Learning Forum

[Miguel Gonzalez]

Hello All

I am trying to simulate a coil in HFSS but I do not know how to size the radiation boundary. I have read that it should be at least 1/4 of the wavelength. I am simulating it at 13.56MHz, which have a wavelength of  22m, so 22/4 is equal to 5.5 , right now I am sizing my radiation boundary (sphere) with a radius of 6m. If I increase the boundary size then the quality factor starts to change. I don't know if I am simulating it properly.

I would like to hear any feedback.

Thanks,

Miguel

[Connor Pope]

You can automatically make your radiation box by right-clicking your geometry and selecting "Create Open Region...". Put in the frequency you want and it will auto-create the air-region and boundary around your structure. It may or may not be a similar size to what you've already selected. 

The size of your coil structure looks in the ~10-100 mm radius range. The size of your air box is many times greater than this, ~5000mm radius range, so 50x - 500x times bigger. Perhaps the meshing is not as tight as it should be near the coil geometry itself because of how big the air box is relative to it. You can try seeding your coil geometry with a specific lambda/N value so it has a smaller mesh. Maybe that will give you a more stable quality factor?

Seeding means you "Assign Mesh Operation" and select either "On Selection" --> "Length Based..." for surfaces, or "Inside Selection" --> "Length Based..." for volumes. The value you select is some fraction of the wavelength you're looking to simulate. The lower values you select for seeding the more RAM you'll need, more time the simulation will take.

HFSS is a lot better for higher frequencies than lower frequencies, but maybe there are better ways to use it for these lower frequency ranges.

[Anchal Singh]

Hello Miguel,

You can create an open region for this case. It will automatically make the radiation box for your design. You can do so by right mouse clicking on the design name in the project manager and choosing 'Auto Open Region' under the solution type dialogue box.

To learn more about boundaries in HFSS, you can go through the HFSS Help document - Assigning Radiation Boundaries

Hope this helps!

 

Regards

Anchal

[Mrinmoy Bharadwaj]

You can also update your region size depending on the solution frequency.