stripline balun

Hi,
I have problem with port definition. I want to simulate this balun at end-to-end connection, so I need define two unbalanced port. When I have used differential ports,
results are very good. When I have applied ground port conversion to both negative ports, results are unreasonable and configuration of ports are automatically changed.
Thanks for any suggestion.
Hi

Hi, ondra:

Please don't use ground port. It is an old scheme and it may not be good. Please use differential port with + and - terminals. Regards.

Hi jian:

Thanks you for your answer. Finally, I reached good results