Far Field Results In HFSS

hello,
I'm doing simulations using Ansoft's HFSS commercial software, and when i assign a Ex and Ky to my designed model there is a problem occur that i cant obtain Far field Results for that but as i removed the conditions that Removed Ex and Ky then i can easily obtain Far Field Results...can anyone pleae help me to sort out the isuue?
Regards;

One needs to specify Ex and Ky for a plane wave as in a scattering calculation.

One specifies the radiation boundary for a far-field calculation.

What is your calculation?

i have to calculate the the both scattering calculation and far field results both but i do the required steps but not able to obtain Far field results..
what i supposed to obtain the required results/