An inverse scattering problem of estimating the surface impedance for an inhomogeneous half-space is investigated. By virtue of the fact that the far field representation contains the spectral function of the scattered field, complex values of the function are estimated from a set of absolute values of the far field. An approximate function for the spectral function is reconstructed from the estimated complex values by the least-squares sense. The surface impedance is estimated through calculating the field on the surface of the half-space expressed by the inverse Fourier transform. Numerical examples are given and the accuracy of the estimation is discussed.

The diffraction of a plane electromagnetic wave by an impedance wedge whose boundary is described in terms of the skew coordinate systems is treated by using the Wiener-Hopf technique. The problem is formulated in terms of the simultaneous Wiener-Hopf equations, which are then solved by using a factorization and decomposition procedure and introducing appropriate functions to satisfy the edge condition. The exact solution is expressed through the Maliuzhinets functions. By deforming the integration path of the Fourier inverse transform, which expresses the scattered field, the expressions of the reflected field, diffracted field and the surface wave are obtained. The numerical examples for these fields are given and the characteristics of the surface wave are discussed.

The two-dimensional scattering problem of electromagnetic waves by a perfectly conducting wedge is analyzed by means of the Wiener-Hopf technique together with the formulation using the partition of scatterers. The Wiener-Hopf equations are derived on two complex planes. Investigating the mapping between these complex planes and introducing the appropriate functions which satisfy the edge condition of the wedge, the solutions of these equations are obtained by the decomposition procedure of functions. By deforming the integration path of the Fourier inverse transform, it is found that the representation of the scattered wave is in agreement with the integral representation using the Sommerfeld contours.

An inverse scattering problem of estimating the reflection coefficient and the surface impedance from two sets of absolute values of the near field with periodic change is investigated. The problem is formulated in terms of a nonlinear simultaneous equations which is derived from the relation between the two sets of absolute values and the field defined by a finite summation of the modal functions by applying the Fourier analysis. The reflection coefficient is estimated by solving the equations by Newton's method through the successive algorithm with the increment of the number of truncation in the summation one after another. Numerical examples are given and the accuracy of the estimation is discussed.

The electromagnetic scattering of a plane wave by an inhomogeneous plane whose surface impedance changes locally on the plane is treated. A boundary-value problem is formulated to describe the scattering phenomenon, in which the boundary condition depends on the surface impedance of the plane. Application of the Fourier transform derives an integral equation, which is approximately solved by the method of least-squares. From the solution of the equation, the scattered field is obtained by the inverse Fourier transform. By the use of the incomplete Lipschitz-Hankel integral for the computation of the field, numerical examples are given and the scattering phenomenon is discussed.

The problem of two-dimensional scattering of electromagnetic waves by a grating with several strips arbitrarily oriented in one period is analyzed by means of the Wiener-Hopf technique together with the formulation using the concept of the mutual field. A formulation for the analysis of multiple scattering from the grating is based on the representation of the scattered field by a grating composed of one strip in one period. The Wiener-Hopf equations and a representation of the scattered wave are obtained. The characteristic of the sampling function is used to expand the unknown function associated with the field on the strip into a series, and then the Wiener-Hopf equations are reduced to a set of simultaneous equations. For evaluation of the convergence and the errors in the numerical results, the relative error with respect to the extrapolated value and the square error for satisfaction of the boundary condition are computed. From numerical comparison of the present method with other various methods, it is found that the present method provides us accurate results. Some numerical examples of the reflection coefficients are presented for the reflection grating and transmission gratings.

The problem of transient scattering caused by abrupt extinction of a terminative conducting screen in a waveguide is considered. First, a boundary-value problem is formulated to describe the transient phenomena, the problem in which the boundary condition depends on time. Then, application of the Fourier transformation with respect to time derives a Wiener-Hopf-type equation, which is solved by a commonly known decomposition procedure. The transient fields are obtained through the deformation of the integration path for the inverse transformation and the results are represented in terms of the incomplete Lipschitz-Hankel integrals. Numerical examples showing typical transient phenomena are attached.

The two-dimensional scattering problem of electromagnetic waves by a grating composed of two arbitrarily oriented strips in one period is analyzed by means of the formulation using the mutual field. A formulation is presented for the analysis of multiple scattering by the grating by means of the representation of the scattered field by a grating composed of one strip in one period. The Wiener-Hopf equations to be satisfied by each scattered field and the representation of scattered wave based on the solution to these equation are obtained. Since the width of the strips in the grating is finite, it is difficult to carry out rigorously the decomposition in the solution of the Wiener-Hopf equations. The characteristic of the sampling function is used for expansion of the unknown function into a series so that the Wiener-Hopf equations are reduced to a set of simultaneous equations. For evaluation of the convergence and the errors in the results, the relative error with respect to the extrapolated value and the square error for satisfaction of the boundary condition are numerically computed. From numerical comparison of the present method with other various methods, it is found that the present method provides us accurate results. Some numerical examples on the reflection coefficient are presented for the reflection and transmission gratings.

The transient phenomenon of electromagnetic waves caused by a time dependent resistive screen in a waveguide is treated. A boundary-value problem is formulated to describe the phenomena, in which the resistivity of the screen varies from one steady state to another in dependence on time. Application of Fourier analysis derives an integral equation, which is approximately solved by the method of least-squares. From the solution of the equation, the transient field is obtained by the inverse Fourier transform. By the use of the incomplete Lipschitz-Hankel integral for the computation of the field, numerical examples showing typical transient phenomenon are attached.

The cause-and-effect relation between plasmon-resonance absorption and surface wave in a sinusoidal metal grating is investigated. By introducing an equivalent impedance model, similar to an equivalent circuit on an electric circuit, which is an impedance boundary value problem on the fictitious surface over the grating, we estimate the surface wave from the eigen field of the model by using the resonance property of the scattered field. Through numerical examples, we illustrate that the absorption in the grating occurs in the condition of exciting the surface wave along the model, and the real part of the surface impedance is negative on about half part of the fictitious surface in the condition.

The transient phenomenon of electromagnetic waves caused by a time dependent resistive screen in a waveguide is treated by using Wiener-Hopf technique. A boundary-value problem is formulated to describe the phenomenon, in which the resistivity of screen varies from infinite to zero in dependence on time. Application of the Fourier transformation with respect to time derives a Wiener-Hopf equation, which is solved by a commonly known decomposition procedure. The transient field is derived from the solution of the equation in terms of the Fourier inverse transform. By using the incomplete Lipschitz-Hankel integral for the computation of the field, numerical examples are given and the transient phenomenon is discussed.