Numerical Simulations of Emission and Bistatic Scattering from Soils with Rough Surfaces of Exponential Correlation Functions

Conference Paper · January 2008with3 Reads
DOI: 10.1109/IGARSS.2008.4780041 · Source: DBLP
Conference: IEEE International Geoscience & Remote Sensing Symposium, IGARSS 2008, July 8-11, 2008, Boston, Massachusetts, USA, Proceedings
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.
  • [Show abstract] [Hide abstract] ABSTRACT: A UV method with multilevel partitioning (UVMLP) is developed to solve electromagnetic problem. In this paper we demonstrate the technique to treat electromagnetic problem for large surface in a two-dimensional (2-D) problem. Using the multilevel partitioning (MLP), the decomposition preprocessing, and the matrix vector multiplication require CPU of O(N logN) per iteration with a smaller constant factor for matrix column multiplication than decomposition. The memory requirement is of O(N logN). We demonstrate the technique for a rough surface scattering problem with surface length up to 13,000 wavelengths and RMS height up to ten wavelengths. Computations are based on using PC with a single Pentium 4-2.4 GHz processor and 1 G RAM. For the case of 65,536 unknowns, it requires about CPU from 3.3 to 5.33 s per iteration and a total CPU of 3.9-14.3 min with 49-146 conjugate gradient iterations.
    Full-text · Article · Oct 2004
  • [Show abstract] [Hide abstract] ABSTRACT: The effects of a random rough surface between dielectric and lossy conductive medium on power absorption are analyzed by considering incident plane waves impinging on the interface. We use two methods to formulate and solve the 2-D problem: the two-media small perturbation method to second order (SPM2) and the numerical system transfer operator matrix method, referred to as T-matrix method. The two methods are in agreement within the regimes of validity. The results show significant difference between absorption of a rough surface and that of a smooth surface. Surface fields are further examined numerically. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 7–13, 2007; Published online in Wiley InterScience ( DOI 10.1002/mop.22023
    Article · Jan 2007
  • [Show abstract] [Hide abstract] ABSTRACT: 1] A procedure is developed for combining efficiently the multilevel UV method with the sparse matrix canonical grid (SMCG) method in the computation of three-dimensional (3-D) wave scattering from random rough surface. It handles near-and intermediate-field interactions by the multilevel UV method and far-field interactions by the SMCG method. This hybrid UV/SMCG method removes the large memory requirement of both the UV method in the far field and the SMCG method in the near field. The computational complexity for the hybrid method is O(NlogN). The tradeoffs in computer memory requirement and CPU time between the UV part and the SMCG part are examined for Gaussian random rough surfaces with Gaussian correlation function and with exponential correlation function. For a surface area of 44 Â 44 square wavelengths with RMS of 1 wavelength and 123,904 surface unknowns, the UV/SMCG method requires CPU of 52.2 s per iteration with total CPU of 46.6 min for 22 iterations on a single processor of CPU speed of 2.66 GHz. Citation: Xu, P., and L. Tsang (2005), Scattering by rough surface using a hybrid technique combining the multilevel UV method with the sparse matrix canonical grid method, Radio Sci., 40, RS4012, doi:10.1029/2005RS003242.
    Full-text · Article · Aug 2005
  • [Show abstract] [Hide abstract] 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.
