emfemc
Newbie level 1
I simulated s parameters of a two-port PEC wave guiding structure. I tried four different cases:
case 1: Wave ports were used. Results OK.
Case 2: I used PEC 'cap' to cover the ports, and used wave ports. Results OK.
Case 3: The whole structure was put into an large air box. I used lump ports. Results NOT OK.
Case 4: The whole structure was put into an large air box. I used PEC 'cap' to cover the port, and used wave port. Results similar to case 3, NOT OK.
It is very strange if compare Case 2 and Case 4. For both cases, the whole structure actually is wrapped by PEC boundary. So in case 4, there is no interaction of the internal field of the structure with the air outside. So the results of Case 4 should be the same as Case 2. But it is not!
Why the results are different when the structure is put into an air box?
case 1: Wave ports were used. Results OK.
Case 2: I used PEC 'cap' to cover the ports, and used wave ports. Results OK.
Case 3: The whole structure was put into an large air box. I used lump ports. Results NOT OK.
Case 4: The whole structure was put into an large air box. I used PEC 'cap' to cover the port, and used wave port. Results similar to case 3, NOT OK.
It is very strange if compare Case 2 and Case 4. For both cases, the whole structure actually is wrapped by PEC boundary. So in case 4, there is no interaction of the internal field of the structure with the air outside. So the results of Case 4 should be the same as Case 2. But it is not!
Why the results are different when the structure is put into an air box?