Need help with CST studio.

[DOS]

Hi all I am new to CST Studio suite. I am trying to implement antenna design provided in the research paper, but I am unable to get the results as specified in the paper. I need to find out what are the mistakes I have done during the design. Please guide me for the same.
I am attaching the CST files for the figure (2) from the paper.
Thanks in advance

 

[vfone]

At first view I see that you are using FR4 substrate with permitivity 4.3 and loss tangent 0.025, when in the IEEE document they use permitivity 4.4 and loss tangent 0.018.
May not be a big difference, but your results are not very far from the paper results. On S11 plots you have a bit of frequency shift and less return loss. With one exception (b), you have always S11 better than -10dB.
Otherwise I am not a big fan using PIN diodes to switch antenna elements to get multi-band operation.