Learning Forum

[kaleor]

Hello,

I am working with a rather large Floquet simulation (90 x 100 cm at 1.25 GHz). I discovered that I can only include 100 Floquet modes max in the Floquet Port dialogue window. I would like to include many more modes in my simulation (perhaps up to 200 total), so I am curious as to why there is a limit on this. Is it because of memory requirements? Does the solution start to become unstable with more modes than 100 or so? I have attached a screenshot of my simulation below.

[Praneeth]

There is not certain limit on the number of modes supported in Floquet port.
May I know the specific reasons behind why you would like to look at 200 modes?
All the very best.

[kaleor]

Thank you for the response pmunaga!
I do not necessarily want to look at 200 modes exactly, I just know that I probably need a lot more modes than 100 to do what I would like to do. I would like more than 100 modes because I want to calculate the backscatter from a somewhat periodic 2D array of metallic patches. Because of the periodic boundaries I use, energy will only be scattered off the infinite surface (because of the periodic boundaries) in certain directions, or Bragg modes. If I want a Bragg mode in the backscatter direction, then I need to change the size of the unit cell in order to accommodate that. Having a large unit cell (or many Bragg modes) means that I do not need to change the unit cell size as much, relatively speaking.
I am using HFSS in ANSYS Electronics Desktop 2020 R2, and I believe it definitely has a limit on the number of Floquet modes you can use in a Floquet port (see attached image). Is there a newer version of HFSS that does not have that restriction?

[kaleor]

Just an update on my end here I obtained the most recent version of HFSS (2021 R2). The limit on the Floquet modes still exists in this version. Again, is this because of memory requirements? HFSS's internal solution process? Or algorithm instability?
Thank you!

[Praneeth]

For the Floquet port, the mode calculator can only allow up to 100 modes.
But if you know the attenuation constants for the required modes then you can enter them manually.
Using this way, you can add more than 100 number of modes.
All the very best.

[kaleor]

Hi @pmunaga Thank you for the clarification!
I gave that a try, but I still came up with an error. I added more modes to the Floquet port by editing the .aedt file directly as shown in the image below. I calculated the attenuation constants that I would need for the additional modes.
I checked to make sure that the new modes registered in the project after I edit the file. They did, and this is shown in the screenshot below.
The error that still came up occurred after I ran the validation check. It complained that I cannot have more than 100 modes specified in the Floquet port.
Because of that, it seems like there is a hard limit on the number of Floquet modes. Does this limit exist because of limitations of the algorithm used to solve problems with a Floquet port? Or is it an arbitrary limit?
Thank you!