CST-Connecting CPW and microstrip

Hi,

I want to connect a microstrip using Copper with a Roger's 3003 substrate to a CPW with Niobium as the center conductor and ground plane and a silicon substrate. I have connected them currently using bond pads, but does anyone have any suggestion for a better way to connect.

Also, when i specify the ground plane and center conductor as Niobium, CST automatically shorts them, is there some way to justify them separately.

I checked in the connection tree, and there is something called isolators. Are these components connected to nothing else.

All help will be appreciated.