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Most filters I've come across aren't infinitely long. I don't think there's a way to simulate the scattering parameters of such a structure in HFSS, and I doubt the results would be particularly useful anyways.
Are you perhaps looking to obtain the structure's band profile (dispersion diagram)?
Actually, I am designing a sinusoidal corrugated waveguide (periodic structure) which has been assumed to be infinite and perfectly conducting in order to achieve filtering response. I have designed it to be more than 20 lambdas ( approximately achieve infinite waveguide) and I has assigned a perfect electric boundary on its walls as well as wave ports on the front and back faces. The results (S11) I have got demonstrate the filtering response. But there are some problems do not meet the mathematical derivation results which have been obtained in Matlab, such as a shift in the resonance frequency and the simulation does not work correctly for small delta (which is the corrugation amplitude). in overall, I am trying to find a solution for this problem, so I expect to be something in the boundary and wave port assignment. Could you help me to find a solution for this?
Assignment of master / slave boundaries is just a suggested solution to solve the problems I have faced. However, I have applied these boundaries on the waveguide, but the results are not correct. What do you suggest in order to solve these problems?
Please, refer to the attached files
The images you attached don't really tell anything about your HFSS setup.
If your scattering parameters are just slightly shifted, then I would suspect the convergence of the simulation. Try letting the solution do a few more adaptive passes and see if anything changes.
I have increased the adaptive passes 10 passes to ensure the convergence, but nothing changes. Please, refer to the attached HFSS file.
Kindly note that the resonance frequency which has to be centered at 3GH is shifted to the right. Also, note that when decreasing delta( corrugation amplitude)to be less than 0.1(for example to be 0.01), the simulation does not work correctly. What is your suggestion to solve these problems?
Your setup seems correct. It even does not break for me when delta is smaller than 0.1 (HFSS 17).
The simulation produces extremely low meshing, so I would stick with my initial guess that the simulation is not adequately converged. The problem in this case is that you are converging in the passband, where S11 is extremely low, and S21 is extremely high, which won't change much even if the mesh is not adequate, due to the bandwidth of the passband.
Set the maximum number of passes to at least 20, delta S is OK at 0.002, but minimum number of converged passes should be something like at least 10. You could also try converging at the top of the passband instead of the middle.
Probably a better solution is to specify a seed mesh, with minimum length equal to at least half the radius of the corrugations.
In fact, I have done all you mentioned, but nothing change. I have ensured of convergence and put a smaller seed mesh and nothing change. I do not expect that the problem is related to convergence. Is it possible that is related to optimization of the variables?
Scattering parameters measure the output voltages with respect to the input voltages. Obviously, for an infinitely long structure, there will be no output voltages.
The purpose of an eigenmode simulation is to tell you what modes the structure supports and what their properties are - nothing else.
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