Rodolfo Araneo

Fast MoM Analysis of the Shielding Effectiveness of Rectangular Enclosures With Apertures, Metal Plates, and Conducting Objects

The evaluation of the shielding effectiveness (SE) of rectangular metallic enclosures having apertures in their walls and loaded with conducting bodies is the subject of this paper. The conducting objects can be either modifications of the inner part of the enclosure (e.g., simple metal plates or protrusions of the walls) or elements to be protected from external fields (e.g., printed circuit boards or metallic boxes). The SE of such enclosures is thus investigated through an efficient integral formulation based on the method of moments. The proposed approach makes use of a very fast computation of the enclosure Greens functions, based on the Ewald representation and interpolation techniques. The analysis shows that the classical SE of enclosures (calculated when a uniform plane wave impinges on the aperture of an empty enclosure) can be a very tricky figure of merit since the field inside the shield can be seriously affected by the possible presence of 2-D or 3-D conducting loads, especially in the frequency range above the first resonant frequency of the aperture-enclosure system. Comparisons with full-wave results obtained through different commercial software confirm the validity of the proposed technique and its excellent performance.

Piezo‐Semiconductive Quasi‐1D Nanodevices with or without Anti‐Symmetry

The piezopotential in floating, homogeneous, quasi-1D piezo-semiconductive nanostructures under axial stress is an anti-symmetric (i.e., odd) function of force. Here, after introducing piezo-nano-devices with floating electrodes for maximum piezo-potential, we show that breaking the anti-symmetric nature of the piezopotential-force relation, for instance by using conical nanowires, can lead to better nanogenerators, piezotronic and piezophototronic devices.

EMC Issues in High-Power Grid-Connected Photovoltaic Plants

This paper outlines the main electromagnetic compatibility issues frequently encountered in high-power grid-connected photovoltaic (PV) systems, and proposes several guidelines that allow to obtain an effective and highly efficient layout of the plant. At first, with reference to a 1-MWp PV plant of Sorgenia Solar, Italy, the paper focuses on the peculiar aspects concerning the radio-frequency behavior of a large-size PV plant: the great extent of the direct-current cabling, the capacitance toward earth of the PV source, the common-mode (CM) disturbance generated by inverters, the galvanic isolation ensured by dedicated low-voltage power transformers, and the presence of resonant circuits for CM leakage currents. The dominant electromagnetic phenomena and coupling mechanisms are pointed out by means of an equivalent circuit and through measurements. In the light of the matured experience, several guidelines are proposed and a new reliable layout is implemented on a second 1-MWp PV plant. New measurements confirm the validity of the proposed design strategy.

An Efficient MoM Formulation for the Evaluation of the Shielding Effectiveness of Rectangular Enclosures With Thin and Thick Apertures

A detailed analysis of the effects of finite-thickness apertures on the shielding properties of a rectangular metallic box is carried out through an efficient full-wave code based on the method of moments in the spatial domain. An incident plane wave having arbitrary polarization and incidence angle is assumed as a field source. The evaluation of the cavity Green function is accelerated by an application of the Ewald sum technique with a novel Ewald splitting parameter valid for high frequencies, and a recently proposed integral-equation-based approximate model of the aperture thickness is also applied. Numerical results are validated by comparisons with those obtained by means of commercial codes based on different numerical approaches and show rigorously that the effects of a finite thickness can usually be neglected (at least, at sufficiently low frequencies), with the noticeable exception of long slots. The effects of common limiting assumptions adopted in the study of enclosures with zero-thickness apertures are also investigated.

Shielding Effectiveness of Periodic Screens Against Finite High-Impedance Near-Field Sources

The shielding effectiveness of artificial periodic screens is investigated with reference to high-frequency high-impedance near fields produced by arbitrarily oriented electric dipoles. The screens are formed by metallic objects of arbitrary shape displaced in a 2-D lattice. The problem is first studied through a full-wave approach, using the array scanning method in conjunction with a periodic method of moments in the spatial domain. Next, the shielding problem is solved analytically in some characteristic electromagnetic compatibility configurations through the use of approximate low-frequency homogeneous models together with a classical analysis in the spectral domain. Finally, the solutions are compared with those deriving from the use of the so-called transmission-line approximation. The provided results show the suitability of the analytical approaches in dealing with finite sources different from standard plane-wave excitations and give a useful tool for the design of periodic shields.

Extraction of broad-band passive lumped equivalent circuits of microwave discontinuities

A systematic general-purpose technique for the extraction of equivalent circuits of lumped discontinuities and interconnects from full-wave electromagnetic-field numerical data is presented. The main feature of the method consists of approximating the simulated data in order to generate a passive and feasible circuit in an automatic way. All the aspects of the methodology are addressed. Particular emphasis is laid on the approximation step, about which a new technique is proposed

Low-Frequency Dominant-Mode Propagation in Spatially Dispersive Graphene Nanowaveguides

Dispersion properties of the dominant modes supported by different 2-D graphene-based nanowaveguides are studied by means of an exact approach based on the transverse-resonance technique and using an equivalent-circuit representation of graphene sheets which also takes into account the spatially dispersive nature of the graphene conductivity: it is quantitatively shown that neglecting spatial-dispersion effects can cause errors in the determination of the modal properties of extremely slow surface waves, also well below the terahertz regime. The modal features of graphene nanowaveguides are thus investigated in detail showing their potential in future nanoelectromagnetic and nanophotonic applications.

Efficient Evaluation of the 3-D Periodic Green's Function Through the Ewald Method

The Ewald method is efficiently applied for the computation of the Greens function for a 3-D array of phased point sources. A best splitting parameter E, which avoids the loss of accuracy occurring at high frequencies while maintaining rapidly converging properties, is derived. The loss of significant digits in the calculation of the modified spatial and spectral series involved in the Ewald summation technique can be set by the user, thus limiting the total error in the computation to a controllable level. Particular care is also given to the best way of summing the series that appear in the Ewald method and a new efficient algorithm for the reduction of the involved three-index series to one-index series is proposed, which allows for a further acceleration of the computation. Numerical results are presented to show the validity and efficiency of the proposed formulation.

Alternative Definitions for the Time-Domain Shielding Effectiveness of Enclosures

The assessment of the shielding effectiveness of enclosures under transient conditions calls for an accurate analysis of fundamental aspects. Stemming from a correct understanding of the coupling mechanism and from a victim point of view, new shielding parameters are proposed as figures of merit to designate the actual effectiveness of an electromagnetic enclosure. Their suitability is tested in different configurations excited by typical transient electromagnetic threats.

Two-port equivalent of PCB discontinuities in the wavelet domain

A novel wavelet-based technique is presented for the extraction of two-port equivalents of common printed circuit board (PCB) discontinuities. The wavelet-transformed scattering parameters of the discontinuity can be included in a wavelet equivalent of TEM wave propagation paths along the PCB in order to obtain an overall equivalent of the whole structure under analysis. The wavelet representation minimizes the CPU time and computer storage requirements while maintaining excellent accuracy, thus, it proves to be a very useful modeling tool, especially in the design stage.