Need Help with Differential Pair Excitation in HFSS

Hello Everyone,

I am trying to simulate a multilayer structure in HFSS 13.0. It is made up of copper planes (PCBs) at the top and bottom and 5 layers of different dielectric materials in between. There are two pairs of cylindrical slots one at the top and one at the bottom, through which differential excitation is to be provided. The differential pair needs to have an impedance of 100 ohm (differential).

I am using driven terminal solution type and using lumped ports for excitation. Please let me know how exactly should I provide the excitation. I tried connecting a 2D rectangular sheet between the cylindrical slots at the top and bottom but it gives me a port refinement error on simulation.

Please Help Urgently.

Thanks!