The present paper gives a new formulation for rough surface scattering in terms of a stochastic integral equation which can be dealt with by means of stochastic functional approach. The random surface is assumed to be infinite and a homogeneous Gaussian random process. The random wave field is represented in the stochastic Floquet form due to the homogeneity of the surface, and in the non-Rayleigh form consisting of both upward and downward going scattered waves, as well as in the extended Voronovich form based on the consideration of the level-shift invariance. The stochastic integral equations of the first and the second kind are derived for the unknown surface source function which is a functional of the derivative or the increment of the surface profile function. It is also shown that the inhomogeneous term of the stochastic integral equation of the second kind automatically gives the solution of the Kirchhoff approximation for infinite surface.

This paper deals with two different quantitative inversion algorithms for reconstructing the complex permittivity profile of bounded inhomogeneous objects from measured scattered field data. The first algorithm involves an imaging method with single frequency excitation and multiincidence illumination and the second algorithm involves a method with synthetic pulse (multifrequency mode) excitation for objects surrounded by freespace or buried in stratified half-space media. Transmission or reflection imaging protocols are considered depending on aimed applications: microwave imaging in free-space from far-field data for target identification, microwave imaging from near-field data for nondestructive testing (NDT), microwave tomography of buried objects for mine detection and localization, civil engineering and geophysical applications. And Edge-Preserving regularization scheme leading to a significant enhancement in the image reconstructions is also proposed. The methods are illustrated with synthetic and experimental data.

In the paper the well known ray method is generalized to the case of the inhomogeneous chiral electromagnetic media. The electromagnetic field decompose in a chiral medium into two components with different propagation velocities. In the paper each of these components are presented in the form of ray expantions. The coefficients of these expantions are calculated in the ray coordinates which are attributed to the characteristics of eikonal equations. The leading and admixed components of the electromagnetic vectors are investigated and the polarization effects for both field components are analysed.

In this paper, we illustrate the analysis of microstrip structures with a large number of unknowns using the sparse-matrix/canonical grid method. This fast Fourier thansform (FFT) based iterative method reduces both CPU time and computer storage memory requirements. We employ the Mixed-Potential Integral Equation (MPIE) formulation in conjunction with the RWG triangular discretization. The required spatial-domain Green's functions are obtained efficiently and accurately using the Complex Image Method (CIM). The impedance matrix is decomposed into a sparse matrix which corresponds to near interactions and its complementary matrix which corresponds to far interactions among the subsectional current elements on the microstrip structures. During the iterative process, the near-interaction portion of the matrix -vector multiplication is computed directly as the conventional MPIE formulation. The far-interaction portion of the matrix-vector multiplication is computed indirectly using fast Fourier transforms (FFTs). This is achieved by a Taylor series expansion of the Green's function about the grid points of a uniformly-spaced canonical grid overlaying the triangular discretization.

Electromagnetic field diffracted by conducting circular disk and circular hole in the conducting plate is formulated by the method of Kobayashi potential. The field is expressed by linear combination of functions which satisfy the required boundary conditions except on the disk or hole. Thus the functions may be regarded as eigen functions of the configuration. By imposing the remaining boundary conditions, we can derive the matrix equations for the expansion coefficients. It may be verified readily that each eigen function satisfies edge conditions for induced current on the disk and for aperture field distribution on the hole. It may also be verified that the solutions for the disk and the hole satisfy Babinet's principle. Matrix elements of the equations for the expansion coefficients are given by two kinds of infinite integrals and the series solutions for these integrals are derived. The validity of these expressions are verified numerically by comparing with the results obtained from direct numerical integrations.

In this paper, a quite general systematic procedure is presented for defining incremental field contributions, that may provide effective tools for describing a wide class of scattering and diffraction phenomena at any aspect, whthin a unitary, self-consistent framework. This is based on a generalization of the localization process for cylindrical canonical problems with elementary source illumination and arbitrary observation aspects. In particular, it is shown that the spectral integral formulation of the exact solution may also be represented as a spatial integral convolution along the axis of the cylinder. Its integrand is then directly used to define the relevant incremental field contribution. This procedure, that will be referred to as a ITD (Incremental Theory of Diffraction) Fourier transform convolution localization process, is explicitly applied to both wedge and circular cylinder canonical configurations, to define incremental diffiraction and scattering contributions, respectively. These formulations are asymptotically approximated to find closed form high-frequency expression for the incremental field contributions. This generalization of the ITD lacalization process may provide a quite general, systematic procedure to find incremental field contributions that explicitly satisfy reciprocity and naturally lead to the UTD ray field representation, when it is applicable.

