Study On Electromagnetic Scattering From Layered Ground And Target

Most modern military wars take place in complex ground and sea environments,and the influence of the background of the target on radar detection and identification cannot be ignored.Usually,the background of the target is regarded as the rough surface of a single-layer medium,and only the electromagnetic scattering of the rough surface and the target above is studied.However,the composition of the actual natural environment is complex,such as vegetation-covered soil,snow-covered soil,oil spilled sea surface,floating ice sea surface,etc.,which are usually multi-layered media.During the study,in addition to the scattering of the rough surface and the free space above,attention should also be paid to the electromagnetic wave transmission between the upper and lower rough surfaces.Research on composite electromagnetic scattering of layered rough surface and target is beneficial to detect and identify buried objects in the ground,provide more accurate information for complex ground-sea military operations,and obtain information on soil moisture and plant maturity in the civilian field,etc.It has more important research value.This paper mainly studies the composite electromagnetic scattering characteristics of layered snow,soil rough surface and target,and focuses on the influence of various parameters on electromagnetic scattering.The main work is as follows:First,one-dimensional and two-dimensional random rough surface geometric modeling methods are introduced.The basic theory of random rough surface is expounded,and its commonly used statistical parameters are introduced.The geometric model of one-dimensional and two-dimensional random rough surface is generated by using Monte Carlo method combined with Gaussian spectral function.By discussing the correlation length and root mean square height change to study the effect of these two parameters on roughness.Secondly,the Method of Moments for electromagnetic scattering from one-dimensional single-layer rough surfaces is analyzed.The basic principles of the Method of Moments and the selection principles of basis functions and test functions are introduced.The Method of Moments equation for one-dimensional rough surface electromagnetic scattering is deduced in detail,and the formula for the cone wave and the equation for solving the scattering coefficient are given.The focus is on the effects of root mean square height,correlation length,incident frequency,and polarization mode on electromagnetic scattering from one-dimensional rough surfaces.Then,the two-dimensional single-layer rough surface and its composite electromagnetic scattering properties with the target are studied.The Multilayer Fast Multipole Method is introduced,and its processing steps for far-field coupling are described in detail.Two-dimensional rough surface and tank models are established by Rhino modeling software,and the influence of rough surface characteristic parameters,electromagnetic parameters and target geometric parameters on electromagnetic scattering is discussed,and the difference between the overall composite electromagnetic scattering and the single rough surface electromagnetic scattering is analyzed in combination with the target.Finally,the layered rough surface in the actual natural environment and its composite electromagnetic scattering properties with the target are studied.The equivalent dielectric constant models of common land backgrounds such as soil,snow,vegetation,sand,and concrete are discussed,and the effects of incident frequency and water content on the dielectric constant are analyzed.The snow and soil stratification were selected to study the effects of different types of snow,soil surfaces with different humidity,and characteristic parameters of rough surfaces on the scattering of stratified rough surfaces.The effect of composite scattering in the case of delamination is further discussed in conjunction with the target.