Cross-talk between transmission lines and signal pads
I have a 7-layers PCB with the following layer stack-up: high voltage plates (1), segmented signal pads (2), ground shield traces (3), signal traces (4), ground shield traces (5), segmented signal pads (6), high voltage plates (7). The layer 4 (signal traces) is connected to layer 2 and 6 (segmented signal pads) with a via - see pictures attached - and is meant to extract a triangular current signal (1 ns rise time, ~300 ns decay time), induced on layers 2 or 6, outside of the PCB. There are several 'segmented' signal pads in layer 2 and 6, each connected to one single signal trace. I want to evaluate the cross talk due to the fact that the signal trace from a given segment run beneath other signal pad segments. The ground layers 3 and 5 are here to prevent this cross talk but they are traces, not plates and I want to see what width those shield traces should have to reach an acceptable level of cross-talk between a signal trace and the other signal pads.
I tried to use the cross-talk functionality within SIWave but it gives me 0 everywhere, I suspect it only considers cross-talk from trace to trace, not from pad to trace. I also tried to define ports and get the S-parameters but see an unexpected behavior: when I enlarge the width of the ground shields, the cross talk actually increases suggesting that the cross talk is actually occurring through the shields themselves (they all belong to the same net). Here are my questions:
1) Is SIWave the proper tool to do such a study or is there another one more suitable? Another possibility I see is to derive the equivalent circuit from Maxwell and then use Simplorer?
2) When I display the mesh in SIWave after solving the S-parameters, it seems to be defined only on a plane (and it is very coarse), even when checking the 'Q3D Solver' option. Can I force SIWave to solve things in three dimensions?
3) The ground shield traces are assigned to the 'power/GND' net list, is there something else to do in order to have SIWave considering these traces as perfectly grounded?
Thank you very much for any input!