Any advice for modeling impedance surfaces (for scattering problems) in HFSS?


We are trying to model a phased array antenna in HFSS using surface impedances in place of unit cells. We are getting strange results and are not able to determine what the issue is. We started by setting up a 4x4 array of square sheets. Then each is given an impedance boundary corresponding to a particular phase shift. This structure is then excited by an incident plane wave. We have had issues with the adaptive mesh not converging due to high fields on the sheets at certain frequencies. Also, the far field results we get from these studies do not match what we expect to see. We have not been able to find any helpful resources so far related to this issue. Does anyone have any advice on modeling surface impedances for scattering problems in HFSS? If any part of my explanation is unclear, please let me know and I can provide more details as well as a project file.

Thank you


  • rtkrtk Pune, IndiaForum Coordinator

    Hello @rbeneck,

    Could you please share the images of your model covering the place where you have given the impedance boundary and the plane wave excitation details?

    By this way we would be able to guide you properly.


  • You probably would need a floquet ports in driven modal, examine manuals.

    single cell can be examined in eigenmode indirectly, because it is an impedance with normal incidence, and periodic boundary gives you dispersion in tangential direction

  • Hello,

    Thanks for the quick response. I apologize that I'm late in getting back to you. I have attached screenshots of the model, the impedance boundaries, and the plane wave excitation. (Note that the variables for the impedance values are datasets that vary with frequency. I do not think this is the source of the issue).

    Also, here is a plot of the fields and the mesh on the surface at one of the higher frequencies. There are very high fields, so this leads to an overly dense mesh. We are confused why this is occurring. Do you have any thoughts about this?

    Thank You

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