Hi Himson,
I have always liked LPD antennas.
They are not particularly difficult to design or build. I find LPD design Handbook by Smith a particularly useful reference. Design guidance is readily available in the usual places (antenna books, IEEE, the web among others).
As a general guide the longest element is slightly longer than a half wavelength while the shortest elements are on the order of a quarter wavelength. the more pointed the antenna the higher the gain. From 6 dBi to around 12 dBi gain is easily achieved. There are a number of "optimum" design curves around for your reference. Note that there is a slight gain error in some of the versions but as you are going to simulate the antenna that will not present a problem.
HFSS will do fine with a simulation, particularly as you can model the feed detail as well. It will work fine provided you have enough RAM. I modeled an LPD about a year ago and it worked fine. As I recall it was a 1 to 12 GHz design and s11 came out to be on the order of -15 dB.
MI Technologies (it is no longer featured on their webpage and they ask that you contact them directly with questions) has a LPD in a band you may find useful and another may be found here: h**p://www.ets-lindgren.com/page/?i=3144
(??? I replied to what I thought was this thread elsewhere on this site .... maybe it was posted twice. apologies if this is redundant ....... )
Regards,
Azulykit