Hello Marin,
First off, have you tried upping the maxiumum frequency of the TDR simulation in SIwave? If you have left it with the defaul maximum of 5GHz, I'm concerned that this ringing is above what SIwave is providing Circuit in the s-parameters.
Yes, I also have some concern about causality here. Are you using the default state-space method in Circuit, or convolution. If you run the casuality check on these s-parameters in the Network Data Explorer, what are those results?
You are navigating away from the AIS Discovery experience