Why do i need periodic boundary conditions in order to calculate reflection. c?

Altair Forum User
Altair Forum User
Altair Employee
edited October 2020 in Community Q&A

Why do i need periodic boundary conditions in order to calculate reflection. coefficient? I dont have a periodic or infinite structure, i want to calculate it for cube. But when i run feko solver, it requests me to set some periodic boundary conditions. I dont get it.

I use a plane wave as a sourse. Should the plane position for phase reference be by (0,0,0)? (because it should be orthogonal to k propagation direction)

 

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Answers

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited February 2017

    Hello Bobo,

     

    the error that you should be seeing is:

    Reflection/transmission can only be computed for 2D periodic boundaries or planar Green's function

     

    This is a limitation on the Reflection/transmission request: either you must use periodic boundary conditions or the planar Green's function. However, it is does not support general 3D structures without either of these 2 options.

     

    Regards,

    Peter

  • JIF
    JIF
    Altair Employee
    edited February 2017

    Hello Bobo,

     

    I think there is a misunderstanding with respect to what you want to calculate vs. what you are requesting from FEKO.

    The TR (transmission reflection) coefficients are for calculating reflections from surfaces. That means that you either need to define a 2D periodic structure (PBC) or have an infinite ground definition in your model.

    What you are trying to calculate is probably monostatic or bistatic RCS, correct? To calculate that, you simply need a plane wave source and a far field request.

    If you are interested in the scattered near field, you can add near field requests to your model [it is possible to calculate either the total field (default) or just the scattered part].

     

    I hope this helps!

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited March 2017
    Altair Forum User said:

    thank you, it helped a lot. 

     

     

     

    Hello Bobo,

     

    I think there is a misunderstanding with respect to what you want to calculate vs. what you are requesting from FEKO.

    The TR (transmission reflection) coefficients are for calculating reflections from surfaces. That means that you either need to define a 2D periodic structure (PBC) or have an infinite ground definition in your model.

    What you are trying to calculate is probably monostatic or bistatic RCS, correct? To calculate that, you simply need a plane wave source and a far field request.

    If you are interested in the scattered near field, you can add near field requests to your model [it is possible to calculate either the total field (default) or just the scattered part].

     

    I hope this helps!

     

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