Permeability Measurement of Metamaterials with Split-Ring-Resonators Using Free-Space Calibration-Independent Methods

A calibration-independent microwave method is proposed for complex permeability extraction of metamaterial structures composed of periodic split-ring resonators. For the retrieval process, uncalibrated (raw) complex scattering parameter measurements of three measurement configurations in free-space are utilized. Two metric functions are derived for retrieval of complex permeability of homogeneous metamaterial slabs even when their lengths are unknown. The method is validated by retrieving the magnetic properties of some homogeneous SRR metamaterial slabs with a pre-assigned magnetic resonant frequency.