I have not used ADS and HFSS for my designing. I have heard of ADS though and some of my friends toldme that HFSS is the one which can help u simulate antenna.
Can u tell me how to exactly layout the PCB antenna (21.5 *23.5 mm) on ADS and extract the inductance and radiation resistance.
22 mm by 23 mm implies an electrically small antenna. I suspect you will want to use "radiation boundaries" to simulate free space.
You will essentially build a 3D image of your antenna as you enter the software. You can easily extract s parameters and far field radation characteristics. If you really need inductance and radiation resistance I suggest you spend some time with the on-line help and alternately the tech support folks to see how that would best be extracted.
It looks like you are going to have the opportunity to learn about antenna design.