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Microstrip Lange Coupler (Closed Form): MLANG



MLANG models the multiline interdigital Lange coupler based on N edge-coupled microstrip lines (closed form technique). MLANG features an improved layout cell and can be used in conjunction with LMAN (Lange Coupler Manifold).


Name Description Unit Type Default
ID Name Text TL1
N Number of fingers   4
W Finger width Length W[1]
S Width of gap between fingers Length W[1]
L Finger length Length L[1]
MSUB Substrate definition Text MSUB[2]
Gap Gap between open end of shortened finger and manifold (layout parameter only) Length 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 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 Details

N. Number of fingers

W. Width of the fingers (the widths of all the fingers must be the same).

S. Width of gaps between the fingers ( must be identical).

Parameter Restrictions and Recommendations

  1. This model is most accurate in the following ranges (where H is the substrate thickness and ε is the substrate dielectric constant):




    Outside these ranges, the accuracy degrades gracefully, and the results may still be useful, so no error message is displayed if these limits are exceeded. Do not use this model for two-strip couplers; use MCLIN or M2CLIN instead.

  2. The Gap parameter defines the distance between the open end of a shortened finger and the edge of the manifold (see the "Topology" section of MLANGE2). This parameter has no effect on the electrical characteristics of MLANG. You can set the Gap value in the Layout View only. To set the Gap, right-click the MLANG shape, choose Shape Properties to display the Cell Options dialog box, then click the Parameters tab. Set the Gap to the desired value.

Implementation Details

MLANG uses closed form representation from [2] and formulations for odd/even impedances of coupled microstrip lines from [1].

This is a lossless element, dispersion is included.

Note that the MLANG symbol has terminal numbering that differs from those of the obsolete element MLANGE, namely terminal numbers 3 and 4 are swapped. This numbering matches terminal numbering of the MLANGE2 element. If terminal 1 is input, then 2 is coupled, 3 is isolated, and 4 is direct.


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

MLANG can be used in conjunction with the LMAN element, which provides a layout intended to match the MLANG layout.


[1] M. Kirschning, R. Jansen, "Accurate Wide-Range Design Equations for the Frequency-Dependent Characteristics of Parallel Coupled Microstrip Lines", IEEE Trans. Microwave Theory Tech., vol. MTT-32, 1984, p. 83-90.

[2] D. Kajfez, Z. Paunovic, S. Pavlin, "Simplified Design of Lange Coupler", IEEE Trans. Microwave Theory Tech., vol. MTT-26, 1978, pp. 806-808.

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