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AWR Version 13

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Design Notes

PCLINE Examples with Comparison to EM

This example shows the use of the PCLINE models. PCLINE models are quasi-static EM based models for lines or coupled lines on a multilayer substrate. A comparison against EM simulation is used to show the accuracy and limitations of the models.

Overview

This example shows how to use the PCNCLIN elements to simulate multiple coupled lines on various layers in a multilayer process (i.e LTCC or PCB). A linear schematic is created using the elements along with parameterized EM structures to model bends on different layers. The comparison highlights the accuracy and limitations of the PCNCLIN models.

Technology

This process is a 6 layer process with each layer being 3.7 mils thick with a relative dielectric constant of 3.7. For consistency purposes between EM And the PCLIN model, the bottom layer of the stack is metal 6 and the top layer is layer 1.

Modeling Bends on Various Layers

There are no discontinuity models for generic multilayer substrates. It is easy to generate parameterized EM structures to model these bends. These EM simulations will run only the unique geometries requested from the schematics using them.

In the "Linear sim coupled lines" schematic, these bends are used as subcircuits. Each of the EM structures is parameterized by using an MBEND and MLIN models in the schematic for the EM structure (with the EM layout active, select the View EM Schematic toolbar button to view this schematic). These models in the EM schematic are only used to generate the proper layout. Variables are used to pass these parameters up through hierarchy. Please see the documentation for more details on parameterized EM documents.

EM simulation vs. Linear Schematic

The schematic named "Linear sim coupled lines" consists of PCNCLIN, PCLIN, and parameterized em structures for bends. The complete schematic represents multilayer routed lines with coupling between layers. The PCNCLIN models account for coupling between layers. The PCLIN models model single lines on a specified layer, and the MTRACE elements model bends on various layers. The EM simulation "Complete Structure" models the same physical layout as the linear schematic. The major difference is that all coupling between elements is accounted for in the EM simulation.

Simulation Plots

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Compare em vs linear complete sMN - M and N are port numbers. These plots show the comparison of the schematic "Linear sim couples lines" and the EM structure "complete structure" for insertion loss for different through paths.

Analysis of the data shows the insertion loss for most of the through paths is the same for both EM and linear simulations. The insertion loss for the through path from port 3 to port 7 is different and can be attributed to the fact that coupling of bend discontinuities is not being accounted for in the circuit analysis (without EM).

PCNCLIN Elements and Layout

The PNCLIN elements also have layout cells that draw on different layers depending on the "CL" parameter. View the 3D view of the linear schematic and observe the lines of the PC4CLIN and the PC2CLIN drawn on different layers. For the PCLIN and the GMLIN models, the way the software determines which line to put them on is different than single layer lines. For single layer lines, they are drawn on the layers defined in a Line Type, so for example,

$LINE_TYPE_BEGIN "M6"

! -> Layer offset minWidth flags

"M6" 0 2e-005 0

$LINE_TYPE_END

This line in the LPF creates a line type named "M6" that will also draw on the layer "M6".

For the PCLIN and GMLIN models, you must define different information in the LPF. For each possible layer of the lines for the model, you must define one "Structure" in the lpf. So for example,

$STRUCT_TYPE_BEGIN "ML_LINE_1"

! -> Layer offset minWidth flags

"M1" 0 2e-005 0

$STRUCT_TYPE_END

defines that any lines with their CL model setting set to layer 1, will draw using the "M1" layer. The critical syntax here is the name of the structure. It must be in the form of "ML_LINE_X", where "X" is the number of the line.

Schematic - Linear_sim_coupled_lines

Schematic Layout - Linear_sim_coupled_lines

EM Structure - Complete_Structure

Graph - compare em vs linear complete s52