This paper presents an accurate free space method for material characterization eliminating the problem of the required precise orientation between the material and the antennas and expanding the unambiguous range for electrical thick samples. It includes theoretical considerations and measurement results of four different materials. Overall, a maximum measurement uncertainty of 0.0153 for the relative permittivity and 0.001 for the loss tangent in the W-band can be achieved. Depending on the variation of the material's thickness, the implemented setup changes lead to an reduction of the measurement uncertainty of 8 to 58 %.
