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What's Good About ABIML in PCB SI? It's in SPB16.2!

Comments(0)Filed under: PCB design, Allegro, SPB 16.2, SI, ABIML

First - ABIML is an acronym for Algorithm-Based Interconnect Model Library.

Currently, the model in the interconnect model library (IML) can only be reused by matching model name, model type, or exact "TraceGeometryData", which includes key information such as shield layer, dielectric layer, trace layer and the exact trace physical geometry. If any of the model geometry data is mismatched, the field solver is called to create a new model. In addition, for dynamic analysis, the frequency spectrum must also be matched. This "exact" model matching procedure provides designers the most accurate electrical parameters as our tool can and will still be active in the future.

Interconnect modeling, which relies heavily on electromagnetic computation and optimization, is essential and critical in high-speed electronic circuit design. The more complex interconnect structures require the use of the new EMS2D full wave field solver, where computation is extremely CPU intensive and not practical in interactive design.

The new methodology is to shift the time needed in model generation by building the algorithm-based models off-line through rigorous full-wave EM simulation. These verified models are then reused to generate new required models efficiently without calling the field solver again.

In the algorithm-based interconnect model library (ABIML), interconnect models are all parameterized and validated for their application range with pre-specified accuracy control. When a specific model is requested from this library, the library will try to provide the model by checking if the needed model is within the algorithm range of the existing same kind of models in the library. Otherwise this library calls the field solver to acquire the model.

Algorithm-based interconnect models are designed to greatly enhance simulation times when interconnect models that match simulation criteria cannot be found in existing traditional models. Algorithmic model generation lets you create accurate interconnect models off-line that exactly match not only shield, dielectric, trace and physical geometry layer information but also entire frequency spectrums. These models are then integrated into libraries for reuse in multiple simulations. There is currently no capability for users to create their own ABIML models.

Algorithm-based modeling is optional. You can enable/disable it from the InterconnectModels tab of the Analysis Preferences dialog box in Allegro PCB SI or the Simulation Parameters tab in SigXplorer.



If you turn off algorithm modeling, the PCB SI tools will not search for algorithm-based models. Instead, it will directly engage the selected field solver to create the required model. This process is illustrated in the flow chart below.


I'm curious how many have been using this feature in the SPB16.2 release?

The ABIML libraries are stored in <install_dir>/share/pcb/signal. The syntax of the model contains two sections:

  • Model information such as parameter range, interpolation type, and sweep step type
  • Multiple RLGC data used in model generation

The following is a simple example of the file format.

[Model] abiml_test
[Model Info]
[Field_Solver_Used] ems2d
[ABIML_Version] 1.0
[Model_Type] singletrace
[Num_of_Port] 2
[Num_of_DielectricLayer] 1
[Num_of_ShieldLayer] 1

[Parameter Info]
[Layer] 1
* min max step step_type interp_type ID
[Thickness] 1.0 1.0
[Constant] 1.0 1.0
[Losstangent] 0.0 0.0
[IsShield] YES

[Layer] 2
* min max step step_type interp_type ID
[Thickness] 1.0 2.0 5 linear linear 1
[Constant] 4.4 4.6 3 log 2_order_poly 2
[Losstangent] 0.0 0.0
[IsShield] NO
[End LayerStack]
[conductor] 1
* min max step step_type interp_type ID
[Thickness] 1.0 1.5 5 linear linear 3
[Width] 1.0 10.0 20 linear 2_order_poly 4
[Losstangent] 0.0 0.0
[end CrossSection]
[End Model Info]
[Model Data]
[Data] 1
[R] 1.459500e+01
[L] 6.088700e-07
[G] 0.000000e+00
[C] 5.162900e-11
[Data Condition]
* ID value
1 1.0
2 4.4
3 1.0
4 1.0
[Data] 4725
[R] 3.630000e+00
[L] 4.567500e-07
[G] 0.000000e+00
[C] 7.440100e-11
[Data Condition]
* ID value
1 2.0
2 4.6
3 1.5
4 10.0
[End Model Data]
[End Model]


As always, I welcome your feedback!


Jerry "GenPart" Grzenia


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