patch antenna design cst

Hi all;
please can somone help me to design the patch antenna by using CST?
i simulate some patch antennas but i dont obtain the same results (S11). also the difference with the results obtained by simulating the same antenna with HFSS is > more than 1GHz. what is the source of this problem: excitation, boundary...or others?
thank you.

well i am not sure of your problem......as i havent seen your design.....but there must be some problem with your excitation and the air box......wel i have just recently designed a patch antenna of 1.6 GHz that operates quit much precisely.....
but the thing is that when you calculate the lenth and width of patch for a certain frequency you wont be getting the desired result in simulation as it was me too the same problem in HFSS ....so you then will have to make a hit and trial method to get the desired results......by adjusting the size of patch by yourself and that of the microstrip line as well......so try this method and then let me know by varying it to diffenrent sizes from the calculations.....and what materials are you using for your design......roger is the best but if you use fr4 you wil have a wider band width.....and for the patch and ground use pec(perfect electric conductor).....and for the radiation box use air.....and dont assign it any boundry as it is air and dooesnt need any.......and also assign excitation to the port after you draw the air.....

Thank you very much dear arsi15,
Attached to this post you'll receive CST project of one tri-band printed antenna, already published. i'm working to re simulate this antenna by using CST, but i have not obtained the same results of this aticle (all bands are shifted on the left). on the other hand i simulate this antenna by using HFSS V.9.2, but also i have not obtaine the article's results (bands shifted on the right).
please, can retry this simulation (please i use CST version 5) or (HFSS V.9.2) and help me to reduce resolve this problem.
thank you very much.