    Full-text · Article · Oct 2004
  • [Show abstract] [Hide abstract] ABSTRACT: Thesis (Ph. D.)--University of Washington, 2003 In the first part of the work, we developed coding for large-scale computation to solve 3-dimensional microwave scattering problem. Maxwell integral equations are solved by using MoM with RWG basis functions in conjunction with fast computation algorithms. The cost-effective solutions of parallel and distributed simulation were implemented on a low cost PC cluster, which consists of 32 processors connected to a fast Ethernet switch. More than a million of surface current unknowns were solved at unprecedented speeds. Accurate simulations of emissivities and bistatic coefficients from ocean and soil were achieved. Exponential correlation function and ocean spectrum are implementd for generating soil and ocean surfaces. They have fine scale features with large rms slope. The results were justified by comparison with numerical results from original code, which is based on pulse basis function, and from analytic methods like SPM, and also with experiments. In the second part of the work, fully polarimetric microwave emissions from wind-generated foam-covered ocean surfaces were investigated. The foam is treated as densely packed air bubbles coated with thin seawater coating. The absorption, scattering and extinction coefficients were calculated by Monte Carlo simulations of solutionsof Maxwell equations of a collection of coated particles. The effects of boundary roughness of ocean surfaces were included by using the second-order small perturbation method (SPM) describing the reflection coefficients between foam and ocean. An empirical wave-number spectrum was used to represent the small-scale wind-generated sea surfaces. The theoretical results of four Stokes brightness temperatures with typical parameters of foam in passive remote sensing at 10.8 GHz, 19.0 GHz and 36.5 GHz were illustrated. The azimuth variations of polarimetric brightness temperature were calculated. Emission with various wind speed and foam layer thickness was studied. The results were also compared with those based on Quasi-Crystalline Approximation (QCA).
    Article · Jan 2003 · IEEE Transactions on Geoscience and Remote Sensing
  • [Show abstract] [Hide abstract] ABSTRACT: Bistatic scattering and emissivities of surfaces with exponential correlation functions are studied numerically for 2-D geometries in a numerical Maxwell model with 2-D simulations. Surfaces with exponential correlation functions are important for the active and passive microwave remote sensing of land surfaces. Because of the fine-scale features with large slopes of such surfaces, numerical accuracy, which is particularly important for the calculation of emissivity in passive remote sensing, is ensured by a variety of procedures in this paper. The rooftop function and Galerkin's method with numerical integration of near-field impedance matrix elements are used. Cubic spline interpolation is employed to connect knots on random rough surfaces. Numerical accuracy convergence tests are performed for numerical solutions of Maxwell equations by varying the number of points from 13 to 103 points per wavelength in the dielectric medium corresponding to 50-400 points per free wavelength. Surface lengths of up to 100 and 200 free wavelengths and root mean square heights of up to 0.4 and 0.8 free wavelengths, respectively, are used at 5 and 10 GHz to capture all the essential features. Because of the large number of surface unknowns (up to 80 000), the multilevel UV method is further used to accelerate the matrix equation solver. Numerical results are illustrated for both bistatic scattering and emissivities as functions of frequencies and incidence and scattering angles for cases of interests in microwave remote sensing. Comparisons are made with the second-order small perturbation method and Kirchhoff's approximation to reestablish the regimes of validity of these methods
    Full-text · Article · Feb 2007
Show more
January 2001 · Waves in Random Media
This paper is a companion to our previous contribution deriving a new approximate bistatic model for electromagnetic scattering from perfectly conducting rough surfaces. We evaluate this model numerically and compare it with an `exact' numerical solution of the scattering problem. This comparison shows good agreement between our approximation and numerical solution for a wide range of incident... [Show full abstract]
July 2006
According to simulation analysis of AlEM, there is a good linear relationship between emissivity and soil moisture tinder given roughness. The normalized difference between emissivity of 18.7GHz and 10.7GHz can eliminate partly the influence of roughness and the R-Square is about 0.98. This paper intends to propose an algorithm for retrieving soil moisture by brightness temperature from AMSR-E... [Show full abstract]
August 2002 · International Journal of Remote Sensing · Impact Factor: 1.65
The inverse problem of estimating soil moisture from vegetated and non-vegetated terrain is investigated using a passive microwave technique. The radiometer response at L-band is modelled by the Peake's approach that involves the integration of bistatic scattering coefficients to calculate surface emissivity. For vegetated terrain, a discrete scatter model employing the distorted Born... [Show full abstract]
Discover more