Creating a circular cavity helix antenna

I’m working on designing a helical antenna placed inside a circular cavity. I have a few questions regarding the modeling:

When using the helix function, I must specify a ground plane. By default, it is a circular plate with a non-zero radius, and MATLAB throws an error if I try to set it to zero.

I want the circular cavity to act as the ground plane, so I don’t need the small helix disc.

If I include both the helix ground plane and the cavity in the simulation, will there be overlapping meshes, and does that cause problems for the solver?

Has anyone here designed or simulated a helical antenna inside a cavity in MATLAB? How did you handle the ground plane in your simulation?

Thanks in advance for any advice or experience!

Answer 1

[Broy]

Hi Jan,

I understand the challenge you are facing. You want the circular cavity to act as the primary ground for your helical antenna, but the helix object in MATLAB forces you to define a specific ground plane radius. This creates a valid concern regarding whether the built-in ground plane of the helix will overlap with the cavity base and potentially cause mesh intersection errors or solver convergence issues during the simulation.

To resolve this, you do not need to delete the helix ground plane entirely. The recommended approach is to:

• Set the helix's GroundPlaneRadius to be just slightly larger than the coil's Radius.
• Ensure the cavity Spacing property is kept very small.

Regarding your specific doubt about simulation errors: Overlapping meshes will not cause problems. The Antenna Toolbox solver automatically handles the contact between the helix’s small base and the cavity’s large floor by performing a Boolean Union, merging them into a single continuous electrical conductor.

Helpful Documentation:

• Helix Antenna: https://www.mathworks.com/help/releases/R2025b/antenna/ref/helix.html
• Circular Cavity: https://www.mathworks.com/help/releases/R2025b/antenna/ref/cavitycircular.html

Hope this helps.