DUAL COAXIAL PROBES IN TRANSMISSION INSERTED BY DIELECTRIC WITH TWO DIFFERENT THICKNESSES TO EXTRACT THE MATERIAL COMPLEX RELATIVE PERMITTIVITY: DISCONTINUITY IMPACTS

After a thorough investigation, this paper introduces a novel and simple radiofrequency material characterization technique. For this study's purposes, two probes were developed and separated by the sample under test (SUT) with an inhomogeneous test cell. Furthermore, the discontinuity impacts at the probe, SUT interfaces, were also studied. The investigation uses the transmission process through the principle of two different SUT thicknesses to measure its relative permittivity and loss tangent. The technique is based on using the lumped elements of an equivalent circuit of the entire test cell and covers 1 MHz-2 GHz. With the SUT, placed between two metal probes and another metallization, placed under its thickness on an opposite side to improve the loss tangent acquisition level, the cascading chain matrix (CCM) is used to get the final parameters. The thickness changing makes it possible to overcome the contact interface effects probe-sample. A mathematical model has also been presented through the fitting procedure. The new technique has been validated with three materials: Rogers RO4003C, FR-4 HTG-175, and Alumina 99.6%. The SUT complex relative permittivity extraction makes the new approach suitable for the telecommunication industry and many others. The method is also ideal for materials with thickness sizing up to 3 mm around.