I’ve got some RF traces in my layout that look like this:

Is there any way to calculate what the introduced inductance is of these lines?

Inductance (in a General sense) is a function of Wire/Trace length, cross-section-area…material properties, etc. Very typical/basic knowledge…

You’ll need to get the Trace Widths and Thickness and Length

You can Set and Get the Thickness from the PCB setup panel (physical stackup of Copper on desired layer(s)

You can get the Trace Lengths in several ways, from using the simple measurement tools in Kicad to using a Plugin… I don’t know about other plugins but here’s mine (if you’re brave)… Naturally, if you get that far, adding calculations in your code for the Inductance will be straight forward…

I understand that, but I’m asking about the additional curves added into the trace by the microwave tools. That’s a delta inductance above and beyond what you mentioned.

Is there a way to calculate the (in)effect of of these added curves?

Some EM simulation probably could. There are some inductance software which can calculate track inductances, too. But are you sure you need inductances, I see those kinds of tracks when KiCad tries to make two tracks of equal lengths.

I’m sure it’s fine.

I have a client who wants to hear proof that it is fine, beyond us saying “not a problem”.

I just need a back-of-the-envelope that shows that the inductance introduced by these super common phase-matching trace-lengthening procedures is negligible.

They’re 12GHz transmission lines.

For things at 12GHz I better be quiet. This could help. Coil32 - Online calculators But I think the idea is to get a differential pair with equal lenghts=inductances=delays.
Perhaps Googling “microstrip differential pair” could bring some ideas.
This looks interesting Differential Pair - an overview | ScienceDirect Topics

At 12 GHz you should be talking about impedance, not inductance.
Wavelength on a PCB is going to be just 20-25mm depending on Er, so these meanders are significant

Yes, you could. You can just google how to calculate the inductance. Maybe this site might help: What is Inductance - The Engineering Projects

…hum… Sure, I could be completely misunderstanding this but, is seems whether it’s Inductance or Impedance is not important to the question of:

So, I won’t belabor this beyond: You can calculate whatever you want based on the Length and/or Delta-Lengths…

Screenshot shows the Lentgh of a Trace and Length of trace section plus the additional curves from placing tuned trace

I’ll leave it there…

1 Like

Well, at least the client didn’t ask you to include capacitive coupling?

There are EM solvers that could import those tracks and calculate impedance, crosstalk etc like keysight ADS, Cadence AWR, but they are seriously expensive

… Following up…

Two Items:

1. I added Inductance Calculation (Calc’s, see image)
Gets the Track-Width from the PCB (set to 1.0 mm)
Uses a Hard-Coded Track-Thickness (0.035mm per Stackup panel)

2. Re: Track-Thickness.
I’m not finding Thickness in the Class Reference Documentation.
Thus, Thickness is hard-coded for now. I may add an Input-Dialog.

Does anyone know how to get the Stackup’s Track thickness
from code or from the User Scripting Console??

Note:
The plugin enables selecting Full Track and Individual segments (in any combination) - screenshot

Track With All Curves

Straight track

Selected Segments

Code Snippet

1 Like

This topic was automatically closed 90 days after the last reply. New replies are no longer allowed.