Improvement of the permittivity measurement by a 3D Full-Wave analysis of a Finite Flange Coaxial Probe

Open-ended coaxial probes are commonly employed for the dielectric characterization of materials due to several well-known advantages. This measurement technique, consisting in measuring a reflection coefficient, Gamma involves an inversion procedure: given the measured Gamma the unknown complex permittivity, epsilon(M) of the material under test (MUT) is computed by means of an electromagnetic (EM) model of the probe contacting the MUT. For this purpose, a mixed analytical/empirical/full-wave optimization to permittivity measurement is here proposed. The experimental results obtained by a 3D full-wave model of the finite-flanged coaxial probe in the 2-3 GHz range, are discussed by comparing with those computed according to an analytical EM model involving an infinite flange [1]. The effect of the flange size on the permittivity measurement precision is also analyzed.