CST - Shielded coplanar wave guide simulation error.

Hello,

i have been trying to simulate a shielded coplanar wave guide. I have however difficulties to implements ways to monitor the signal when it comes out of the structures. 
I have tried many different solutions:
-open (add space) boundaries in xMax and xmin. In this case the solver signaled that there were not enought transversals point in the wave guide port
-magnetic wall, following a tutorial made on a wave guide. This time i get "Waveguide monitor 2 is defined on a global boundary. This is not supported by the transient solver."

I don't really know how to solve the problems, and i'd be happy with any suggestion leading to the resolution them.

Thanks.

CST Studio Suite ​​​​​​​