Simulation Problem in CST Microwave Studio

Hi everybody,

I'm new to CST microwave studio. Just finish constructed a structure of an L-probe patch antenna (from IEEE paper) and just run the simulation by transient time solver, the curve of the return loss(S11) against frequency that i get is different from what showing on the IEEE paper, so is it the boundary condition setting will affect the simulation results? And actually what is the function of setting the boundary condition?

During the simulation, a warning message "some PEC material is touching the boundary" was show. After change the boundary condition setting to "open(add space)" then the warning will eliminate when run again the simulation. But the s11 curve still different from the "actual" results.

Anybody can help?
Any comments will be appreciate.

Thanks.

Finally obtain the results same as the actual results by using CST 2006, still not sure why i can't get the correct results in 2009 version may be the new version's setting is a bit different. Regarding the boundary condition, with all boundary set to "open (add space)" and "et = 0" for ground plane i was able to get the correct results in CST 2006, so i think this setting might correct as well. I think the open (add space) will simply means that it is infinite boundary beside to all dimensions of the antenna so that all EM wave will propagate out without any reflection back to the antenna.