A dielectric loaded resonator for the measurement of the complex permittivity of dielectric substrates

A new configuration of dielectric loaded resonator, particularly versatile for the complex permittivity measurement of substrates for microwave circuits, even in presence of back metal plates, is here shown. In order to test this technique in a wide interval of the values of the complex permittivity, the versatility of 3D-printing is exploited to print samples with different densities, thus artificially changing the effective permittivity in the interval (1.7–3.1) for the real part and (0.02–0.06) for the imaginary part. The designed resonator, tuned at ~ 12 GHz is experimentally validated by the comparison of measurements obtained on these samples with a split ring resonator and standard transmission/reflection waveguide methods. Then, the versatility of the designed resonator is shown on the characterization of FR4-fiberglass and Kapton® polyimide samples.