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Stripline Step in Width (Closed Form): SSTEP

Symbol

Topology

Parameters

SSTEP$ is an iCell. See “Intelligent Cells (iCells)” for an explanation.

Name Description Unit Type Default
ID Element ID Text SL1
W1 Conductor width @ node 1 Length W[1]
W2 Conductor width @ node 2 Length W[1]
SSUB Substrate definition Text 2[2]

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

[2] If only one SSUB is present in the schematic, this substrate is automatically used. If multiple SSUB substrate definitions are present, the user must specify.

Implementation Details

This circuit component models a step in the width of the Stripline center conductor. This model includes the reactive components of the step junction analyzed as a zero thickness step of the effective widths of each section. The model does not include any losses associated with this parasitic reactance. The parameters W1 and W2 (Strip Widths) are dimensions entered in the default length units. The parameter SSUB specifies the Stripline Substrate element, which defines additional cross sectional parameters of the transmission line. This model also warns of the possibility of higher order propagating modes if they exist.

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.

Restrictions

0.1≤(W2)/(W1)≤10

Zo>94.25/(εr)1/2 for T≠0 with Zo≡Chracteristic Impedance of Trans Line

T/B≤0.1 recommended

Recommendations for Use

Discontinuity models function most accurately when attached to lines that match their corresponding edges. Directly connecting discontinuity models to one another reduces their accuracy.

Reference

[1] K.C. Gupta "Computer-Aided Design of Microwave Circuits", Artech House1981 p.60

[2] A.A. Oliner, "Equivalent Circuits for Discontinuities in Balanced Strip Transmission Line" IRE Transactions on Microwave Theory and Techniques, March 1955 p.134-143

[3] H.M. Altschuler and A.A. Oliner, "Discontinuities in the Center Conductor of Symmetric Strip Transmission Line", IRE Transactions on Microwave Theory and Techniques, May 1960 p.328-339

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