Surface Impedance Estimation of a Stretchable Material

Stretchable materials are widely used for the realization of various sensors but their radio-frequency behavior is still little explored today. Here an innovative method is proposed that allows to derive the surface impedance of such materials. This parameter is fundamental for obtaining a calibration curve of these materials for their employment as a sensitive element. The proposed method allows to obtain the surface impedance of the material while it is being stretched and is based on a contact-less measurement of the scattering parameters. By exploiting these parameters and thanks to an inversion procedure, it is possible to obtain the value of the surface impedance as the frequency and strain vary.