Help me get S11 and S12 stable in this unit cell design in CST

Dear all,
Attached is unit cell . I have simulated in CST and also attached it.
The results seems to be incorrect since S11 and S21 have alot of ripples
I need you help just to get S11 and S21 stable
Thanks in advance

there is no one can help me to know what is the problem coz I'm new in CST

Hi,
I have the same problem
I am trying to simulate SRR but I have problem to define the air box
I will check your file and comeback to you

Hi mordakhay,
Is it possible for you to upload the results you are looking for? Is this unit cell is from a paper? If yes, please provide the name.
Regards