Numerical Simulations of Emission and Bistatic Scattering from Soils with Rough Surfaces of Exponential Correlation Functions.
ABSTRACT In this paper, we report on the polarimetric active and passive microwave remote signatures for exponential correlation function surfaces. Applications are in soil moisture problems at the frequencies L, C and X band. We use the same physical parameters of rms heights and correlation lengths at the three frequencies. Results for 2D case with rms height up to 2 wavelengths at X band are shown. The hybrid UV-SMCG method for RWG basis is also used to accelerate MoM solution. Comparisons are made with SPM, KA and AIEM predictions. We also compare backscattering between horizontal and vertical polarization cases at different rms heights with exponential correlation. At small rms height, the backscattering for vertical polarization case is larger than that for horizontal polarization case. On the other hand, at large rms height, the backscattering for horizontal polarization case is larger.
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ABSTRACT: 1] A UV multilevel partitioning method (UV-MLP) is developed to solve scalar wave three-dimensional (3-D) scattering problem. The method consists of setting up a table of transmitting and receiving block size and their separation using fast coarse-coarse sampling. For a specific scattering problem with given geometry, the scattering structure is partitioned into multilevel blocks. By looking up the rank in the static problem, the impedance matrix for a given transmitting and receiving block is expressed into a product of U and V matrix. In this paper the method is illustrated by applying to a 3-D scattering problem of random nonpenetrable rough surface. The cases of Dirichelt and Neumann boundary conditions are treated. Numerical simulation results are illustrated. For 65,536 boundary unknowns on a rough surface, and using a single processor of 2.66 GHz, it takes about 34 CPU min and 1.8 Gb of memory to compute the solution using conjugate gradient iterations and multilevel UV to accelerate the matrix-column vector multiplication. (2004), Wave scattering with UV multilevel partitioning method: 2. Three-dimensional problem of nonpenetrable surface scattering, Radio Sci., 39, RS5011, doi:10.1029/2003RS003010.Radio Science 01/2004; 39(5). · 1.00 Impact Factor
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ABSTRACT: This paper presents a model of microwave emissions from rough surfaces. We derive a more complete expression of the single-scattering terms in the integral equation method (IEM) surface scattering model. The complementary components for the scattered fields are rederived, based on the removal of a simplifying assumption in the spectral representation of Green's function. In addition, new but compact expressions for the complementary field coefficients can be obtained after quite lengthy mathematical manipulations. Three-dimensional Monte Carlo simulations of surface emission from Gaussian rough surfaces were used to examine the validity of the model. The results based on the new version (advanced IEM) indicate that significant improvements for emissivity prediction may be obtained for a wide range of roughness scales, in particular in the intermediate roughness regions. It is also shown that the original IEM produces larger errors that lead to tens of Kelvins in brightness temperature, which are unacceptable for passive remote sensing.IEEE Transactions on Geoscience and Remote Sensing 02/2003; · 3.47 Impact Factor
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ABSTRACT: In the numerical Maxwell-equation model (NMM3D) of rough-surface scattering, we solve Maxwell equations in three dimensions to calculate emissivities for applications in passive microwave remote sensing of soil and ocean surfaces. The difficult cases for soil surfaces are with exponential correlation functions when the surfaces have fine-scale structures of large slopes. The difficulty for ocean surfaces is that because the emissivities are close to that of a flat surface, the emissivities have to be calculated accurately to correctly assess the rough-surface effects. In this paper, the accuracies of emissivity calculations are improved by using Rao-Wilton-Glisson basis functions. We further use sparse matrix canonical method to solve the matrix equation of Poggio-Miller-Chang-Harrington-Wu integral equations. Energy conservation checks are provided for the simulations. Comparisons are made with results from the pulse basis function. Numerical results are illustrated for soil and ocean surfaces respectively with exponential correlation function and ocean spectrum. The emissivities of soil are illustrated at both L- and C-bands and at multiple incidence angles for the same physical roughness parameters. The brightness temperatures for ocean surfaces are illustrated for cases with various wind speeds. We compare results with those from the sparse matrix methods. Comparisons are also made with experimental emissivity measurements of soil surfaces. Parallel computation is also implemented. Lookup tables of emissivities based on NMM3D are provided.IEEE Transactions on Geoscience and Remote Sensing 09/2004; · 3.47 Impact Factor