Mario Lucido

Scattering by Polygonal Cross-Section Dielectric Cylinders at Oblique Incidence

We analyze the scattering by polygonal cross-section lossless dielectric cylinders illuminated by an obliquely incident plane wave. The problem is formulated in terms of a system of surface integral equations opportunely devised so as to be valid for objects with edges and incident angles including the total reflection limit angle. By means of Galerkins method in the spectral domain with analytically Fourier-transformable expansion functions factorizing the correct edge behaviors and continuity conditions of the unknowns, convergence of exponential type is achieved and the coefficients of the scattering matrix are reduced to single integrals that can be efficiently evaluated. Numerical results for both near field and far field parameters are presented, showing the quick convergence of the method even when applied to composite cylindrical objects.

Analysis of the electromagnetic scattering by perfectly conducting convex polygonal cylinders

An effective method for the analysis of the scattering by a perfectly conducting convex polygonal cross-section cylinder is presented. The effectiveness stems from the generalization of the Neumann series, factorising the right edge behavior of the electromagnetic field, thus leading to a quickly convergent method. The induced currents, the radar cross section (RCS) and the induced field ratio have been evaluated.

Closed-Form Evaluation of the Second-Order Statistical Distribution of the Interferometric Phases in Dual-Baseline SAR Systems

Multichannel inteferometric synthetic aperture radar (InSAR) systems allow to improve the accuracy of the estimation of the height profiles of the observed scenes. Multichannel images can be acquired by using different sensors operating at different frequencies (multifrequency InSAR) or acquiring multiple images with slightly different view angles (multibaseline InSAR). The enhanced accuracy height estimation is obtained exploiting the multichannel interferometric phases and an a priori inaccurate ground profile and requires the knowledge of the joint probability distribution of the multichannel interferometric phases, whose evaluation in a closed form is very complicated and is not found in literature. In this paper, we evaluate the analytical form of the second-order probability density function (pdf) of dual-baseline InSAR phase interferograms, obtained from three mutually correlated interferometric images. The evaluation exploits the Gaussian model for the complex SAR images, takes into account the mutual correlation of all the images, and does not use any approximation. The closed form of the second-order joint pdf can be usefully adopted in statistical digital elevation model (DEM) estimation methods using dual-baseline SAR systems, which commonly use an approximate expression of the joint pdf of measured interferometric phases, given by the product of the marginal pdfs of each phase interferogram, obtained in the assumption of independent interferograms. The effect of this approximation is evaluated by computing the Cramer-Rao lower bounds and the mean square estimation errors obtained using the exact and the approximate model. Presented results represent the basis for the generalization to the case of more than two interferograms.

Electromagnetic Scattering by Multiple Perfectly Conducting Arbitrary Polygonal Cylinders

We analyze the scattering by multiple perfectly conducting cylinders with arbitrary polygonal cross-section. The proposed method is very efficient as few expansion functions are needed in a Galerkin scheme. This is achieved by means of the analytical regularization of the problem obtained by factorizing the correct edge singularity of the electromagnetic field. A particular attention has also been paid to the numerical computation of the integrals involved, and formulas for their accurate and quick evaluation are given.

A New High-Efficient Spectral-Domain Analysis of Single and Multiple Coupled Microstrip Lines in Planarly Layered Media

The analysis of propagation of bound and leaky modes in single and multiple coupled microstrip lines in planarly layered media by means of Galerkins method applied to an electric field integral-equation formulation in the spectral domain with Chebyshev polynomials basis functions weighted with the edge behavior of the unknown surface current densities on the metallic strips leads to the evaluation of improper integrals of oscillating functions with a slow asymptotic decay. In this paper, a new analytical technique for drastically speeding up the computation of such integrals is presented. First, suitable half-space contributions are pulled out of the kernels, which makes the integrands exponentially decaying functions. The integrals of the extracted contributions are then expressed as combinations of proper integrals and fast converging improper integrals by means of appropriate integration procedures in the complex plane.

Guaranteed-Convergence Method of Analysis of the Scattering by an Arbitrarily Oriented Zero-Thickness PEC Disk Buried in a Lossy Half-Space

In this paper, a guaranteed-convergence method for the accurate and efficient analysis of the electromagnetic scattering by an arbitrarily oriented zero-thickness perfectly electrically conducting (PEC) disk buried in a lossy half-space is presented. An electric field integral equation (EFIE) in the vector Hankel transform domain is obtained by expanding the unknown surface current density in cylindrical harmonics. A convergence of exponential type is achieved by means of Galerkins method with expansion functions reconstructing the expected physical behavior of the nth harmonic at the center and the edge of the disk. The obtained coefficient matrix can be quickly computed since its elements can be reviewed as the sum of single integrals efficiently evaluable by means of an analytical acceleration technique and double integrals of exponentially decaying functions.

Spectral Domain Analysis of Open Single and Coupled Microstrip Lines With Polygonal Cross-Section in Bound and Leaky Regimes

Aim of this work is the analysis of the propagation of bound and leaky modes in perfectly conducting open single and coupled microstrip lines with polygonal cross-section. The problem is formulated as a new numerically stable one-dimensional electric field integral equation (EFIE) in the spectral domain. Quick convergence is achieved by expanding the unknown surface current density with functions reconstructing the edge behaviour and continuity conditions in a Galerkin scheme. Due to the reciprocity, the impedance matrix has symmetries allowing to cut down the number of coefficients to be numerically evaluated. The choice of analytically Fourier transformable expansion functions leads to reduce the coefficients of the impedance matrix to single integrals efficiently evaluated by means of an analytical acceleration technique.

TM Scattering by Perfectly Conducting Polygonal Cross-Section Cylinders: A New Surface Current Density Expansion Retaining up to the Second-Order Edge Behavior

In the analysis of scattering by perfectly conducting cylinders with polygonal cross-section by means of surface integral operator formulations, fast convergence can be achieved by expanding the surface current density on each side with basis functions factorizing the correct behavior of the fields on the wedges. Usually, the factorized edge behavior is chosen to be coincident with the first order behavior prescribed by Meixners theory. However, it could not be the correct one and, consequently, the convergence of the method becomes increasingly slow as the theoretical behavior differs from the real one. This phenomenon is particularly notable when one or more of the predicted singularities unexpectedly disappear. To overcome this problem, in this work the analysis of TM scattering is made by introducing a new expansion devised so that only the first two terms are responsible for the reconstruction of the singularities while the remaining part of the expansion factorizes the second order edge behavior. Actually, the proposed expansion outperforms the one introduced by the authors in a previous work factorizing the first order edge behavior even when this is the correct one.

TE Scattering by Arbitrarily Connected Conducting Strips

The scattering by an arbitrary collection of perfectly conducting connected strips is analyzed for TE incidence. The studied configurations include both closed and open polygonal cross-section cylinders, as well as more complicated structures in which more than two strips are connected at a point. The proposed method is very efficient as few expansion functions are needed in a Galerkin scheme. This is achieved by means of expansion functions factorizing the correct edge singularity of the electromagnetic field, and ensuring the continuity of the current at connecting points.

A New High Efficient Analysis of the Scattering by a Perfectly Conducting Rectangular Plate

The analysis of the scattering by a perfectly conducting rectangular plate by means of Galerkins method in the spectral domain with products of Chebyshev polynomials of first and second kind multiplied by their orthogonal weights as basis functions is fast convergent even for scatterers size of some wavelengths but leads to the numerical evaluation of infinite double integrals of oscillating and slowly decaying functions. The aim of this paper is the introduction of a new analytical technique that allows to write such integrals as combinations of very quickly converging integrals.