Fulvio Schettino

Improving Channel Capacity Using Adaptive MIMO Antennas

A novel type of multiple-input multiple-output (MIMO) antenna employing parasitic elements is presented. A proper model for the parasitic-MIMO system is first discussed and then numerically and experimentally investigated. The results show that the proposed solution can significantly improve the performance of the communication system with a minimum impact on the complexity and cost of the overall system

A simple and robust adaptive parasitic antenna

A novel Uda-Yagi adaptive antenna is numerically and experimentally investigated. The antenna consists of an active element and a relatively large number of parasitic elements closed on two different loads selectable by simple electronic switches. The use of fuzzy-logic based cost function and self-adaptive biological beamforming algorithms allows to obtain quite good performances both in terms of signal to interference plus noise ratio and voltage standing wave ratio. The antenna is simple, low cost, and is robust with respect to mechanical and electrical tolerances and with respect to failures of some passive elements. Experimental results on two different prototypes confirm the good performances of the proposed antenna.

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.

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.

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.

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.

An Investigation on UWB-MIMO Communication Systems Based on an Experimental Channel Characterization

The advantages of multiple-input multiple-output (MIMO) technology in ultrawideband (UWB) communication systems are investigated evaluating the channel capacity from measurements taken in indoor environments. The results suggest that in practical instances spatial diversity is more attractive than spatial multiplexing for ultrawideband systems.

The Degrees of Freedom of Wireless NetworksVia Cut-Set Integrals

The problem of determining the number of spatial degrees of freedom (d.o.f.) of the signals carrying information in a wireless network is reduced to the computation of the geometric variation of the environment with respect to the cut through which the information must flow. Physically, this has an appealing interpretation in terms of the diversity induced on the cut by the possible richness of the scattering environment. Mathematically, this variation is expressed as an integral along the cut, which we call cut-set integral, and whose scaling order is evaluated exactly in the case of planar networks embedded in arbitrary three-dimensional (3-D) environments. Presented results shed some new light on the problem of computing the capacity of wireless networks, showing a fundamental limitation imposed by the size of the cut through which the information must flow. In an attempt to remove what may appear as apparent inconsistencies with previous literature, we also discuss how our upper bounds relate to corresponding lower bounds obtained using the techniques of multihop, hierarchical cooperation, and interference alignment.

Scattering by a zero‐thickness PEC disk: A new analytically regularizing procedure based on Helmholtz decomposition and Galerkin method

The aim of this paper is the introduction of a new analytically regularizing procedure, based on Helmholtz decomposition and Galerkin method, successfully employed to analyze the electromagnetic scattering by zero-thickness perfectly electrically conducting circular disk. After expanding the fields in cylindrical harmonics, the problem is formulated as an electric field integral equation in the vector Hankel transform domain. Assuming as unknowns the surface curl-free and divergence-free contributions of the surface current density, a second-kind Fredholm infinite matrix-operator equation is obtained by means of Galerkin method with expansion functions reconstructing the expected physical behavior of the surface current density and with closed-form spectral domain counterparts, which form a complete set of orthogonal eigenfunctions of the most singular part of the integral operator. The coefficients of the scattering matrix are single improper integrals which can be quickly computed by means of analytical asymptotic acceleration technique. Comparisons with the literature have been provided in order to show the accuracy and efficiency of the presented technique.