Re: microwave absorber modeling in HFSS

the pictuer that i attached had an exaggeration for distinguishing. the real distance that i used is 2 mm from PML for front of antenna in 10GHz.

you mean that the distance should be zero and the pml should attach to the structure.?!
can you attach an instance please?

Hi J.C.Maxwell,

What exactly are you trying to do with that setup? The radiation boundary needs to be at least a quarter wavelength from the radiating portions of the antenna in order to computer the radiation patterns properly. When I say the absorber needs to be attached to the antenna, I mean to absorb backwards directed fields. I assume the radiating aperture in this case is facing the positive z direction.

i think i misunderstand your word.
in these attached pictures i used a horn antenna for test the PML operation.
i want to use a PML in front of this horn to see how much it could damp the signal. you said that use PML should be lambda/20 away from the radiator. and i did what you said but no change happened.
so please help more .
i want to test PML. i want to damp the signal in front of this horn antenna in 10GHz. i have 27dB for electric field in front of horn, and i want to reduce it to 5dB with PML.

This has nothing to do with your original post. No wonder you are confusing everyone.

A PML works a perfect absorber. What you want is an attenuator. If you want to do this from a material perspective, you need to calculate the medium parameters. And, of course, the material needs to be inside the simulation domain, not on the edge or outside of it.

A much better solution would be to insert a waveguide inline attenuator.

hi all.
guys i am completely confused about this problem.
let me to explain in another way.
according to attached picture i want to cancel the coupling between balun and planar spiral(in hfss).
i want to place a material around balun to prevent coupling effect on radiating spiral. in experiment we'll use absorber to reach that goal. but now i want to do this in simulation. please help me solve this guys. thank you very much.

Hi J.C.Maxwell,

I'm not sure if an absorber will adequately cancel near-field coupling like that (but I could be wrong). You may have to investigate shielding and opposed to absorbing.

A PML *might* work in this case, I would put one inside your simulation domain with the absorbing face facing the antenna.

Good Luck

hi PlanarMetamaterials .
i tried the PML but it didn't work.

How did you set up the PML? A picture would be great. It's possible that your setup was correct - if this is the case I think this would be a good indication that a regular absorber won't work either for the reason mentioned in my previous post.