Noticed issues in Ansoft Q3D's 2D Extractor

Hi,

I have noticed some issues in Ansoft Q3D's 2D Extractor and thought I'll put it up to see if others noticed something similar. Here's the situation:

I am trying to extract RLGC parameters of a transmission line for different substrate properties like loss tangent and substrate conductivity. For a constant loss tangent, increasing substrate conductivity should result in higher values of 'G'. However, the extracted 'G' values are exactly the same regardless of substrate conductivity. After some debugging, I found that Ansoft Q3D's 2D extractor 'ignores' substrate conductivity if loss tangent is defined.

To fix this problem, I extracted 'G' in two steps: (1) GL - when only loss tangent is present, (2) GC - when only substrate conductivity is present, and added the 'G' values as GL+GC. The results are very close to that predicted by Sonnet. This is most likely a bug in the software!

Let me know your thoughts/comments.

Thanks.