What's Good About The SPB16.2 PCB SI Release? Full Wave Field Solver!

7 Jan 2009 • 6 minute read

The SPB16.2 PCB SI release now contains the Electromagnetic Solution 2D Full Wave field solver (EMS2D).

High density interconnect on PCB and packaging designs with signal switch rates over 5 Gpbs require model characterizations that can support frequency ranges from DC up to THz. Within this wide spectrum, electrical resonance, oscillation, signal dispersion and EM radiation are all likely and must be accounted for. Static or Quasi-static characterization such as BEM2D is not able to address these high frequency issues. Skin effect and dielectric loss are analyzed by simple formulation or empirical equations. Therefore, a full-wave solution is needed to handle these electromagnetic interaction effects.

The Electromagnetic Solution 2D Full Wave field solver (EMS2D) provides the full-frequency range analysis from DC, through the middle frequency range which covers the skin effect, to the THz range of the electromagnetic interactions which address resonances, radiations and EM signal integrity issues.
EMS2D is implemented using the finite element method (FEM), which complements Allegro's moment-based BEM2D field solver. EMS2D combines multiple EM computation modules, static, quasi-TEM, and full-wave analysis. Additionally, EMS2D is able to analyze arbitrary transmission line-type and waveguide structures over PCB cross-sections and provide characterized models in table format.

The EMS2D full wave field solver supports the following capabilities:

Coplanar Waveguide Characterization

EMS2D supports analyses of coplaner waveguide (CPW) structures, including single and differential coupled CPWs in differential pair, microstrip, or stripline types. There's a good bit of technical details to this capability and I'd be happy to provide details to anyone who request it.

Library Enhancements

Interconnect libraries in products that support EMS2D contain a number of enhancements. They include:

CPW structures (as described in the previous section)

Trapezoidal shapes

All trace models support trapezoidal cross-section shapes. A trapezoidal keyword in the model syntax defines traces with a trapezoidal cross-section.

Frequency dependent materials

Material statements in interconnect models are enhanced to accommodate frequency dependent materials.

S-Parameter Extraction

EMS2D extracts S-Parameters when the segment length of interconnect is specified. In such cases, the S-Parameter is output in Touchstone file format (.snp) that you can view in SigWave. The associated frequency points will be specified in the frequency point (.frequency) file. The command line option for this feature is

-sparam <filename.snp> –length <a_number_in_meters> –frequencypointfile <filename.frequency>

These parameters can also be set in the EMS2D Preferences form, accessed from the Analysis Preferences dialog boxes in PCB SI and SigXplorer.

Lossy Transmission Line Modeling in HSPICE

EMS2D analyzes lossy transmission line models with skin effects when provided with sufficient multiple frequency points to cover the skin effect range. The command line option for this feature is

-HspiceRlgcFile <filename.rlc>

Sample lossy transmission line model

* RLGC parameter for a 10-conductor lossy
* frequency-dependent line
10
* L0
3.30259e-07
2.31592e-08 3.31989e-07
5.2425e-09 2.31151e-08 3.31968e-07
1.68377e-09 5.21857e-09 2.31153e-08 3.31983e-07
6.07076e-10 1.68377e-09 5.24252e-09 2.31592e-08 3.30253e-07
1.14758e-07 4.3743e-08 1.33025e-08 4.57592e-09 1.68688e-09 5.27234e-07
4.37807e-08 1.13685e-07 4.35694e-08 1.32506e-08 4.58298e-09 1.11103e-07 5.27028e-07
1.33205e-08 4.35704e-08 1.13627e-07 4.35706e-08 1.33205e-08 3.55001e-08 1.10656e-07 5.26878e-07
4.58298e-09 1.32506e-08 4.35696e-08 1.13684e-07 4.37805e-08 1.26163e-08 3.53548e-08 1.10657e-07 5.27021e-07
1.68688e-09 4.57592e-09 1.33025e-08 4.37428e-08 1.14758e-07 4.70793e-09 1.26163e-08 3.55002e-08 1.11103e-07 5.27227e-07
* C0
1.60927e-10
-5.001e-12 1.60325e-10
-6.73228e-14 -4.97538e-12 1.60325e-10
-6.6084e-15 -6.37752e-14 -4.97553e-12 1.60328e-10
-1.89605e-15 -6.6083e-15 -6.73204e-14 -5.00116e-12 1.6093e-10
-3.35033e-11 -5.08109e-12 -2.67057e-13 -4.97631e-14 -1.53303e-14 1.04442e-10
-5.15666e-12 -3.16128e-11 -5.01411e-12 -2.5613e-13 -5.51085e-14 -1.76851e-11 1.08041e-10
-2.86835e-13 -5.01436e-12 -3.16076e-11 -5.01442e-12 -2.86827e-13 -1.89344e-12 -1.72439e-11 1.08077e-10
-5.51105e-14 -2.56134e-13 -5.01418e-12 -3.16137e-11 -5.15674e-12 -4.36895e-13 -1.79772e-12 -1.72442e-11 1.08042e-10
-1.53306e-14 -4.97637e-14 -2.67051e-13 -5.08117e-12 -3.35043e-11 -1.24375e-13 -4.36891e-13 -1.89343e-12 -1.76855e-11 1.04444e-10
* R0
6.59632
4.98763e-05 6.59632
4.98763e-05 4.98763e-05 6.59632
4.98763e-05 4.98763e-05 4.98763e-05 6.59606
4.98763e-05 4.98763e-05 4.98763e-05 4.98763e-05 6.59606
4.98762e-05 4.98762e-05 4.98763e-05 4.98763e-05 4.98763e-05 6.59632
4.98762e-05 4.98762e-05 4.98762e-05 4.98763e-05 4.98763e-05 4.98762e-05 6.59632
4.98763e-05 4.98762e-05 4.98762e-05 4.98762e-05 4.98763e-05 4.98763e-05 4.98762e-05 6.59632
4.98763e-05 4.98763e-05 4.98762e-05 4.98762e-05 4.98762e-05 4.98763e-05 4.98763e-05 4.98762e-05 6.59606
4.98763e-05 4.98763e-05 4.98763e-05 4.98762e-05 4.98762e-05 4.98763e-05 4.98763e-05 4.98763e-05 4.98762e-05 6.59606
* G0
0
0 0
0 0 0
0 0 0 0
0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
* Rs
4.09704e-08
4.17396e-10 3.85053e-08
3.07264e-11 3.38072e-10 3.85034e-08
4.08935e-12 2.44874e-11 3.37475e-10 3.85039e-08
1.27611e-12 4.29392e-12 3.08721e-11 4.17211e-10 4.09693e-08
3.46744e-09 1.03583e-09 1.38149e-10 3.44633e-11 1.22189e-11 4.84376e-08
1.03871e-09 3.61622e-09 9.80175e-10 1.25833e-10 3.28181e-11 2.34857e-09 4.66542e-08
1.35478e-10 9.80998e-10 3.61822e-09 9.80111e-10 1.35842e-10 4.80654e-10 2.22529e-09 4.66662e-08
3.26349e-11 1.26568e-10 9.79745e-10 3.61629e-09 1.0385e-09 1.5017e-10 4.57766e-10 2.22207e-09 4.66517e-08
1.20266e-11 3.43279e-11 1.3778e-10 1.03609e-09 3.46801e-09 5.83918e-11 1.5234e-10 4.84458e-10 2.34905e-09 4.84387e-08
* Gd
2.22449e-20
-6.91289e-22 2.21617e-20
-9.30604e-24 -6.87747e-22 2.21618e-20
-9.1348e-25 -8.81565e-24 -6.87768e-22 2.21621e-20
-2.62092e-25 -9.13466e-25 -9.30571e-24 -6.9131e-22 2.22453e-20
-4.63117e-21 -7.02359e-22 -3.69153e-23 -6.87876e-24 -2.1191e-24 1.44371e-20
-7.12806e-22 -4.36984e-21 -6.931e-22 -3.54048e-23 -7.61765e-24 -2.44461e-21 1.49345e-20
-3.96492e-23 -6.93135e-22 -4.36912e-21 -6.93144e-22 -3.96481e-23 -2.6173e-22 -2.38362e-21 1.49395e-20
-7.61792e-24 -3.54054e-23 -6.93111e-22 -4.36996e-21 -7.12817e-22 -6.03921e-23 -2.48499e-22 -2.38366e-21 1.49347e-20
-2.11915e-24 -6.87884e-24 -3.69145e-23 -7.0237e-22 -4.6313e-21 -1.71923e-23 -6.03915e-23 -2.61729e-22 -2.44467e-21 1.44373e-20

