spiral microstrip antenna with finite ground plane

[chitra takle]

hii,
i am working in HFSS v.10 and i am designing a spiral microstrip antenna with finite ground plane. However, i am getting most of the radiation below ground plane. Please help me detecting the problem with my design. i knw i can use finite ground plane but its impractical. i have to fabricate this antenna. so every dimension should be finite. no using sheets which has zero thickness coz again its impractical please help its urgent. thank you in advance.

 

[khaled.ayman]

Can you try playing around with your radiation box? The height should be minimun lambda/4. Not really sure if this will improve the results.