I made up a quick model to reflect the dimensions in the paper, but did not tune it carefully. A beginner will probably find that the process of tuning the mesh sizes for fewest meshcells vs most accurate results is the most laborious and sometimes hard to understand part of using a tool like CST. This is a difficult process for me because I don't understand all the variables but trial and error plus understanding what mesh sizes I really want seems to give a good result most times. Often, I find that the automatic mesh generator doesn't provide accurate results and I have to tune my mesh. The biggest trouble I usually get into with my models is inappropriate meshcell sizes. This would generate the smallest number of meshcells so the simulator would compute more quickly than with my method. When I load an example of a patch antenna provided by CST, I note that they just use Open as their boundary for five of the six planes, and place an electric (Et=0) boundary behind their pcb. As an antenna designer, I have typically used the boundary condition Open (Add Space) in order to insure that my nearest fields are not hitting the boundary as this seems to give me the best results. Other conditions do similar critical things, so it is very important to define the right boundary conditions. Obviously this would have a severe effect on the model. If you define the boundary to be an electric (Et=0) boundary, then this is effectively the same as placing a perfect ground plane on that boundary of the rectangle that contains your model.
If you specify OPEN, the simulator effectively places perfectly matched microwave absorber material at the boundary, which guarantees that this plane appears to be open space. The boundary condition defines the radiating environment of the model.
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