Impact of radiation box shape on antenna gain in HFSS

[MuroSamuro]

Hello,

I modeled a basic horizontal lambda0/2 dipole above a ground plane.

Initially, I simulated the dipole in free space, yielding a reasonable antenna gain of 1.64 (or ~2.14 dBi).

Next, I simulated it over an infinite ground plane. While the normalized radiation pattern stayed consistent, the gain fluctuated with changes in the radiation box shape (rectangular, cylindrical, and spherical).

For example, with a rectangular radiation box, the gain raised to 6.88, over four times the gain of a single horizontal dipole (that is the correct number, i.e. 6.56).

Has anyone encountered a similar issue?

Thanks.

 

[PlanarMetamaterials]

If the ground plane intersects the radiation box, I'd not be surprised by such behavior. You're taking a farfield transformation of some propagating surface waves, which probably invalidates some assumptions made about the modes incident on the radiation boundary, resulting in a highly curvature-dependent result.

I might suggest replacing the radiation boundary with a PML, to see if you get similar results to the rectangular case. Also, I might suggest simulating a finite, but large, ground plane to see if the results are similar to any of the other cases.