Design of cylindrical wavegudie aperature within a plane with radome

Hello, I need some help in HFSS antenna design.

For my project, I should design antenna with cyrcular weave gudie with aperature within a plane, and I should simulate it with paper radome.

Radome is used for ajdustment of minimal reflection.

Antenna is having a probe feeding of lambda/4 (4.15 cm). Plane dimensions are 45x42.5x1cm, cylinder: height 17,.15cm, radius 6cm

I've designed the antenna with these specs and with probe feeding and i made a paper radome.

Im not having a expected S11 diagram, so if someone knows where is the problem, or what I'm doing wrong, I would appreciate any help.

Thanks.

P.S.: Im sorry if description is bad.

Attachments
1. S11 expected diagram
2. HFSS antenna design
3. Realistic antenna model