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modeling finite structures

Posted Apr 18, 2011, 4:25 a.m. EDT RF & Microwave Engineering, Geometry Version 3.5a 3 Replies

Giuseppe Pirruccio
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Dear all,

I am trying to simulate a 2D-finite structure invested by a plane wave impinging at different angles. So far I have worked with the same structure but using periodic boundary conditions (Floquet) and the result is very good. Now i want to move to the real finite geometry and so I have placed PMLs around the structure, but I see some reflection somewhere and the shape of the wavefront is not good. It seems to start to be absorbed even outside the PML domain.

In particular I have set the absorption of the PML along x axis for the left and right PML , and along y for PML on the bottom . I have placed also PML on the corner of the box using absorption both in x and y directions.
The excitation comes from the top boundary through a port.

My question is of basically important i order to complicate further the model.

If it can be helpful I can apload the model.

In advance, many thanks.

Giuseppe
3 Replies Last Post Apr 18, 2011, 3:32 p.m. EDT
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Apr 18, 2011, 7:35 a.m. EDT
Hi

PML are normally for the same air or material as the surrounding one so you have sometimes spouradic "reflections" from material change between regions touching the PML (if that is the case of your model) and I^m not sure exactly how to avoid that. There a re a few threads on the FORUM, try a search

--
Good luck
Ivar
Hi PML are normally for the same air or material as the surrounding one so you have sometimes spouradic "reflections" from material change between regions touching the PML (if that is the case of your model) and I^m not sure exactly how to avoid that. There a re a few threads on the FORUM, try a search -- Good luck Ivar
Giuseppe Pirruccio
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Posted: 1 decade ago Apr 18, 2011, 7:39 a.m. EDT
Hi Ivar,

thank you for the wquick answer, unfortunately i knew that the change iof amterial could be a problem, so I set the refractive index equal to 1 for all the domains, but I still see something strange.

I will upload the model if you want to see it.

Giuseppe
Hi Ivar, thank you for the wquick answer, unfortunately i knew that the change iof amterial could be a problem, so I set the refractive index equal to 1 for all the domains, but I still see something strange. I will upload the model if you want to see it. Giuseppe

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Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Apr 18, 2011, 3:32 p.m. EDT
Hi

I find it looks quite normal !? you have some diffraction from the limited size of your scattering port aperture, and revealed by the 45 ° incidence. As you have no periodic conditions on the lateral side, I find this rather normal. It results in small oscillations of the field, but I see nothing astonishing, but I haven't seen your other calculations ;)

--
Good luck
Ivar
Hi I find it looks quite normal !? you have some diffraction from the limited size of your scattering port aperture, and revealed by the 45 ° incidence. As you have no periodic conditions on the lateral side, I find this rather normal. It results in small oscillations of the field, but I see nothing astonishing, but I haven't seen your other calculations ;) -- Good luck Ivar

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