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2 Suspended Substrate Edge Coupled Symmetric Striplines (EM Quasi-Static Based): SS2CLINX

Symbol

Summary

SS2CLINX models a section of two symmetric edge coupled striplines with conductor strips placed on the upper surface of a suspended substrate (suspended substrate is a single layer substrate sandwiched between two infinite grounded planes and separated from them with air layers).

This model is constructed as an X-model (table-based interpolation) using the results of an EM 2-D quasi-static cross-sectional analysis based on Method of Moments. For a more detailed discussion of the X-models see EM-based Models (X-models) . EM 2-D quasi-static analysis is the same method as that used in the SS2CLIN model, however, SS2CLINX gains large computational speed increases due to the table-based interpolation.

Parameters

Name Description Unit Type Default
ID Element ID Text TL1
W Conductor width Length W[1]
S Spacing between conductors Length W[1]
L Line length Length L[1]
Acc Accuracy parameter   1
SPSUB Substrate definition Text See[2]
*AutoFill Autofill database if not equal to 0   0

[1] User-modifiable default. Modify by editing under $DEFAULT_VALUES in the default.lpf file in the root installation directory.

[2] If only one SPSUB is present in the schematic, this substrate is automatically used. If multiple SPSUB substrate definitions are present, you must specify which to use.

* indicates a secondary parameter

Parameter Details

W. Conductor width is an independent parameter.

S. Spacing between conductors is an independent parameter.

Acc. The input parameter Acc is an accuracy parameter influencing the EM 2-D quasi-static cross-sectional analysis, and can range from 1 to 10. This value is used to automatically fill the model tables if the necessary table is missing and the Autofill parameter is set to 1. Higher values of Acc may improve accuracy but also may slow the filling process. SS2CLINX does not use Acc in normal, table-based interpolation mode.

SPSUB. Suspended substrate parameters are listed in the SPSUB model documentation.

Autofill. The AutoFill parameter is a hidden input which allows you to specify that the entire interpolation table should be filled automatically at the current values. To instigate this filling process, this parameter should be set equal to 1. During normal operation, this parameter should be set equal to zero. You can access the hidden parameter by double-clicking on the schematic element.

Parameter Restrictions and Recommendations

  1. SS2CLINX implies that the ratio W/H2 lies within a predefined range of 0.05≤W/H2≤18.0 and the ratio S/H2 lies within a predefined range of 0.025≤S/H2≤70 (H2 is substrate thickness) Outside of these ranges, this model extrapolates output parameters and issues a warning.

  2. Cover height above substrate H1, substrate thickness H2, substrate elevation above ground H3, nominal dielectric constant ErNom, dielectric tangent Tand, relative conductor bulk resistance Rho, and accuracy Acc are fixed parameters. Cadence® AWR® Microwave Office® software provides pre-generated tables for several typical values of SS2CLINX fixed parameters. Changes to any fixed parameter may start the automatic filling process (if Autofill is set to 1), the length of which depends on the value of Acc. You can change any fixed parameter to create corresponding tables.

  3. The dielectric constant Er of the substrate SPSUB is a statistical parameter. It means that models account for the relative deviation of Er from ErNom within 20%; larger deviation demands a new fill of model tables.

Implementation Details

This model was developed under research performed at Cadence Design Systems, Inc. The full set of details of the implementation are considered proprietary in nature.

Layout

This element uses line types to determine its layout. By default, the layout uses the first line type defined in your Layout Process File (LPF). You can change the element to use any of the line types configured in your process:

  1. Select the item in the layout.

  2. Right-click and choose Shape Properties to display the Cell Options dialog box.

  3. Click the Layout tab and select a Line Type.

  4. Click OK to use the new line type in the layout.

See “Cell Options Dialog Box: Layout Tab ” for Cell Options dialog box Layout tab details.

See “The Layout Process File (LPF)” for more information on editing Layout Process Files (LPFs) and to learn about adding or editing line types.

Recommendations for Use

To create new tables for the substrate dielectric constant different from those supplied with AWR Microwave Office software, you must set ErNom = Er = needed-value-of-dielectric-constant, set AutoFill = 1 and simulate.

In exchange for speed increase, small errors resulting from the interpolation should be expected and the range of the input parameters is restricted.

To implement values outside of the specified ranges of W/H2, S/H2 (see "Parameter Restrictions and Recommendations"), you can use the SS2CLIN element.

References

[1] M.B. Bazdar, A.R. Djordjevic, R.F. Harrington, and T.K. Sarkar, "Evaluation of quasi-static matrix parameters for multiconductor transmission lines using Galerkin's method," IEEE Trans. Microwave Theory Tech., vol. MTT-42, July 1994, pp. 1223-1228

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