Reconstruction of The Structure of the Electrophysical Parameters of Multilayer Dielectric Materials and Coatings from The Frequency Dependence of the Attenuation Coefficient of the Field of a Surface Electromagnetic Wave

A new radio-wave method of reconstruction of the relative permittivities and thicknesses of multilayer materials and coatings is proposed. The method is based on the solution of inverse problems in the reconstructionof the structure of the electrophysical parameters of special multilayer materials and coatings from the frequency dependence of the attenuation coefficient of the field of a slow surface electromagnetic wave. The principal differences of the new method from well-known radio wave methods of determining the electrophysical parameters of multilayer materials are demonstrated. In contrast to methods that involve an informative parameter – the complex reflection coefficient – the proposed method yields an increase in the precision and reliability of the reconstruction of the structure of the relative permittivitties and thicknesses. Improved precision and reliability is achieved by taking into account the linear dependence of the attenuation coefficient on frequency as well as reducing the number of fixed measurement frequencies. The results of experimental studies that confirm the linear dependence of the attenuation coefficient of the field of a surface electromagnetic wave on frequency as well as a decrease in the number of fixed measurement frequencies are presented. The method implements a simple measurement procedure, since only the values of the field strength of the surface electromagnetic wave are measured and there is no need for phase measurements in the method. Reconstruction of the permittivity of a three-layer coating consisting of polymethyl methacrylate, F-4D PTFE, and semi-hard rubber with precision acceptable for practical applications is realized with the use of experimental results of measurements in a multifrequency measurement complex in the range 9–10 GHz by means of the new method. Experimental investigations of a multilayer dielectric coating demonstrated the theoretical capabilities gained with measurement of the relative permittivity and thickness of the individual layers with relative error not greater than 8 and 6%, respectively.