A New Calibration-Independent Method for Complex Permittivity Extraction of Solid Dielectric Materials

Microwave nonresonant methods generally require some sort of calibration before conducting the measurements. Calibration-independent nonresonant methods are very attractive since they eliminate this need. In the literature, different calibration-independent methods for complex permittivity determination of materials have been proposed. While some of them use uncalibrated S-parameter measurements of two identical samples with different lengths, the others utilize the same measurements of one sample. The advantage of the latter methods is that they eliminate any impurity and/or inhomogeneity present in the second sample and avoid any thickness uncertainty that can arise from using the second sample. In the literature, the proposed approaches in latter methods, however, require precise location of the sample inside its cell (a waveguide or coaxial-line section) or exact shifting distance of the sample inside its cell. This letter proposes a method to eliminate these requirements using uncalibrated S-parameter measurements of an extra cell (empty) and the cell, in which the sample is arbitrarily located.