I was at a loose end and decided to see just how far I could push LibrePCB to produce a transmission line. Ok eventually there will be a tool for this but I thought I would share my fiddle findings.
This is what I did:
I created new categories for Components and Packages. I created a schematic symbol called transmission line. Basically a two port device with slightly thicker lines to represent the transmission line. No problem here. I next created a Component. No real issue here either but I thought is would be really useful to create some Attributes. Impedance (use Resistance units), Line Length, Line Width, Spacing etc. (are, no Unit support for mm), Number of wiggles :) (o'fiddle, no integer support). [I think it would be a useful improvement to support a wider set of attribute units. Anyone else have any thoughts?] I created three transmission lines in Packages. Parallel and "zig zag" wasn't to difficult but "wiggle" failed to create parallel curves (more work needed). Also if it was possible for the Polygon Tool to support parameters and equations then the Attributes mentioned earlier could be used to drive the transmission line generation. I didn't try to produce any specific Impedance in this experiment. Creating Device was no problem. Placing and routing the transmission line was no real issue but I only conducted a crude test. I did note that if a plane was placed over the transmission line then it was not cleared, it did not recognise the trace lines of the transmission line. I can for see that to optimise the length with out any parasitisation support means a back an forth to the library editor.