Has anyone worked with differential signals in either of the simulation domains? I think the way to make it work in FEM is to create a waveguide port, and draw your impedance lines as 2 different modes (I think I saw this somewhere, but I don't remember where). I was also given a piece of code that converts these 4 port S-parameters to even & odd mode parameters, although I'm not sure where this came from. Is there something similar for the FDTD engine? It seems that when I have a pair of differential signals (two feeds) and I simulate in the time domain to look at the TDR, it is no different that if I were to make one port a feed and the other a passive component. This makes sense, since it only activates one feed at a time when it is simulation. Is there a way to declare two ports as differential signals, and have them simulate together?