antenna impedance with hfss or cst

I've designed a microstrip antenna with hfss.
How can I see the antenna impedance with hfss or cst?
thanks

for HFSS,
you may choose "Result"--"Creat Modal Solution Data Report"--"Smith Chart" and get impedance in "S parameter" curve.
Also, you may choose "Result"--"Creat Modal Solution Data Report"--"Rectangular Plot" and get impedance in "Z Parameter"--"Im(Z(1,1))" and "Re(Z(1,1)).

I want see input impedance antenna.
How can I see the input impedance with hfss or cst or ..?
I have one microstrip antenna with 50 ohm input impedance.
How can I design the length and width of the antenna?
plz help me

In HFSS you can use Result"--"Creat Modal Solution Data Report"--"Data Table" and select "Z Parameter" and function "None"
In CST you can set marker points on the smith chart to get the impedance value or you can use the real and imaginary plots