pcb-rnd knowledge pool


Installing and using imp_setup

imp_setup by Tibor 'Igor2' Palinkas on 2020-06-07

Tags: howto, imp_setup, impedance, high, frequency, signal, integrity, stripline, microstrip, waveguide

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Abstract: The impedance setup script is a user script that provides a simple, graphical, interactive way to set up layer group properties and routing styles to ensure trace impedance on transmission lines (e.g. microstrip). This node is a mini-howto for setting up and using the script.


1. Installation

2. The dialog box

After loading the script the dialog box can be open by using the new menu plugins, script, "impedance setup...". The dialog box for microstrip looks like this:

It automatically picks up the line width from the currently selected routing style and the layer thicknesses from the default selected layer group pair, which is top copper and the first internal copper group by default.

2.1. layer group selection

On the left, the copper layer group pair can be selected. The first selector always refers to the layer group of the signal, the second is the substrate group sandwiched between the two copper groups and the third is always the ground "plane" copper group. Note: the orientation of the widgets don't always reflect the orientation of the board. The sw button swaps the copper groups. The signal layer group must be either the top or the bottom copper layer group.

When group selection is changed, the right side values are automatically filled in and if any checkbox is ticked, the selected field is recalculated.

Upon invalid group selection the substrate layer group is emptied and the group-related right side values are reset.

2.2. cross section view

The cross section view is not interactive, it is only for information on the meaning of the right side data fields.

2.3. Right side data fields

Field values are copied from layer group attributes and route style properties but can be edited by the user. If one of the checkboxes are checked, the value of that field is calculated from the others using an approximation formula.

Each field that is bound to a layer group attribute or route style property has a "set" button. When the user clicks the set button, the current value of the field is copied to board data:

The "set all" button behaves as if the user clicked on each set button.

3. Using the script

Now that the setup is done, drawing a microstrip line is easy:

The above setup ensures that: