Hi all,
How is one to define two net classes for a single trace? I have to create a test trace for a 100-Ohm differential pair, but the signal is launched into the traces through 50-Ohm connectors, so one segment of the trace should be 50 Ohms single ended, while another is supposed to be 100 Ohms differential. This means that both the trace widths and the clearances change along the trace.
Is it possible to do this in a clean way, or does this require some sort of hacking?
Hi, I think that you will need to split your net in two using a NetTie.
It’s a symbol (and associated footprint), to connect 2 nets together, so one net can be on 50 ohm class, and the other one on the 100 ohm class.
Yes, that’s pretty close, thanks for the suggestion! My only difficulty with that is that the net tie is a multi-port, so I can’t really have a continuous trace with its segments connected to different nets. I could, perhaps, create a custom footprint, and work with that.
Seems simple enough to use the NetTie’s in Kicad with the defaut Footprints… Both THT and SMD shown below.
50Ω and 100Ω coming in and Tied(or whatever you want to name it) going out
Well, at 10 GHz you can’t really use the default footprint… But I took one of them, and modified it such that it matches.
What you have in a screenshot is actually splitting the signal. I needed only a pair of two-ports, for the two traces of the 100-Ohm differential signal go into a pair of 50-Ohm single-ended connectors.
