Study On The Mechanism And Model Of Microwave Scattering On Random Rough Surfaces

The research on scattering properties of random rough surfaces is an important basis for parameter inversion of ground and sea surface in microwave remote sensing.This paper mainly studies the backscattering characteristics of random rough surface with roughness and macroscopic dielectric constant as main parameters.The main research is divided into four parts:(1)A random rough surface model is established by using the band limits Weierstrass-Mandelbrot fractal function.The parameters of the model are quantitatively analyzed.The relationship between the fractal parameters and the statistical parameters of the random rough surface is established.By adjusting the input fractal parameters,random rough surfaces of different roughness(root mean square height and related length)are obtained.Finally,the error analysis of this method is obtained.(2)The random rough surface is constructed as a soil model with penetration depth.Simulation calculation is performed in the electromagnetic numerical simulation software.This paper uses two kinds of electromagnetic simulation software-FEKO and EMPIRErespectively using multi-layer fast multipole algorithm and finite difference time domain algorithm.As the angle of incidence becomes larger,the artificial diffraction of the edges of the rough surface becomes increasingly unignorable.The tapered wave model was established in FEKO.It makes the electric field strength on the rough surface appear weak from middle to edge.That effectively avoids edge diffraction.In the EMPIRE,a perfectly matched layer is provided to absorb the reflected wave and the downward transmitted wave.The numerical simulation of the rough surface with different system parameters and random rough surface parameters was performed and the scattering results were analyzed.(3)The band-limited fractal function applied when constructing a random rough surface has the form of a trigonometric series and can be divided into a series of trigonometric functions with different periods.Using the extended boundary condition method to scatter the fractal rough surface,the total scattered field is obtained.Then,the extended boundary condition method is applied to the surface generated by each trigonometric function component to obtain the scattering result of each surface.The result is vector superimposed on the scattering results of each component.The result of the superposition of the scattered field is compared with the above total scattering field.It is found that there is a certain degree of consistency.Through this method,the analytical calculation of the scattered field can be simplified.Finally,the FDTD numerical calculation results are used for auxiliary verification.(4)The dielectric constant,as an important attribute of the object,influences the scattering properties of the rough surface.The materials needed for the experiment(pure water,dry soil,river sand,charcoal powder)were collected and processed and mixed at a certain volume ratio or mass ratio.The coaxial probe method and the waveguide method were studied.After the vector network analyzer system was calibrated,the mixture was measured.The original experimental data was processed to obtain the experimental results.Finally,a macroscopic dielectric constant model of the two-phase mixture was established by means of function fitting.