## Electronics

Topics relate to HFSS, Maxwell, SIwave, Icepak, Electronics Enterprise and more

#### What variable to input into HFSS to simulate an absorber ?

• Vu Vuong
Subscriber

I have chart above detailing the characteristics of the material which include: real permitivity , imaginary permitivity , real permeability, imaginary permeability.
Then I gathered the data and put into excel file, from there, I work out the absolute value of permitivity/permeability from the complex number

For example: let say my real permittivity is 4 Imaginary permittivity is 1 => absolute permittivity will be √ (42+12) = 4.12

Then I input this absolute value into HFSS.

Now here is the issue.

Some people said I should input the real permitivity instead and I don't need to work out the absolute value like above?

Some people said I should dividing the real permitivity by the vaccum permitivity instead then input the relative permitivity?

Some say the data in my chart is already relative value?

It is totally confusing to me, so can someone please help explain to me?

• GioF
Ansys Employee

Hi Vu Vuong,

I am not sure where your graphs are derived from but in general the permittivity of dielectrics is given by the equation,
ε = ε' - jε''

The relative permittivity is defined from the real portion of ε from the equation,
ε'=εr * ε0

You can find more information on relative permittivity under the HFSS Help, in the following link:
Ansys HFSS - Relative Permittivity

I hope that helps.

• Praneeth
Ansys Employee

Hi Vu Vuong,

Please note that you can enter these measured values as relative permittivity and dielectric loss tangent properties for a custom material in HFSS. Please go through the "Materials Technical Notes" section of the HFSS Help document for detailed information on how to correlate the measured values in terms of relative permittivity and dielectric loss tangent properties.

As you have frequency dependency then you need to add these properties as data sets. Detailed information on how to enter frequency dependent data sets can be found in "Assigning Frequency Dependent Material: Enter Frequency Dependent Data Points" section of the HFSS Help document.

Best regards,
Praneeth.