## 6 Conclusions  
The method for measuring the electrophysical parameters of materials based on measurements of the transmitted and reflected signals obtained under the condition of ensuring the incidence of a plane wave on the material under study was developed. Numerical and analytical calculations were carried out, and the design of a laboratory model was calculated and developed, with which a number of confirming experiments were carried out. The use of a reflector made it possible not only to achieve a collimated beam on the surface of the measuring laboratory model, but also improve the measurement accuracy. In addition, the proposed design allowed measurements outside the anechoic chamber, was devoid of complex mechanics, and was also not demanding on lateral and/or external radiation, did not require precision expensive equipment, absorbers, and was free from other disadvantages. Mathematical processing excluded extraneous radiation by extracting a useful signal using a time window.  
To obtain the most accurate values of electrophysical parameters, the size of the measured sample should not be less than 150 \(\times\) 150 mm. This is due to the size of the focusing area on the surface of the laboratory model. The thickness of the material must be at least 5 mm. The obtained experimental data showed a high measurement accuracy of simple materials with known values of dielectric permittivity. The level of error for materials such as plexiglass and textolite was 0.3% and 1.1%, respectively.  
This research is of great scientific and practical importance.  
The scientific significance of this work lies in the fact that there is no focusing lens (we used a parabolic reflector made of metal) made of a dielectric material, which means that there is no frequency dispersion and the data obtained is more accurate when compared to a kit for dielectric measurements, for example, from Keysight Technologies. A single-port measurement was also used, thus there is no need to use a vector analyzer and it is possible to use a vector reflectometer.  
In addition, the existing SPEAG installations are contact methods, however in our case the non-contact method and addition of polystyrene is necessary for the convenient placement of the sample. There is no need to prepare material for research. In a large-scale industry, the production of materials requires an examination of the batch. For a line of existing installations, special preparation of the size is required, as well as thickness control, which is not always convenient. Another not unimportant factor of the developed method is the possibility of measuring not ideally smooth samples.  
Conceptualization, S.S., V.Y.; methodology, A.G., K.Z., S.S.; validation, A.G., A.M.; formal analysis, A.M., S.S.; investigation, V.Y.; resources, A.G.; data curation, A.G., A.M., V.Y.; writing--original draft preparation, A.G., K.Z., A.M., S.S., V.Y.; writing--review and editing, A.G., K.Z., A.M.; visualization, A.M., A.G.; supervision, K.Z.; project administration, S.S. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Ministry of Science and Higher Education of the Russian Federation, project N\({}^{\circ}\) 0721-2020-0038.  
**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.