This paper deals with a probabilistic formulation of the diffraction and scattering of a plane wave from a periodic surface randomly deformed by a binary sequence. The scattered wave is shown to have a stochastic Floquet's form, that is a product of a periodic stationary random function and an exponential phase factor. Such a periodic stationary random function is then represented in terms of a harmonic series representation similar to Fourier series, where `Fourier coefficients' are mutually correlated stationary processes rather than constants. The mutually correlated stationary processes are written by binary orthogonal functionals with unknown binary kernels. When the surface deformations are small compared with wavelength, an approximate solution is obtained for low-order binary kernels, from which the scattering cross section, coherently diffracted power and the optical theorem are numerically calculated and are illustrated in figures.

This paper deals with the scattering and diffraction of a plane wave by a randomly rough half-plane by three tools: the small perturbation method, the Wiener-Hopf technique and a group theoretic consideration based on the shift-invariance of a homogeneous random surface. For a slightly rough case, the scattered wavefield is obtained up to the second-order perturbation with respect to the small roughness parameter and represented by a sum of the Fresnel integrals with complex arguments, integrals along the steepest descent path and branch-cut integrals, which are evaluated numerically. For a Gaussian roughness spectrum, intensities of the coherent and incoherent waves are calculated in the region near the edge and illustrated in figures, in terms of which several characteristics of scattering and diffraction are discussed.

The integral kernel expansion method is applied to an analysis of scattering of magnetostatic forward volume waves (MSFVWs) by an array with any number of metal strips. In this method, first the integral kernel of the Fourier integral is expanded in terms of orthogonal polynomials to obtain moment equations. Then a system of algebraic equations is derived by applying the Galerkin's method. In the process, interaction between strips is naturally taken into account and real current distributions on the strips are determined such that boundary conditions are satisfied. Calculus confirmation through the energy conservation principle shows that numerical results are quite satisfactory. A comparison shows that theoretical results are in good agreement with experimental ones except the vicinity of lower and upper limits of the MSFVW band. It is shown that an infinite number of propagation modes is excited even if a wave of single mode is incident. Dependence of the scattering on dimension of arrays and on frequency and mode of an incident wave is obtained.

Characterization of a mitered, a squarely cut, and a circular E-plane bend in rectangular waveguide is implemented by combining the port reflection coefficient method and the mode-matching method. Based on the port reflection coefficient method, the two-port waveguide bend is converted to a one-port structure comprised of cascaded waveguide step-junctions. After solving the reflection coefficient caused by these waveguide step-junctions using the mode-matching method, the desired scattering parameters of the bend are obtained readily. Convergence properties of the calculated numerical results are validated. Influences of the mitered, the squarely cut, and the circular part of the bend on the scattering parameters are investigated, and the optimal design dimensions for realizing wide-band and low return loss bends are found. Based on the optimal compensation dimension, an E-plane waveguide circular bend is fabricated and tested. The measured result agrees well with the theoretical prediction, and a full-band matched bend is practically realized.

In this paper we propose a new far-field RCS prediction method using cylindrical or planar near-field RCS data. First we derive the relation between RCS and the scattering coefficient using physical optics technique. The far-field RCS prediction algorithm is obtained by approximating the relation using the condition of Fresnel region and the paraxial constraint of scanning angle in the case of cylindrical or planar scanning. Finally we predict the far-field RCS using measured or calculated near-field RCS data of the conducting rectangular prism or plate. The validity of the proposed algorithm is demonstrated.

