size of port in hfss

hi
how can i find the exact and proper size of lumped port excitation in hfss?
i want to excite a dipole antenna in aboat 12GHz and i find out size of lumped port has a significant effect on results?is there any formula or consideration?
can anyone help me?
thanks alot

Hi:
As far as I know, the size of the lumped port is not important unless you want to see the input impedance.
I am not sure, but you can try by varying the size of the lumped port and consider the frequency response.