In this paper, we provide a review of the different approaches used for target decomposition theory in radar polarimetry. We classify three main types of theorem; those based on the Mueller matrix and Stokes vector, those using an eigenvector analysis of the covariance or coherency matrix, and those employing coherent decomposition of the scattering matrix. We unify the formulation of these different approaches using transformation theory and an eigenvector analysis. We show how special forms of these decompositions apply for the important case of backscatter from terrain with generic symmetries.

A review of target decomposition theorems in radar polarimetry

Singular Integral Equations. By N.I. Muskhelishvili. Translated fromthe 2nd Russian edition by J.R.M. Radok. Pp. 447. F1. 28.50. 1953. (Noordhoff, Groningen)

We present an algorithm that decomposes a Mueller matrix into a sequence of three matrix factors: a diattenuator, followed by a retarder, then followed by a depolarizer. Those factors are unique except for singular Mueller matrices. Based on this decomposition, the diattenuation and the retardance of a Mueller matrix can be defined and computed. Thus this algorithm is useful for performing data reduction upon experimentally determined Mueller matrices.

Interpretation of Mueller matrices based on polar decomposition

A direct approach to exact solutions of nonlinear partial differential equations is proposed, by using rational function transformations. The new method provides a more systematical and convenient handling of the solution process of nonlinear equations, unifying the tanh-function type methods, the homogeneous balance method, the exp-function method, the mapping method, and the F -expansion type methods. Its key point is to search for rational solutions to variable-coefficient ordinary differential equations transformed from given partial differential equations. As an application, the construction problem of exact solutions to the 3 + 1 dimensional Jimbo–Miwa equation is treated, together with a Backlund transformation.

https://shell.cas.usf.edu/~wma3/MaL-CSF2009.pdf

A transformed rational function method and exact solutions to the 3+1 dimensional Jimbo–Miwa equation

An overview is given over some of the most widely used numerical techniques for solving the electromagnetic scattering problem that start from rigorous electromagnetic theory. In particular, the theoretical foundations of the separation of variables method, the finite-difference time-domain method, the finite-element method, the method of lines, the point matching method, the method of moments, the discrete dipole approximation, and the null-field method (or extended boundary condition method) are reviewed, and the advantages and disadvantages of the different methods are discussed. Aspects concerning the T matrix formulation and the surface Green's function formulation of the electromagnetic scattering problem are addressed.

Numerical methods in electromagnetic scattering theory

The inverse scattering transform (IST) as a tool to solve the initial-value problem for the focusing nonlinear Schrodinger (NLS) equation with non-zero boundary values ql/r(t)≡Al/re−2iAl/r2t+iθl/r as x → ∓∞ is presented in the fully asymmetric case for both asymptotic amplitudes and phases, i.e., with Al ≠ Ar and θl ≠ θr. The direct problem is shown to be well-defined for NLS solutions q(x, t) such that q(x,t)−ql/r(t)∈L1,1(R∓) with respect to x for all t ⩾ 0, and the corresponding analyticity properties of eigenfunctions and scattering data are established. The inverse scattering problem is formulated both via (left and right) Marchenko integral equations, and as a Riemann-Hilbert problem on a single sheet of the scattering variables λl/r=k2+Al/r2, where k is the usual complex scattering parameter in the IST. The time evolution of the scattering coefficients is then derived, showing that, unlike the case of solutions with equal amplitudes as x → ±∞, here both reflection and transmission coefficients have ...

The inverse scattering transform for the focusing nonlinear Schrödinger equation with asymmetric boundary conditions

Simple eigenvalue tests are given to ascertain that a given real 4×4 matrix transforms the four‐vector of Stokes parameters of a beam of light into the four‐vector of Stokes parameters of another beam of light, and to determine whether a given 4×4 matrix is a weighted sum of pure Mueller matrices. The latter result is derived for matrices satisfying a certain symmetry condition. To derive these results indefinite inner products are applied.

/pdf/an-eigenvalue-criterion-for-matrices-transforming-stokes-1xx5iyfiov.pdf

An eigenvalue criterion for matrices transforming Stokes parameters

Scattering matrices describe the transformation of the Stokes parameters of a beam of radiation upon scattering of that beam. The problems of testing scattering matrices for scattering by one particle and for single scattering by an assembly of particles are addressed. The treatment concerns arbitrary particles, orientations and scattering geometries. A synopsis of tests that appear to be the most useful ones from a practical point of view is presented. Special attention is given to matrices with uncertainties due, e.g., to experimental errors. In particular, it is shown how a matrix E mod can be constructed which is closest (in the sense of the Frobenius norm) to a given real 4 × 4 matrix E such that E mod is a proper scattering matrix of one particle or of an assembly of particles, respectively. Criteria for the rejection of E are also discussed. To illustrate the theoretical treatment a practical example is treated. Finally, it is shown that all results given for scattering matrices of one particle are applicable for all pure Mueller matrices, while all results for scattering matrices of assemblies of particles hold for sums of pure Mueller matrices.

Testing scattering matrices: A compendium of recipes

The structure of matrices that represent a linear transformation of the Stokes parameters of a beam of light into the Stokes parameters of another beam of light is investigated by means of the so‐called Stokes criterion. This holds that the degree of polarization of a beam of light can never be changed into a number larger than unity. Several general properties are derived for matrices satisfying the Stokes criterion. These are used to establish conditions for the elements of such matrices. Conditions that are either necessary, or sufficient or both are presented. General 4×4 matrices are treated and a number of special cases is worked out analytically. Several applications are pointed out.

/pdf/structure-of-matrices-transforming-stokes-parameters-2gy0b3bdih.pdf

Structure of matrices transforming Stokes parameters

We study the abstract differential equation\(T\frac{{\partial f}}{{\partial x}} + Af = 0\) on a Hilbert space H, which represents a variety of different kinetic equations. T is assumed bounded and self-adjoint on H, and A (unbounded) positive self-adjoint and Fredholm. For partial range boundary conditions and 0≤x<∞, we prove existence and (non-) uniqueness theorems and give representations of the solution. Various examples from neutron transport, radiative transfer of polarized and unpolarized light, and electron transport are given.

C. V. M. van der Mee

Papers

The inverse scattering transform for the focusing nonlinear Schrödinger equation with asymmetric boundary conditions

An eigenvalue criterion for matrices transforming Stokes parameters

Testing scattering matrices: A compendium of recipes

Structure of matrices transforming Stokes parameters

Generalized kinetic equations