Electrodynamic Model of the Signal Scattered by the Multilayer Structure with the Use of Physical Optics and Ray Tracing Technique

Abstract

Introduction. Remote monitoring of layered underlying surfaces is an urgent task. To assess the performance of new algorithms for processing the radar signal reflected from the surfaces, full-scale tests are required. As their carrying out demands big expenses, simulation modeling is actual. There are many methods of estimating an electromagnetic field (EMF) scattered by the earth's surface. However, there are no proven methods and algorithms for engineering calculation of the reflected radio signal in the conditions of this problem.Aim. The aim is to develop and to verify a software model to simulate the reflected multilayer extended structure of the radio signal received on board the aircraft.Materials and methods. The core of the model was based on high-frequency electrodynamics' methods, which allowed rapid calculation for large areas of targets with any number of layers. Simulation was produced using the MATLAB software package. The developed simulation model represented the result in the form of the normalized radar cross-section (RCS) of the multilayer structure. Since the layered structure had rough boundaries, the model provided triangulation of the boundaries of the volume-distributed object. The resulting EMF was calculated using the superposition principle. Each partial EMF value on the facet was calculated taking into account the phase and the polarization of the locally incident EMF.Results. In the paper the comparison of simulation results with theoretical calculations for the normalized RCS of a two-layer structure (difference is less than 10 percent) was presented. Verification for the coefficient of variation of the envelope of the reflected radio signal from the depth of groundwater (critical error was 7 percent) was performed. RCS modeling of the absorbing layer with different degrees of roughness of the layer boundaries was carried out. The upper boundary roughness (for maximal height deviation 0.1 m) affected on specific EPR more than lower boundary. It manifested itself in decreasing of RCS down to 30 dB.Conclusion. The developed model is intended to reduce expenses for designing synthesis of subsurface imaging systems with comparison of scheme "model of device development – field tests – completion – etc". The model is designed to verify the new signal processing algorithms for subsurface radar.