Thank you for your reply Fiwi sir, i think you have simulated the results in CST MWS. Thickness of the patch and ground plane are not important IMO. Have you got the same return loss graph as depicted in the paper?
I am exciting the antenna with Waveport, is it necessary to excite the antenna with SMA connector, if so can you send the SMA connector design file in HFSS for cpw feeding.