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.