HFSS - Two H Symmetry planes and one port less

Hi everybody,

I have a structure with two H-symmetry planes (the black lines in the pitcure), like a square cavity resonator (two ports device, see picture)

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To reduce the CPU-time computation, I can draw only a quarte of the resonator (highlited in red) and thus only of the two ports.


In this case, how should I evaluate the insertion loss of my cavity (i.e. a S21), having just the return loss of my reduced size structure?

Where could I add another dummy port to obtain the insertion loss?

Thanks

Francesco

Any ideas?
Do you think it is possibile to calculate the insertion loss of the whole model, just using a quarter of it?
Where should I put the second port?