cylindrical resonator cavity with coaxial cable

Hi!
Can anybody help me making in Comsol a cylindrical resonator cavity with coaxial cable as feed with a little extension of inner conductor to couple energy inside the cavity? I’ve tried to make it with no luck because S11 parameters give to me wierds values. The parameters of the cavity should be:
- Cavity has air inside and PEC as boundary;
- cavity has a 120 mm radius and 251 width because should be designed by considering fondamental TE mode;
- frequency range between1.45 and 1.65[GHz].

Thanks