Learning Forum

[Sylvie Rana]

I am trying to simulate a completely PEC backed reflective metasurface with finite number of unit cells. I used incident plane wave (travelling at -z direction) to excite my finite array, which is located in x-y plane. I happen to get most prominent reflection from the back side of the PEC(i.e., along -z direction). However, I expect my reflections from the metasurface only along +z direction/ along some desired direction, as I have PEC at z=0.

I tried using Open boundaries and FE-BI region for the metasurface with no luck. I also tried illuminating the surface with a horn, where both horn and metasurface were surrounded by FE-BI region. All produced erronious huge backlobe from the metasurface PEC backed ground layer.

kindly suggest how to simulate this situation.

[Praneeth]

Hi Sylvie,

Thank you for reaching out to the Ansys learning forum.

Thanks for the elaborate description, but it is confusing. 

Please provide the following details to help us serve you better -

1. Is the top surface of your metasurface is facing the -ve Z axis from where the plane is incident?
2. May I know why you are using incident wave excitation? It is not possible to plot S-parameters if you use incident wave excitation.
3. May I know why you are trying to plot the radiation pattern of the E-field for this metasurface?

Kindly share the screenshots of boundaries, excitations and any other simulation setup in your model that could help to resolve your issue.

If you are new to simulating the metasurface simulation then I would suggest you to go through the split ring resonator example model available under the "open examples" option (Examples>HFSS>Metamaterial).

Best regards,
Praneeth.

[Sylvie Rana]

Hello,

 

Thank you for your reply. I will try my best to describe my problem.

 

I am trying to simulate a metamaterial based reflector, with an aim to be used for future RIS applications. My design is intended to reflect the incoming plane wave (for now I am simulating for normal incidence) to a specified desired direction towards a target presumably located at the far field distance. In this context, I would like to answer your questions:

 

No, the top surface of the metasurface is facing the +ve Z-direction, and the ground plane(pec) located at Z=0. I have applied the incident plane wave from a height of 20*lambda (this is required for my problem) from the top surface of the metasurface, directly above the middle of the metasurface. The plane wave has a k vector of -1 (minus one), so that it can travel in the -ve Z direction and illuminate the metasurface top layer. The metasurface is situated on x-y plane.

I am using plane wave incidence for my metasurface having finite number of unit cells, as I assume that the metasurface is going to be illuminated by plane wave (in my problem statement this is expected)  radiated from an antenna (say horn), situated a far field distance.

Thus, I am not expecting S-paramters right now. Rather, I would like to get the far field scattering pattern from the metasurface due to plane wave illumination.

I didnt get any other option to get the correct radiation pattern at my desired direction. I tried plotting the bistatic RCS too, besides rE plot, which gives me the same kind of scattering pattern. Kindly suggest me what else can give me the correct scattering pattern for the given problem. My main goal is to get most scattering at the desired direction for now. However, I might need to get the amount of power recieved at the target end (scattered power from the RIS), once I achieve the correct scattering pattern at desired direction, with scattered power at unwanted directions reduced as far as possible.

 

 

I have successfully simulated the unit cell of the finite array metasurface in my design with Floquet ports and Master/Slave boundaries, and obtained the desired characteristics. Hopefully, I am fine with this portion of my work. 

Ansys Images

 

[Saiful Islam]

Did you solve the problem?

[Sylvie Rana]

Yes. the back PEC needs to be out of your boundary. 

[Praneeth]

Hi Sylvie,

Thank you for sharing the fix to your issue.

There should not be any air gaps between the surrounding walls along the edges of the model. Did you get rid of this gap or did you only increase the dimensions of PEC backing so that the PEC edges protrude out of the surrounding wall?

I could not respond to your previous reply in time but it's great that you were able to find a fix yourself.

Best regards,
Praneeth.

[Saiful Islam]

Hello, I have assigned ground PEC as infinity, however, the radiation pattern didn't change at all, and it has a backlobe. then extended the ground plane out of the boundary, but couldn't solve the problem. same issue. please can you elaborate on the technique and how you solved it?

[Praneeth]

Hi Saiful,

Please share more details on your query to help us serve you better like screenshots of the model, error messages and other details to troubleshoot the issue. 

Best regards,
Praneeth.