Question about CST MWS boundary conditions?

[winsonwhy]

Hi friends,

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.

 

[winsonwhy]

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.

 

[oswaler]

Hi there,

Boundary conditions play a crucial role in simulations as they define how electromagnetic waves interact with the boundaries of the simulated structure. In CST MWS, the default boundary condition is set to "perfect electrical conductor" (PEC), which assumes that the boundaries are perfect conductors and there is no reflection or transmission of electromagnetic waves.

In your case, it is possible that the difference in S11 results is due to the boundary condition. The IEEE paper may have used a different boundary condition, or they may have taken into account the physical imperfections of the antenna (such as surface roughness or material properties) which can also affect the S11 curve.

Changing the boundary condition to "open" can help eliminate any warnings related to the PEC material touching the boundary, but it may not accurately represent the real-world behavior of the antenna. It is important to carefully consider the boundary conditions and their effects on the simulation results.

I would recommend checking the IEEE paper for any specific boundary conditions they have used and trying to replicate them in your simulation. It may also be helpful to consult with other experts in the field or the CST support team for further assistance. I hope this helps. Best of luck with your simulations!