Simulating Two Wire Transmission Line (ladder line) in HFSS

[atemme]

I have been struggling with HFSS for the past few weeks trying to get this to work.

I would like to simulate a two-wire transmission line. For starters, I just want to have two conductors in air and want to know the input impedance. It would be nice if I could put either a load or another port at the far end of the transmission line.

Take for example TV ladder line: https://en.wikipedia.org/wiki/Twin-lead
300-ohm transmission line uses 20 or 22 gauge wire separated by 7.5mm. There is usually a plastic or insulator between the two wires.

My simulations right now are just 2 cylindrical conductors in an air box with radiation boundaries on the four sides. One end of the box is PEC to simulate a short between the lines. The other end is a port. I have tried using wave and lumped ports, terminals and differential pairs - all with no acceptable results.

My questions are:
-Is there an example of a two-wire transmission line for HFSS floating around? I can't seem to find one.
-How do I feed a two-wire transmission line in HFSS since the is a large spacing between the conductors?

Any help would be appreciated.

 

[PlanarMetamaterials]

Welcome atemme,

I don't have an example, but it sounds like you're off to a great start. What you want to do is place a waveport (in a driven modal simulation) on the edge of your air box that covers both of the wires' ends. To ensure that you are exciting the correct mode, draw an integration line between the two lines.

Be sure to look at the fields and check which mode is being excited. If the distance between the wires is large, HFSS may initially pick the incorrect modes. If this is the case, you can simply increase the number of modes that HFSS is solving for, and it should eventually get the correct one.