[SI-LIST] Re: Question on 2D field solver

  • From: Raj Raghuram <raj.raghuram@xxxxxxxxxxxxxxx>
  • To: ray.anderson@xxxxxxxxxx
  • Date: Thu, 11 Nov 2004 16:54:32 +0000

Ray,

2D field solvers usually leave out the internal inductance and
inductance formulas include them. Could this be the difference? Does
MMTL produce a frequency dependent inductance?

Best Regards,

On Wed, 2004-11-10 at 23:24, Raymond Anderson wrote:
> Here's a question for the field solver guru's on the list:
> 
> I'm currently taking a critical look at the Mayo  MMTL BEM  2D field 
> solver (TNT 1.2.2) that the developers at Mayo have so graciously made 
> freely available under the GNU GPL to the  world. See the si-list 
> message announcing it for download links: 
> (//www.freelists.org/archives/si-list/07-2004/msg00311.html)
> 
> In preparation for doing a series of simulations on some via geometries 
> in packages I decided to validate the accuracy of the MMTL program on 
> some simple geometries that independent high accuracy answers were known 
> for.
> 
> I first tried the zero thickness stripline benchmark suggested by Dr. 
> Rautio at Sonnet Software. 
> (http://www.sonnetusa.com/products/benchmarking/eval_ch3.asp). The 
> results were   about   -0.4% low at 49.8002 ohms.  This compares  
> comparably with a selection of other solvers I've had access to  (but on 
> the low end of the range).
>  
> Mayo MTTL                         49.8002
> Polar CITS25                        49.96
> Agilent Appcad 3.0.2             49.8
> AWR TXLINE                      50.0346
> LINPAR 2.0                          50.03
> LINPAR 1.0                          50.027
> 
> Next I selected the case of a pair of parallel round elements  as a test 
> case. The analytical solution for the inductance of this geometry is 
> given by Grover in chapter 5 of "Inductance Calculations". His formula 
> is an analytic solution based on first principles.
> 
> Using a test case  of  conductors 150 microns in diameter on a 500 
> micron pitch, Grover's equations yields  a loop inductance of  
> 758.84797  nH for 1 meter long conductors. The same problem modeled in 
> the MMTL field solver gives  an answer of  749.4645  nH.  I'm  trying to 
> understand why the field solver answer is about 1.2% low. Is this 
> reasonable for a 2D MOM BEM solver using quasi-TEM assumptions? I've 
> tried modeling it several ways (as  a pair of parallel circular 
> conductors far from ground and as a single circular conductor with it's 
> image reflected across a ground plane) and  am getting the same answer 
> out to at least 2 decimal places. I've also tried upping the density of 
> the meshing  with little real improvement.
> 
> Comments, suggestions and ideas solicited. Thanks!
> 
> -Ray Anderson
> 
> Senior Signal Integrity Staff Engineer
> Advanced Packaging R&D
> Xilinx Inc.
> 
> 
> 
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-- 
Raj Raghuram
Berkeley Design Automation (http://www.berkeley-da.com)
2902 Stender Way
Santa Clara, CA-95054-3213
Tel: 408.496.6600 x203
Cel: 408.390.7614
Fax: 408.496.6633
email: raj.raghuram@xxxxxxxxxxxxxxx

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