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Coplanar 90-Degree Bend (EM Based): CPWBENDX

Symbol

Topology

Parameters

Name Description Unit Type Default
ID Element ID Text CP1
W Conductor width Length W[1]
S Gap width Length W[1]
Wab AirBridge conductor width @ port 1&2 Length W[1]
CPW_SUB Substrate definition Text [2]
*AutoFill AutoFill data base 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 CPW_SUB is present in the schematic, this substrate is automatically used. If multiple CPW_SUB substrates are present, the user must specify.

* indicates a secondary parameter

Parameter Restrictions and Recommendations

  1. 0.25<=(W+2S)/HSub<=4.0

  2. 0.1<=W/(W+2S)<=0.9

  3. 0.1<=Wab/(W+2S)<=0.5

Implementation Details

This circuit component models a co-planar waveguide 90 deg bend including the effects of airbridges which connect the ground planes on either side of a discontinuity. The purpose of these features is to suppress the excitation of a slot line mode between the two ground planes. This model is constructed as an X-model (Table Based Interpolation) using results automatically generated by EMSight and the CPWLINX, CPWABRG models. For a more detailed discussion of the X-models see EM-based Models (X-models). Importantly, an equivalent circuit model is constructed for the discontinuity based upon the EMSight simulation. As the dispersion of co-planar waveguide is minimal, values of the equivalent circuit parameters in the model are assumed frequency independent.

The input parameters W,S and Wab as defined in "Topology" are entered in the default length units.

CPW_SUB allows you to specify the co-planar waveguide substrate.

The AutoFill parameter is a hidden input which allows you to specify that the entire interpolation table should be filled automatically at the current fixed values.

Independent Parameters: W, S, Wab
Scalable Parameters: Frequency
Fixed Parameters: ACCUR, CPW_SUB(Tand, Rho, Is Grounded, Has Cover)
Statistical Parameters: CPW_SUB(Er, Hab, T, Hsub, Hcov)

Recommendations for Use

The CPWBENDX model creates (and uses for modeling) four files with data tables during autofill: Two files with a CPTX prefix for coplanar waveguides, one file with a CPABG prefix for air bridge, and one file with a CP90B prefix that contains CPWBENDX autofill results. The CPTX and CPABG files created by the CPWLINX, CPWTEEX, and CPWABRGX models may also qualify for the CPWBENDX model. If a model finds that the CPTX and/or CPABG files were created with the same set of fixed parameters, it does not generate new files, but uses the existing ones for modeling.

Example projects for autofilling an EM-based model are provided in the /Examples/Circuit Features/Xmodels subdirectory of the Cadence® AWR® program directory.

NOTE: You must initiate an autofill of the EM data table after making any changes to the CPW_SUB element.

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.

CPW elements have special configurations for the defined line types. The center conductor geometry draws on all the layers defined in the line type. The spacing to the ground plane is then drawn on negative layers with the same name as all of the layers in the line type. You must then draw the same layers on the positive layer to complete CPW layout. See “Negative Layers ” for more information on setting up processes for positive and negative layers.

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

References

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

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