Improving the accuracy of measurements of the bistatic scattering characteristics of material samples of various configurations

We study the bistatic scattering properties of the samples of radio-absorbing composite materials and analyze the impact of diffraction effects at the edges of flat samples of small sizes (2–4 wavelengths of the incident wave) on the results of measurements of the reflection coefficient for a sample material, i.e., a bistatic characteristic that depends on the frequency of radiation in a broad range of the angles of incidence (10–85°). To reduce the influence of diffraction effects, we designed samples of various configurations made of magnetodielectric materials with frequency dispersions of dielectric and magnetic permeability. The samples have the form of metal plates one side of which is covered with the investigated material, while the other surfaces of the plate are covered with radiation-absorbent material. The scattering characteristics of the developed samples are numerically evaluated and experimentally measured on a bistatic installation in the anechoic chamber. The experimental data correspond to the numerical results. We observe a noticeable weakening of the influence of diffraction effects on the values of reflectivity in broad angular and frequency ranges. By using the numerical methods from the FEKO software package, we studied the influence of the configuration of samples on the systematic error of measuring of the reflection coefficients.

It is also shown that this error can be reduced by using substrates of elongated shape in the plane of incidence (samples of hybrid configurations). The accumulated results can be used to measure the scattering characteristics of the materials in the free space, e.g., in refining the characteristics of the material.