Non Destructive Technique to Characterize the Permeability of Material in the Microwave Range: Evaluation and Analysis of the Measurement Uncertainties

We present in this paper the results of the characterization of a magneto-dielectric layer, as well as the associated uncertainties. A non-destructive and non-contact technique has been developed to determine the microwave characteristics of a layer of magneto-dielectric material covering an object. The method is based on a reflection measurement and assumes that one of the radioelectric characteristics is known. The measured signal, reflected at the surface of an object under test, is compared to a numerical calculation taking as input variable the desired microwave characteristic, and then this one is determined by solving an inverse problem using the calculated and measured points. To obtain the desired characteristic with a good accuracy and perform Non-Destructive Control, the uncertainties of the numerical calculation and the measurement must be low. The first step is the evaluation of the uncertainties, then their calculation, and finally their analysis, possibly with their reduction. This article presents the characterization of the magnetic permeability of a magneto-dielectric sample, associated with the main interest of this work: the evaluation of the uncertainties for this measurement method.