A significant investigation on the use of two probes in the transmission is presented in this paper. As a transmission-line technique, those two probes separated with a variable thickness of the sample under test to determine the material dielectric constant from the transmission phase constant constitute the basis of the proposed technique novelty. This new approach replaces each configuration's measured electric length to widen the covered frequency range through the new phase definition or model. Using the material thickness and the probe inner conductor dimension through a mathematic function model to get to the material's complex relative permittivity (dielectric constant and loss tangent) is the best way to include discontinuity impacts in this concept to reach the goal. The approach has been tested on the standard materials: FR4, Alumina 99.6%, and Roger RO4003C with thicknesses between 0.79 mm and 2.0 mm. In addition, the Anritsu MS4642B 20 GHz Vector Network Analyzer (VNA) has been used to scan the frequency range 1.7–3 GHz and validates the approach. Metal in contact with both probes is placed under the controlled space representing the material thickness to improve the loss tangent extraction. One test cell is fixed, while the second is movable.