Grounding bridges for CPW in Designer.

[ananth]

Hello Everyone,
I'm trying to make a CPW structure in Ansoft designer (Planar EM) and thus I need bridges for connecting the two grounds.
The slot layer is defined as a metallized signal layer. When I try to define a signal layer on top of this slot layer as the starting layer for a via, designer says metallized signal layer and signal layer cannot touch.
Does anybody know how this can be done in Designer?
Thanks a lot,
Ananth.

 

[dr_em]

If I remember correctly, vias are permitted only between similar layer types, no mix & matching. You're wasting your time with one anyway. Ansoft Designer's planar EM tool (Ensemble) doesn't handle CPW very well. I tried to model a finite ground CPW but I couldn't assign the ports properly as the software only lets you choose two edges to define a coupled port. I tried getting around this by drawing the three metals on a normal signal layer, attaching six regular ports, and taking the results back into the circuit simulator where I tied the ground plane ports to each other and set them as reference ports for the signal ports, hoping this would mimic the push-pull excitation. Unfortunately, it didn't give the proper results. The slots in an infinite ground plane (Ensemble's way of modeling CPW) is a good idea from computational resource perspective (meshing only occurs in the slots) but are not for practical use. Use Ensemble for other types of transmission lines and stick with Agilent's Momentum or Sonnet for CPW.

Good luck!