The H-polarized diffraction by a wedge consisting of perfect conductor and lossless dielectric is investigated by employing the dual integral equations. Its physical optics diffraction coefficients are expressed in a finite series of cotangent functions weighted by the Fresnel reflection coefficients. A correction rule is extracted from the difference between the diffraction coefficients of the physical optics field and those of the exact solution to a perfectly conducting wedge. The angular period of the cotangent functions is changed to satisfy the edge condition at the tip of the wedge, and the poles of the cotangent functions are relocated to cancel out the incident field in the artificially complementary region. Numerical results assure that the presented correction is highly effective for reducing the error posed in the physical optics solution.

Investigated is a guided-wave device for dividing optical power into three equal parts. The device fundamentally consists of a three-waveguide tapered-velocity coupler which is designed to operate under the adiabatic condition. Field distributions of the local normal modes along the coupler explain basic principles of the device. Its performance is confirmed through numerical simulations by means of finite difference beam propagation method.

A method for analyzing the scattering of electromagnetic waves by a general bianisotropic slab is presented by extending the author's previous approaches for anisotropic, chiral, and those periodic media. The analysis is formulated in a unified matrix form, so that scattering characteristics can be obtained by system matrix calculations. The method can be extended straightforwardly to multilayerd and periodic structures. The scattering efficiencies are obtained for the incidence of not only linearly polarized waves but also circularly polarized waves.

Polarization transformation characteristics of a statified slab consisting of uniaxial chiral layers are investigated. It is assumed that a plane electromagnetic wave with arbitrary polarization is normally incident from free space on the stratified slab, which is located on a dielectric substrate. Note that the electric field inside a uniaxial chiral layer is expressed as a sum of four plane waves with different wavenumbers. The wavenumbers are found by seeking non-trivial solutions of the constitutive relations with Maxwell's equations. The electric field components of the transmitted and reflected waves can be obtained from a chainmatrix formalism. The powers and the Stokes parameters of the two waves are represented in terms of their electric field components. As is well known, the Stokes parameters uniquely describe every possible state of polarization of a plane wave. Numerical results are presented for two types of uniaxial chiral structure. The cross- and co-polarized powers and the Stokes parameters of the transmitted and reflected waves are computed for the incident plane wave of linear polarization. The results demonstrate a significant polarization transformation of the transmitted wave. Then it is shown that the stratified slab can be used as efficient polarization-transformation transmission filters active at some frequency band.

Gaussian beams constitute a very powerful tool to analyze radiation and scattering problems in high frequency regimes. The analysis of this kind of beams may be done by performing an analytical continuation of the real sources into the complex space. This is also a very powerful technique that arise, not only to this kind of solutions, but also to other solutions that may be very useful even for low frequency regimes. A complete parametrization of real propagation space in terms of the different type of complex beams solutions is presented in this paper. The analysis in the complex domain arises to different regions in the real space which may be anticipated and described through analytical transition regions. Some important conclusions may be derived from the results obtained, in particular the results related to the complex far field condition.

Scattering data from radar targets are analyzed in the time-frequency domain by using wavelet transform, and the scattering mechanisms are investigated. The wavelet transform used here is a powerful tool for the analysis of scattering data, because it can provide better insights into scattering mechanisms that are not immediately apparent in either the time or frequency domain. First, two types of wavelet transforms that are applied to the time domain data and to the frequency domain data are defined, and the multi-resolution characteristics of them are discussed. Next, the scattering data from a conducting cylinder, two parallel conducting cylinders, a parallel-plate waveguide cavity, and a rectangular cavity in the underground are analyzed by using these wavelet transforms to reveal the scattering mechanisms. In the resulting time-frequency displays, the scattering mechanisms including specular reflection, creeping wave, resonance, and dispersion are clearly observed and identified.

A bicomplex representation for time-harmonic electromagnetic fields appearing in scattering and diffraction problems is given using two imaginary units i and j. Fieldsolution integral-expressions obtained in the high-frequency and low-frequency limits are shown to provide the new relation between high-frequency diffraction and low-frequency scattering. Simple examples for direct scattering problems are illustrated. It may also be possible to characterize electric or magnetic currents induced on the obstacle in terms of geometrical optics far-fields. This paper outlines some algebraic rules of bicomplex mathematics for diffraction or scattering fields and describes mathematical evidence of the solutions. Major discussions on the relationship between high-frequency and low-frequency fields are relegated to the companion paper which will be published in another journal.

