Matching Items (2)
Description
Scattering from random rough surface has been of interest for decades. Several
methods were proposed to solve this problem, and Kirchho approximation (KA)
and small perturbation method (SMP) are among the most popular. Both methods
provide accurate results on rst order scattering, and the range of validity is limited
and cross-polarization scattering coecient is zero for these two methods unless these
two methods are carried out for higher orders. Furthermore, it is complicated for
higher order formulation and multiple scattering and shadowing are neglected in these
classic methods.
Extension of these two methods has been made in order to x these problems.
However, it is usually complicated and problem specic. While small slope approximation
is one of the most widely used methods to bridge KA and SMP, it is not easy
to implement in a general form. Two scale model can be employed to solve scattering
problems for a tilted perturbation plane, the range of validity is limited.
A new model is proposed in this thesis to deal with cross-polarization scattering
phenomenon on perfect electric conducting random surfaces. Integral equation
is adopted in this model. While integral equation method is often combined with
numerical method to solve the scattering coecient, the proposed model solves the
integral equation iteratively by analytic approximation. We utilize some approximations
on the randomness of the surface, and obtain an explicit expression. It is shown
that this expression achieves agreement with SMP method in second order.
methods were proposed to solve this problem, and Kirchho approximation (KA)
and small perturbation method (SMP) are among the most popular. Both methods
provide accurate results on rst order scattering, and the range of validity is limited
and cross-polarization scattering coecient is zero for these two methods unless these
two methods are carried out for higher orders. Furthermore, it is complicated for
higher order formulation and multiple scattering and shadowing are neglected in these
classic methods.
Extension of these two methods has been made in order to x these problems.
However, it is usually complicated and problem specic. While small slope approximation
is one of the most widely used methods to bridge KA and SMP, it is not easy
to implement in a general form. Two scale model can be employed to solve scattering
problems for a tilted perturbation plane, the range of validity is limited.
A new model is proposed in this thesis to deal with cross-polarization scattering
phenomenon on perfect electric conducting random surfaces. Integral equation
is adopted in this model. While integral equation method is often combined with
numerical method to solve the scattering coecient, the proposed model solves the
integral equation iteratively by analytic approximation. We utilize some approximations
on the randomness of the surface, and obtain an explicit expression. It is shown
that this expression achieves agreement with SMP method in second order.
ContributorsCao, Jiahao (Author) / Pan, George (Thesis advisor) / Balanis, Constantine A (Committee member) / Cochran, Douglas (Committee member) / Arizona State University (Publisher)
Created2017
Description
We present fast and robust numerical algorithms for 3-D scattering from perfectly electrical conducting (PEC) and dielectric random rough surfaces in microwave remote sensing. The Coifman wavelets or Coiflets are employed to implement Galerkin’s procedure in the method of moments (MoM). Due to the high-precision one-point quadrature, the Coiflets yield fast evaluations of the most off-diagonal entries, reducing the matrix fill effort from O(N^2) to O(N). The orthogonality and Riesz basis of the Coiflets generate well conditioned impedance matrix, with rapid convergence for the conjugate gradient solver. The resulting impedance matrix is further sparsified by the matrix-formed standard fast wavelet transform (SFWT). By properly selecting multiresolution levels of the total transformation matrix, the solution precision can be enhanced while matrix sparsity and memory consumption have not been noticeably sacrificed. The unified fast scattering algorithm for dielectric random rough surfaces can asymptotically reduce to the PEC case when the loss tangent grows extremely large. Numerical results demonstrate that the reduced PEC model does not suffer from ill-posed problems. Compared with previous publications and laboratory measurements, good agreement is observed.
ContributorsZhang, Lisha (Author) / Pan, George (Thesis advisor) / Diaz, Rodolfo (Committee member) / Aberle, James T., 1961- (Committee member) / Yu, Hongbin (Committee member) / Arizona State University (Publisher)
Created2016