UWB antenna as filter

Hi,

I am interested about planar UWB antennas like vivaldi or patch antenna.
These UWB antenna should be considered as what type of filter (eg FIR or IIR) ?

After simulating in HFSS, if I save |S11 | dB 2D plot in .csv format, how may I get frequency response H(jomega) from S11.csv file in MATLAB?

Import .csv to MATLAB
https://www.youtube.com/watch?v=edYlhNdDCqE