Hi,
It is really not clear what do you want to do.
If a radar uses a phased array antenna, we can not named it as a phased array radar.
In other word Using a phased array antenna in a traditional radar does not change it to a phased array radar. the capability of a phased array radar in search and track simultaneously is more desirable.
Therefore a phased array radar can not be simulated using HFSS Only and also an not be designed using this software.
Hope it helped.