Контроль диэлектрической проницаемости и толщины анизотропных диэлектрических покрытий методом поверхностных электромагнитных волн

The widespread use of anisotropic composite dielectric coatings operating in the microwave range in various science-intensive areas has led to the search and selection of effective methods of radio wave nondestructive testing of their electrophysical parameters. The existing approaches based on the estimation of the reflection and transmission coefficients of electromagnetic waves have low accuracy and reliability of estimating the components of the complex permittivity tensor and the thickness of such coatings, do not take into account their frequency dispersion and placement on a metal base. We present the new method of local measurements of components of the complex permittivity tensor with allowance for their frequency dispersion and a thickness anisotropic dielectric coatings with radial surface microwaves. The method is based on the solution of inverse problem in the determination of components of the complex permittivity tensor and a thickness coatings from the frequency and angular dependence of the attenuation coefficient of the field of a radial surface electromagnetic wave excited in a test sample. A numerical and experimental study show that for a measurement bandwidth of 9–13,5 GHz the errors in estimating the anisotropy coefficients do not exceed 10% with a confidence coefficient of 0.95. We introduce and substantiate a statistical limit of the resolution of the anisotropy of permittivity; this makes it possible to evaluate the possibility of discriminating between two close values any pair of components of the permittivity tensor. Numerical and field experiments have shown that the method can provide their assessment with a difference of 0.2–0.3% or less in the frequency band of 9–13.5 GHz.