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Microstrip Gap on Multilayer Substrate (Static Solution): MMGAP



MMGAP models a gap in microstrip line on multilayered substrate GMSUB.



MMGAP$ is a Microstrip iCell and has no parameters. See “Intelligent Cells (iCells)” for more information.

Name Description Unit Type Default
ID Name Text TL#[1]
W Conductor Width Length W[2]
S Gap Width Length W[2]
NL Number of dielectric layer carrying conductors Scalar 1
GMSUB Substrate definition Text GMSUB1[3]

[1] # is automatically incremented as additional TL 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 GMSUB is present in the schematic, this substrate is automatically used. If multiple GMSUB substrate definitions are present, you must specify which to use.

Parameter Details

GMSUB.. Defines the stackup of dielectric layers. Any dielectric layer may carry a microstrip conductor on its top.

Parameter Restrictions and Recommendations

  1. GMSUB. Supplies parameters for the multilayer dielectric substrate: The number of layers Nlayer, conductor thickness T, conductor metal properties, the presence/absence of metallic cover, and the cover height above the substrate. The GMSUB Cover parameter allows the addition/elimination of an infinite metallic plate acting as a cover/shield. Setting the Gnd parameter to "Suspended substrate" allows elevation of the dielectric stack above the backing ground. The elevation gap is filled with air and the HB parameter specifies its height.

  2. The number of dielectric layer carrying conductors (NL) must comply with the rules of numbering GMSUB layers. Parameter NL sets the number of the dielectric layer (specified at GMSUB) that carries a gap conductor on top. If the GMSUB Cover parameter is set to "Metallic Cover" and the gap conductor is on top of the dielectric stack, then NL=1 (the dielectric layer just under the cover is not included in the count). If the GMSUB GND parameter is set to "Suspended Substrate" and the gap conductor is on the bottom of the dielectric stack, then NL=N+1, where N is the number of layers in the dielectric stack specified by the GMSUB N parameter.

  3. MMGAP does not use GMSUB parameter T.

Implementation Details

This model is represented by a symmetric π-circuit comprising two frequency-independent capacitances. The modeling solution is static because operational frequency is assumed to be low enough to allow capacitance approximation; dispersion and conductor thickness are not accounted for.


This element does not have a visual layout cell. The layout cell creates a gap between the two multilayer microstrip or stripline elements that connect to each side. The size of the gap is determined by the G parameter. Since there is no layer to draw, linetypes do not apply. You can select the layout cell to snap the microstrip or stripline elements to it.

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.

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