Testing of electrophysical parameters of multilayer dielectric and magnetodielectric coatings: evaluation of the resolution of the method of surface electromagnetic waves

The problem of reconstruction of the distribution of dielectric permittivities and magnetic permeabilities over the thickness (profile) of nonmetallic coatings is of high priority in connection with an increasing role of contemporary methods of radio-wave nondestructive testing aimed at the evaluation of the quality of materials and products of various kinds. The radio-wave methods were successfully used to reconstruct the distributions of dielectric permittivity and magnetic permeability over the layers of multilayer dielectric and magnetodielectric coatings on metal substrates. The resolution of the method of surface electromagnetic waves was studied in terms of the dielectric permittivity and magnetic permeability, namely, the difference between the values of these quantities was analyzed for the adjacent layers of multilayer dielectric and magnetodielectric coatings, respectively. We develop an original procedure for estimating the limiting resolution of the method of surface electromagnetic waves depending on the electrophysical parameters of the layers of a coating, the number of measurement frequencies, the bandwidth of measurement frequencies, and the standard deviation of noise affecting the results of measurements of the attenuation coefficients of the field of surface waves. We describe the structure of a measuring complex implementing the developed procedure. The results of numerical and full-scale experiments aimed at the estimation of the resolution limits for the dielectric permittivity and magnetic permeability of the layers of two-layer coatings of various types are presented. The numerical experiments were performed on a sample of two-layer radar-absorbing coating, while the full-scale experiments were carried out on a sample of two-layer dielectric coating based on the Ro4003C and Arlon25N materials. It was established that the results of numerical and full-scale experiments coincide, which confirms that the proposed procedure is adequate. For a bandwidth of measurement frequencies 9.0–12.5 GHz and a standard deviation of noise equal to 0.002, the resolution limit in terms of the dielectric permittivity and magnetic permeability of layers is guaranteed within the range 0.25–0.50% The proposed procedure can be used in various fields of science to estimate the electrophysical parameters of multilayer coatings in the course of efficiency tests.