simulation in HFSS

[SamiraAmiri]

hello
I want to simulate an underwater antenna in HFSS. does anyone know anything about it?
I want to put antenna in a box and then submerge the box in to water. Does anyone know how I can determine radiation box? my radiation box is water? or I should use PML for defining water as the medium?

 

[aliarifat794]

If your simulation setup needs an open boundary, then you may need to add a radiation boundary outside the water box.

 

[volker@muehlhaus]

I wonder if the HFSS radiation boundary works for other media other than air. In the EM tools that I use, absorbing boundary is designed to give E/H = 377 Ohm

 

[vfone]

In HFSS right click on Boundaries/Edit Global Material Environment, click on default material (which is vacuum) an choose the material you want.
There are few options for water: water 0.2-35C 0.1-400GHz, water_distilled, water_fresh, water_sea.

 

[SamiraAmiri]

Many thanks to all of you ...

another question?

Should I use a box with the material of water for the radiation box?

Should this box be as far away from the structure as lambda/4?

 

[vfone]

If the antenna is submerged in water, yes you can use the radiation box filled with water.
Generally the safest distance from an antenna to don't get any interference is 2λ. But this distance depends by the type of antenna, where dipoles are more affected and monopoles less affected. However, for some cases the distance could be reduced to λ/4, but not less.

 

[SamiraAmiri]

If the antenna is submerged in water, yes you can use the radiation box filled with water.
Generally the safest distance from an antenna to don't get any interference is 2λ. But this distance depends by the type of antenna, where dipoles are more affected and monopoles less affected. However, for some cases the distance could be reduced to λ/4, but not less.

thanks so much
I have another question.

which way should I follow for modeling of the structure?
1) antenna structure + box of water + box of radiation (water material) (at least lambda/4 distance)
2) antenna structure + box of radiation (water material) (at least lambda/4 distance)

 

[vfone]

If you want to simulate the antenna operating in a realistic environment with a surrounding box of water, you can set up the following structure:
1. Antenna structure placed inside a box of water (dielectric material defined as water).
2. Radiation box surrounding the antenna and the box of water.
This setup allows you to analyze the interaction between the antenna, the water box, and the radiation box, providing a more accurate representation of the antenna performance in a water environment.

If you are only interested in analyzing the antenna's radiation characteristics when exposed to a water environment, you can set for comparison:
1. Antenna structure without a box of water.
2. Radiation box surrounding the antenna with the dielectric material defined as water.
This configuration shows how the antenna radiates in the presence of water, without considering the effects of the water box itself.

 

[SamiraAmiri]

If you want to simulate the antenna operating in a realistic environment with a surrounding box of water, you can set up the following structure:
1. Antenna structure placed inside a box of water (dielectric material defined as water).
2. Radiation box surrounding the antenna and the box of water.
This setup allows you to analyze the interaction between the antenna, the water box, and the radiation box, providing a more accurate representation of the antenna performance in a water environment.

If you are only interested in analyzing the antenna's radiation characteristics when exposed to a water environment, you can set for comparison:
1. Antenna structure without a box of water.
2. Radiation box surrounding the antenna with the dielectric material defined as water.
This configuration shows how the antenna radiates in the presence of water, without considering the effects of the water box itself.

Thanks a lot. I got my answer.

I want to build the antenna in reality. This antenna place in a PVC box and then submerge in seawater in the depth of at least 10 meters working with Wi-Fi. Do you know how I can consider 10 meters of water in HFSS?

 

[vfone]

I don't think you will get any signal at 2.4GHz after 10m of water.
According to the research attached, there is huge attenuation for much smaller water thickness:

https://www.researchgate.net/figure/Radio-wave-attenuation-by-sea-water-as-a-function-of-thickness_fig3_340683649

In terms of how antenna is influenced by the water (impedance, gain, efficiency, etc.) I think that 10cm or 10m of water will do pretty much the same influence.

 

[SamiraAmiri]

I don't think you will get any signal at 2.4GHz after 10m of water.
According to the research attached, there is huge attenuation for much smaller water thickness:

https://www.researchgate.net/figure/Radio-wave-attenuation-by-sea-water-as-a-function-of-thickness_fig3_340683649

In terms of how antenna is influenced by the water (impedance, gain, efficiency, etc.) I think that 10cm or 10m of water will do pretty much the same influence.

it helps me a lot.
How about 433MHz? Can I use this frequency?

 

[vfone]

At 433MHz attenuation in salt water is smaller compared to 2.4GHz.

https://www.researchgate.net/figure/Attenuation-experienced-by-EM-signals-in-fresh-and-seawater-for-different-frequencies_fig1_302259776

 

[SamiraAmiri]

Thanks a lot

At 433MHz attenuation in salt water is smaller compared to 2.4GHz.

https://www.researchgate.net/figure/Attenuation-experienced-by-EM-signals-in-fresh-and-seawater-for-different-frequencies_fig1_302259776

 

[volker@muehlhaus]

At 433MHz attenuation in salt water is smaller compared to 2.4GHz.

That is true, but both values are extreme.

Above I read "submerged in the depth of at least 10 meters working with Wi-Fi" and this means attenuation to the surface will be much too large at 433 MHz also.

 

[FvM]

There are some literature results for lower frequencies up to 20 MHz https://www.researchgate.net/public...propagation_at_MHz_frequency_through_seawater

Best results are apparently achieved with dipole antenna submerged in a box with deionized water

This overview article has also references to 2.4 GHz underwater propagation https://pmc.ncbi.nlm.nih.gov/articles/PMC4934316/

 

[SamiraAmiri]

That is true, but both values are extreme.

Above I read "submerged in the depth of at least 10 meters working with Wi-Fi" and this means attenuation to the surface will be much too large at 433 MHz also.

Yes, That's right.

--- Updated Nov 17, 2024 ---

There are some literature results for lower frequencies up to 20 MHz https://www.researchgate.net/public...propagation_at_MHz_frequency_through_seawater

Best results are apparently achieved with dipole antenna submerged in a box with deionized water

This overview article has also references to 2.4 GHz underwater propagation https://pmc.ncbi.nlm.nih.gov/articles/PMC4934316/

Thank You.
Jaime Lloret Mauri is my supervisor. I have said to him that in 2.4GHz, attenuation is so high. He told me that " I know, but I want to do it".
So, I have to try different lots of solutions to get answer.
Anyway, if anyone can help me with the simulation, I will appreciate it a lot.