A rigorous radar cross section (RCS) analysis is carried out for two-dimensional rectangular and circular cavities with double-layer material loading by means of the Wiener-Hopf (WH) technique and the Riemann-Hilbert problem (RHP) technique, respectively. Both E and H polarizations are treated. The WH solution for the rectangular cavity and the RHP solution for the circular cavity involve numerical inversion of matrix equations. Since both methods take into account the edge condition explicitly, the convergence of the WH and RHP solutions is rapid and the final results are valid over a broad frequency range. Illustrative numerical examples on the monostatic and bistatic RCS are presented for various physical parameters and the far field scattering characteristics are discussed in detail. It is shown that the double-layer lossy meterial loading inside the cavities leads to the significant RCS reduction.

Equivalence of physical optics (PO) and aperture field integration method (AFIM) in the full 360 observation angle is discussed for polyhedron approximate reflectors; the necessary conditions of integration surface in AFIM for the equivalence to PO are presented. In addition to the condition that complete equivalent currents consisting of both geometrical optics (GO) reflected fields from the reflector and direct incident fields from the feed source are used, the integration surface should cap the reflector perfectly and should be in the illuminated region of the GO reflected field. Validity of the conditions is numerically confirmed for a two-dimensional (2-D) strip reflector, 3-D corner reflectors and a 2-D polyhedron approximate reflector.

In this paper an algorithm for numerical investigation of the transmission line having a generalized polygonal cross-section and open interface is proposed. Solution of the eigenmode problem is based on the method called the domain product technique, which employs a Mathieu function expansion and provides an efficient technique to the analysis of the structures with multiangular boundaries. An agreement at the obtained numerical results with existing data confirms the applicability of the theoretical analysis given in the paper.

In this paper, scattering problem of the directional coupler for the slab waveguides are analyzed by the mode-matching method in the sense of least squares for the lowest order even TE mode incidence. It is considered that the analysis of this coupler for the slab waveguides presents the fundamental data to design the directional coupler for the three dimensional waveguides. This directional coupler is composed of three parallel slabs which are placed at equal space in the dielectric medium. Respective slabs are core regions of three respective waveguides. The periodic groove structure of finite extent is formed on the both surfaces of core region of the central waveguide among them. The power of incident TE mode is coupled to other two waveguides through periodic groove structure. The coupled TE mode propagates in the other waveguides to the same or opposite direction for the direction of incident mode which propagates in the waveguide having periodic structure when the Bragg condition is selected appropriately. The scattered field of each region of this directional coupler is described by the superpositions of the plane waves with bandlimited spectra, respectively. These approximate wave functions are determined by the minimization of the mean-square boundary residual. This method results in the simultaneous Fredholm type integral equations of the second kind for these spectra. The first order approximate solutions of the integral equations are derived and the coupling efficiency and scattered fields are analyzed on the basis of those solutions in this paper.

Three-dimensional (3-D) instrumentation using an image sequence is a promising instrumentation method for intelligent systems in which accurate 3-D information is required. However, real-time instrumentation is difficult since much computation time and a large memory bandwidth are required. In this paper, a 3-D instrumentation VLSI processor with a concurrent memory-access scheme is proposed. To reduce the access time, frequently used data are stored in a cache register array and are concurrently transferred to processing elements using simple interconnections to the 8-nearest neighbor registers. Based on a row and column memory access pattern, we propose a diagonally interleaved frame memory by which pixel values of a row and column are stored across memory modules. Based on the concurrent memory-access scheme, a 40 GOPS vprocessor is designed and the delay time for the instrumentation is estimated to be 42 ms for a 256256 images.

A new optical wavelength demultiplexer using quasi-phase-matched sum-frequency-generation (QPM-SFG) is proposed. The device consists of an optical deflector using Pockels effect and a nonlinear crystal with a periodic structure. The demultiplexing characteristics of the device composed of a LiNbO₃ crystal are analyzed theoretically. Wavelength demultiplexing can be made simply by changes in the electric field applied to the deflector.