| The nearshore environment is usually composed of land and ocean surfaces with different characteristics.Therefore,the radar echoes from the nearshore electromagnetic environment will contain more complex land-oceanic clutter components,which poses challenges to nearshore environment radar target detection.By modeling the electromagnetic scattering of the typical nearshore land-oceanic environment,we can further understand the electromagnetic scattering characteristics of the nearshore land-oceanic environment,and provide a theoretical basis for target detection a nd recognition in complex land and ocean backgrounds.This thesis studies and analyzes the geometric modeling and electromagnetic scatter ing characteristics of the nearshore land-oceanic environment.The main research work is reflected in the fol owing three aspects: 1.The geometric modeling method of random rough surface is analyzed.First,the common statistical parameters and power spectrum models of the rough surface are described,and two geometric modeling methods of the rough surface are introduced in detail,namely the linear superposition method and the linear filtering method.Secondly,a linear filtering method was used to generate a linear ocean surface and a nonlinear ocean surface,and the geometric characteristics of the two ocean surfaces were compared.Finally,a geometric model of the land conforming to the exponential distribution and gaussian distribution is established,and the influence of parameter changes on the ground fluctuation is analyzed.2.Based on the electromagnetic scattering model of the rough surface,the electromagnetic scattering characteristics of the nearshore ocean surface and land are studied.The electromagnetic modeling advantages of the semi-deterministic facet scattering model and the small slope approximation method are compared in turn,and the small slope approximation method is applied to the study of the electromagnetic scattering characteristics of the non-linear ocean surface in near-shore limited deep water.The radar parameters and the ocean environment are analyzed.The influence of parameters on the electromagnetic scattering characteristics of the nearshore ocean surface.Based on the characteristics of the nearshore environment,the parameters of soil moisture,soil temperature and clay content on the soil dielectric constant were studied influences.Through electromagnetic modeling,the influence of different environmental parameters on the electromagnetic scattering characteristics of the nearshore land is discussed.3.Based on the sigmod function,the composite rough surface transit ion problem is modulated,and three kinds of composite rough surfaces,including straight boundary,crescent boundary,and canyon boundary are simulated.A linear modulation function is used to smoothly transition the boundary between the land and the ocean in the nearshore environment,and a representative linear composite model of land and ocean is obtained through simulation.On the basis of this geometric model,a small slope approximation method was used to focus on the electromagnetic wave polarizatio n mode,land root mean square height,related length,soil humidity,wind speed above the ocean surface,wind direction angle and other related parameters.The influence of scattering characteristics and a reasonable analysis of the scattering results. |
