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Cylindrical One Port Via with Microstrip Pad (Closed Form): MVIA1P



MVIA1P models a microstrip short at the end of a transmission line. It is an aggregate model comprised of a transmission line and a transmission line open-end effect, with a via to ground at the junction of the two transmission line elements. The result is a square pad with a via in the middle.

Equivalent Circuit


Name Description Unit Type Default
ID Element ID   V1
D Hole diameter um 40
H Substrate thickness Length LPF default
T Metal thickness Length LPF default
W Pad width Length LPF default
RHO Metal bulk resistivity normalized to gold   1
*SNAME Structure name from LPF file, empty string uses VIA, DEFINE, BEGIN from LPF file.    
MSUB Substrate definition    

* indicates a secondary parameter

Parameter Restrictions and Recommendations

Parameter W should match the width of the transmission line connected to MVIA1P. Otherwise, you can use any of the MSTEP family of junctions to model the change in line width.

Implementation Details

MVIA1P is implemented as a series combination of MLIN and MLEF, with VIA1P at the transmission line junction.


VIA models draw according to the SNAME parameter setting on the via, as configured in the LPF. If this parameter is left blank the via definition in the LPF is used to define the via layers. See “Via Definitions” for details. This typically works well if there is only one via type in the design. If you need to have different via layers, the best approach is to create structures in the LPF for each type, then set the SNAME parameter to match the structure name in the LPF. See “Structure Type Definitions” for more information.

Recommendations for Use

When using this model, keep in mind the physical nature of the square pad surrounding the via. You will effectively add a length to the targeted transmission line equal to W/2, which is the distance the signal sees in the MVIA1P before encountering the via. The element connected to MVIA1P should, therefore, be shortened by W/2 if electrical length is critical.

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