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Microstrip Radial Stub Shunt (Closed Form): MSRSTUB2



MSRSTUB2 models a single microstrip radial stub that shunts microstrip line. This model is a two-port through element.



Name Description Unit Type Default
ID Name Text ST[1]
Ro Outer radius of the stub Length L[2]
W Conductor width Length W[2]
Wg Width of crossing of stub and microstrip line Length W[2]
Theta Angle of the stub Angle 90 Deg
MSUB Substrate definition Text MSUB[3]

[1] # is automatically incremented as additional ST element ID's are added to the schematic.

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

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

Parameter Restrictions and Recommendations

  1. Theta must be within the range 9 ≤ Theta ≤ 160.

  2. This model is feasible if


Implementation Details

Model implementation is based on cascading multiple segments of lossy microstrip transmission lines described in [1]. It accounts for losses in metal and in substrate dielectrics. Radiation loss is not included.


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

MSRSTUB2 replaces the MSRSTUB element, which is obsolete.


[1] B.C.Wadell, Transmission Line Design Book, Artech House, Boston-London, 1991, pp.306-307

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