
> Cc: si-list@xxxxxxxxxxxxx
> Subject: Re: [SI-LIST] Ansoft Q2D vs. Q3D
>
> It appears that the Q3D model is inferring mutual coupling to some
> structure. Perhaps your bounding box is too small.
>
> As a sanity check, in rough numbers, for a 30um height above the plane
> we should expect about 38pH/square which works out to about 2500nH/m at
> 15um width. That is way-off from either of the inductance/length
> figures you obtained. So, something looks fundamentally wrong.
>
> Steve.
> On 5/20/2011 11:27 AM, Yassin, Adnan wrote:
>> Hi Folks,
>> I have a question regarding extraction data using Ansoft Q2D vs.
>> Q3D. I have a simple model consists of a copper trace, 15um wide&
>> 15um high. It is 30um above a reference ground. The dielectric
>> constant of the material between the trace and the GND plane is
>> 3.9. RLCG is extracted at 1.0GHz. The "RL" data I get from Q2D is
>> different than Q3D for the same model (data is below). Can someone
>> explain why the difference? The Q3D model is generated from Q2D
>> model using "Create 3D Design" command in Ansoft. What do I need to
>> do when generating 3D design from 2D design before extracting RLCG?
>>
>> G(mS/m) C(pF/m) R(ohm/m) L(nH/m)
>> Q2D Design 6.81 108.0 123.85 304.14
>> Q3D Design 6.63 108.2 82.17 611.0
>>
>> Thanks,
>> -Adnan
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>
>
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> Steve Weir
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