Dielectric properties characterization: A simple inverse problem approach

A non-resonating technique for characterizing isotropic complex permittivity of dielectric substrates is presented. The technique is applicable to high or low ε
_r
and tan δ values. After measuring the S
₂₁
of a microstrip line with the unknown substrate, an inverse problem is built with an EM solver. Then, the complex permittivity parameters are extracted by means of solving the inverse problem using the Differential Evolution algorithm. The validity of the technique is assessed by characterizing two known and reliable dielectrics, in which the maximum error for the ε
_r
and tan δ was 7.6% and 16.67%, respectively.