Absorber Material Modeling in HFSS

[emadi]

hfss absorber

Hi everybody
I am designing an antenna and I need to simulate the effect of an absorber material on top of my antenna....but I don't know how to model it.
thanks

 

[Tucco]

eccosorb+hfss

Hi,
If you don't know material properties of your absorber (and at the frequency you work), it's very difficult to have a good idea of the impact on your circuit or cavities.
There are a lot of absorbers, with very different properties.
In a general way, at RF frequencies:
Er value between 8 to 30 with dielectric loss tangent between 0 to 0.5
Mur value close to unity with magnetic loss tangent between 0.5 to 1.5

All absorbers I know are material in which magnetic losses are dominant.
It's fo EMI Shielding, Isolation, Resonant Cavity suppression.... ?
Each applications have its material. See datasheet of suppliers.

 

[geminiying]

hfss absorber modeling

I also facing the same problem as emadi..
I designing a parallel-plate waveguide dielectric probe, working with the freq range of 1 to 10 GHz; I dunno hw to model the absorber
I'm using Emerson & Cuming Eccosorb AN series(the attached file is the datasheet)
but it doesn't tell me much about the properties of the absorber..
Can somebody help me too?

 

[Tucco]

absorbant hfss

Hi,
You can try to approximate the material properties with solving the inverse problem: that is in making EM 3D simulations for search a return losses profile fitting the Eccosorb's datasheet curves.

But before, to avoid to run a thousand simulations, it's important to understand that absorber , in a specific thickness (1 cm for AN73), have a max absorption (so a minimal return losses) close to its effective quarter wavelength.
So you can determine the propagation constant (and the product er.mur)
which respect this condition. Their are 2 solutions but the level of RL depends of the ratio mur/er (impedance of the material ). Thus, it's possible to approximate values of er' and µr' for initalize 3D simulations and make some trial around it with different values of losses (you can try with er''=0 and make variation of mur" )

This method have limits because you have no information about phase S11, and because parameters could be frequency dependent. --> long work !
But I think it's the only method to have indicative values when you have no more information.

 

[prafuldeo]

modeling absorber material

If you use CST they have preloaded Eccosorb materials. u can use it directly. Else you can use the data sheet of the materials..