Determination of constitutive parameters of homogeneous metamaterial slabs by a novel calibration-independent method

A calibration-independent line-line method for broadband and simultaneous constitutive parameters determination of homogeneous metamaterial (MM) slabs is proposed. It is shown that the sufficient condition for parameters retrieval by the proposed method is to measure uncalibrated (raw) complex scattering parameters of measurement cells (different air regions in free-space) which are completely and partially loaded by the two identical metamaterial slabs. The stability of derived equations for different measurement uncertainty cases is analyzed. We have validated the proposed method by using simulated scattering parameters of a MM slab with split-ring-resonators and then by comparing the extracted electromagnetic parameters with those of a general method used in the literature in the cases with and without a small offset in reference-plane positions (as well as other measurement errors). From this comparison, we note that while the general method does not eliminate those errors, the proposed method not only does not introduce the non-physical anti-resonance behavior but also removes the measurement errors arising from different mechanisms such as inaccurate reference-plane positions and mismatched connections.