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Unbalanced Single Stripline on Suspended Substrate (EM Based): SS1LINX

Symbol

Summary

SS1LINX models a section of single stripline with a conductor strip 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 a 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 SS1LIN, however, SS1LINX 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]
L Line length Length L[1]
Acc Accuracy parameter   1
SPSUB Substrate definition Text See[1][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

W. Conductor width 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. SS1LINX does not use Acc in a normal, table-based interpolation mode.

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

Autofill. 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. SS1LINX implies that the ratio W/H2 (H2 is substrate thickness) lies within a predefined range of 0.05≤W/H2≤18.5 . Outside of this range, a model extrapolates output parameters and issues a warning.

  2. Cover height above the 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 SS1LINX fixed parameters. Changes to any fixed parameter start the automatic filling process (if AutoFill is set to 1), the length of which depends on the Acc value.

  3. You can change any fixed parameter to create corresponding tables.

  4. 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 a substrate dielectric constant different from those supplied with AWR Microwave Office software, you need to set ErNom = Er = needed-value-of-dielectric-constant, set AutoFill = 1 and simulate.

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

If you wish to implement values outside of a specified range of W/H2 (see the Parameter Restrictions and Recommendations section), you can use the SS1LIN 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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