Command Line Options

Option	Parameter	Default	Description
-in	filename.in		filename.in is the input geometry file. It must be specified when using batch mode.
-out	filename.out		filename.out is the output file which contains the calculated RLGC and ZYTRef data.
-log	filename.log	ems.log	filename.log contains EMS command line option information. For the current version, the default ems.log is always used
-Sparam	filename.snp		This option enables EMS to produce S-parameters to touchstone file filename.snp. Use -zc 50 to specify the reference impedance needed in S-parameter computation. 50 ohms if the default. Use -length 0.0508 to specify the length of the model for S-parameter computation. The length is specified in meters. This line length must be provided when -Sparam is set.
-length	<number>	.0508	Specifies line length (in meters) when S-parameters are enabled.
-fs -fe -np		1 20e9 10	Specifies frequency sweeping range from fs (Start Frequency) to fe (End Frequency) by np points.
-selfinductanceoff	0 \| 1		0: Include self-inductance in RLGC and S-parameter list 1: Exclude self-inductance in RLGC and S-parameter list
-frequencypointfile	filename.frequency		File filename.frequency contains frequency points in one column sorted from low to high. When this option is provided, EMS ignores the other sweep options and does exact computation with this file. This is the preferred and most flexible option.
-freqsweeq	Fixed \| Exact \| Fast	Exact	Fixed uses the same frequency points as in bem2d. The -fs and -np options are ignored. Exact uses the frequency points calculated by EMS based on fs, fe, and np. Fast uses default frequency points.
-meshtype	Rectangle \| Triangle \| Prism \| Brick \| Tetra	Rectangle	This option specifies finite element types. Rectangle is the default for 2D and is the only type supported now.
-meshorder	<number>	1	Mesh order can be 1 t0 3. A higher order results in a more accurate result, but requires longer computation time.
-MoR	1	off	This option is used to speed up the computation for cases with many frequency points. If this option is set to 1, a reduced order model is used. By default, this option is turned off.
-HspiceRlgcFile	filename.rlc	off	This option enables EMS to generate hspice skin-effect trace models in a file named filename.rlc. This hspice model takes Rs(f) and G(f) into account. L(f) is not included. In order to construct this model correctly, at least three frequency points over the skin-effect range are needed. By default, this option is turned off.
-autoswitchtol	0.1		This option specifies when to switch quasi-static extraction to full-wave analysis. 0.1 is the relative error between the two modes. If the error is less than the specification, EMS will continue working on quasi-static extraction.
-AddEmptyLayer	<number>	1.0	This option is for advanced use only. It is used to scale the additional layers added by the solver right above the microstrip structures to increase computational space to model open space.

Feature Licensing

All of the EMS2D field solver features are only available in products that support the new EMS field solver (Allegro PCB SI GXL and XL).

As always, I'm interested in those using this feature in their design analysis and any suggestions you may have.

Jerry Genpart