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Cylindrical One Port Via with Stripline Pad (Closed Form): SVIA1P

Symbol

Summary

SVIA1P models a stripline 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 two vias to ground at the junction of the two transmission line elements (one via up to the upper ground and one via down to the lower ground). The result is a square pad with a via in the middle.

Equivalent Circuit

Parameters

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.    
SSUB Substrate definition    

* indicates a secondary parameter

Parameter Restrictions and Recommendations

  • Parameter W should match the width of the transmission line connected to SVIA1P. Otherwise, you can use any of the SSTEP family of junctions to model the change in line width.

  • Parameter H should be set to the substrate's B/2, since each via only goes through half the ground-ground spacing.

Implementation Details

SVIA1P is implemented as a series combination of SLIN and SLEF, with two VIA1P's at the transmission line junction.

Layout

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 SVIA1P before encountering the via. The element connected to SVIA1P should, therefore, be shortened by W/2 if electrical length is critical.

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