Re: probe in hfss
First ; you have to decide about bandwidth and resonance frequency. dielectric permittivity effect on bandwidth and frequency. (air small banwidth etc.)
second you have to draw H shaped patch over dielectric and also assign it perfect E,
Ground plane should be assigned perfect E with infinite or finite ground plane option, (Also you need a cut on it for coax probe)
Dielectric box doesnt need assignment of perfect etc.
third; dielectric box height effects banwidth and also resonance frequency. Similiar condition exist on coax measures too. Cos impedance changes with dimensions.
good luck[/b]