Can I check if the coax feeding an antenna is radiating using HFSS?

I'm trying to study a colinear antenna in HFSS. This is fed at the bottom. Obviously, unless completely balanced the coax will radiate, but I'd like to try to determine how good/bad this is and whether changes made improve or worsten this problem. To me at least, putting ferrite beads on the feeder does not really solve the problem, as you solve one problem (coax radiating), only to push the radiation to the antenna in a way which you can't define. So it screws up the radiation pattern in an undefined way.

There must be something one can do in HFSS to quantify this, but I don't know how to.

I've never tried looking at near field in HFSS. Would there be any point in looking at the fields close to the coax?

Any help appreciated, as I'm a bit stuck.

Deborah