Edge effects in bistatic measurements of scattering characteristics of material samples.

Abstract

This work is devoted to studying errors emerging by the edge effects when measuring the reflection coefficient (R) and when finding Brewster angle. The impact of edge effects on the scattering characteristics of planar material samples with different geometries was considered. The method of moments in the FEKO program and analytical calculations using Fresnel formulas are used to study a model material with frequency-independent parameters of the medium. A plane linearly polarized wave falling on the object was studied. For each incidence angle of the wave, the electromagnetic field reflected from the object in the mirror direction was calculated. To calibrate the received signal a reference metal plate of the same size as the size of sample under study was used. To estimate the contribution of the finite-size of the sample in the of reflection coefficient, the simulation results were compared with analytical calculations using Fresnel formulas. The results of the electrodynamic simulation of the characteristics of the model material showed that the position of the sample relative to the polarization of the incident wave does not affect the R value; an increase in Brewster angle depending on the frequency was observed. The reflection coefficient of a square sample with a radar absorbent material (RAM) on a metal substrate was investigated. Measurements of the sample scattering characteristics were carried out in an indoor electromagnetic test bistatic facility (anechoic chamber) in ITAE RAS. The experimental results are in accordance with the calculated data obtained by the method of moments and analytical data. For the sample under study, the value of Brewster angle was not determined due to the fact that this value is outside the measurement range. A significant influence of edge effects on the reflection coefficient of the material sample was revealed, especially for angles closed to Brewster angle.