How to define the excitation port of a differential CPW line in HFSS?

[Johnathan2023]

hello all,
Seems to be a basic question, but I am still wondering about it.
I'm going to get crosstalk in differential CPW line. And I have drawn a GSSG model as shown in Fig.1. However, I am confused about how to define the excitation port.
1）I know how to define a wave port, but I do not know how to view crosstalk.
2）I know that using lumped ports can view crosstalk through S31 and S41, but I do not know how to define the port excitation，Which one is correct - Fig.2 or Fig.3 or Fig.4? Or neither?
thanks.

 

[PlanarMetamaterials]

Welcome, Johnathan2023.

None of these are best. Using a driven terminal simulation, draw a single sheet on each side of your structure (y = 0 and y = length) that covers all lines (at least a significant portion of the side grounds). Assign terminals to your two signal lines, and you should be good to go.

If your conductor backing is supposed to be equipotential with the side grounds, I would recommend drawing in a metallic connection at the ports. This ensures the proper modes are excited.

Good luck!

 

[Johnathan2023]

Welcome, Johnathan2023.

None of these are best. Using a driven terminal simulation, draw a single sheet on each side of your structure (y = 0 and y = length) that covers all lines (at least a significant portion of the side grounds). Assign terminals to your two signal lines, and you should be good to go.

If your conductor backing is supposed to be equipotential with the side grounds, I would recommend drawing in a metallic connection at the ports. This ensures the proper modes are excited.

Good luck!

Hi, PlanarMetamaterials.

Your suggestions really helps a lot. However, there are other problems that I don't know how to solve.

1. I'm interested in the crosstalk between differential traces, but how can I find it in HFSS? Can you give me some ideas?

2. How can I draw a metallic connection at the ports? Do I need to draw some vias? Or "Unite" side ground and backing ground? Or "draw rectangle" coplanar with the port? I'm confused about it.

Thanks a lot .

 

[PlanarMetamaterials]

1. I'm interested in the crosstalk between differential traces, but how can I find it in HFSS? Can you give me some ideas?

I'm not sure how this is typically evaluated. I would think scattering parameters from the input on one line to the output on the other (e.g., S2:1,1:2) would be a decent metric to begin with.

2. How can I draw a metallic connection at the ports? Do I need to draw some vias? Or "Unite" side ground and backing ground? Or "draw rectangle" coplanar with the port? I'm confused about it.

Yes I typically draw some vias and unite all touching metallic objects.