When simulating an antenna in a water medium in HFSS, the radiation boundary box should ideally represent the surrounding medium accurately. Here's what to consider:

By setting the radiation box material to water and carefully assigning boundaries and materials, you can achieve accurate results for your antenna's performance in the submerged scenario. Let me know if you need detailed steps for setup!

thanks so much for the complete answer.

I have question about boundary condition. How can I consider it in HFSS?

Defining the Water Medium: Define the water material in HFSS with the following properties:Relative Permittivity (εr): approximately 78 (at 20°C). Conductivity (σ): around 0.001 S/m (for fresh water). Magnetic Permeability (μ): approximately equal to free space permeability (μ = μ0).

With these settings, you can simulate the antenna's behavior in the water medium in HFSS.

Now I'm confused: which material I should use for the radiation box?

The first answer says water.

The second answer says air or vacuum.

Anyway, which one is correct? The results are so different.

The choice of material for a radiation box depends on the scenario you are trying to recreate. For an antenna submerged in water, you would use water as the radiation box medium. However, for an antenna that is placed into water and then removed, you would use vacuum or air as the radiation box medium. The medium of the radiation box should mimic the environment in which the antenna operates. I hope this helps.