Anna Pia Pastore

FDTD analysis of plane wave superposition to simulate susceptibility tests in reverberation chambers

The behavior of a device in a reverberation chamber can be analyzed as the same device irradiated by random plane waves. This work proposes an application of the finite difference time domain method to analyze the device by using a superposition of random plane waves, simulating the behavior of a reverberation chamber. The analysis of a transmission line compared with theoretical and experimental results in a reverberation chamber is reported

Field Penetration Through a Wire Mesh Screen Excited by a Reverberation Chamber Field: FDTD Analysis and Experiments

Field penetration into a metallic enclosure with a large aperture protected by a wire mesh screen is analyzed in this paper, using an in-house finite-difference time-domain code with a thin-wire approximation that accurately accounts for the cross between wires of the mesh. All results are experimentally validated using a reverberation chamber. Different enclosure dimensions and mesh sizes are considered, highlighting their implication on shielding performances.

Numerical and experimental analysis of the field to enclosure coupling in reverberation chamber and comparison with anechoic chamber

This paper presents a study of coupling between an external field and a metallic enclosure with a long aperture in the frequency range which includes several box resonances. A reverberation chamber (RC) and an anechoic chamber (AC) are considered as a field generation structure. In both cases, a customized FDTD code is used to calculate the current induced by the external field in a loop placed inside the enclosure. In order to simulate the AC facility, a single plane wave is used to represent the test field, whereas for the RC, the field is represented by a proper superposition of random plane waves. Numerical results are experimentally validated. The proposed method is useful to investigate the performance of the enclosure during its early design stage before the realization of a prototype

A Metrology Application of Reverberation Chambers: The Current Probe Calibration

This paper presents how it is possible to characterize a current probe in terms of its transfer impedance inside a reverberation chamber. The probe catches a floating wire placed inside the working volume of the chamber. The current on the wire is calculated from the knowledge of the total measured average field along the wire in the working volume. The current is calculated by representing the field in terms of a summation of random plane waves, where a finite-difference time-domain (FDTD) code is used to compute the current induced by each plane wave along the wire caught by the probe under test. Results for the current distribution along the wire are reported for several frequencies. Finally, the transfer impedance of commercial probes is recovered from the knowledge of the current and compared to the values given by the manufacturers and by an external laboratory

Innovative Systems for Cultural Heritage Conservation. Millimeter Wave Application for Non-invasive Monitoring and Treatment of Works of Art

Abstract A novel non invasive technique and a suitable apparatus for disinfestation of artworks is introduced. Non destructive and non invasive techniques are often irreplaceable in order to preserve and restore cultural heritage objects in its structure and shape. Although many techniques are available for art and archaeological works the non invasive methods are preferred as they leave the object untouched after treatment. Environmental parameters, such as humidity, can damage culture heritage objects and also results in spring up variety of pests and other micro-organisms. Non-invasive monitoring of these damage and also disinfestation treatments and drying with help of electromagnetic waves are preferred as they keep the object untouched after treatment. Application of millimeter waves for solving this problem is discussed here. Millimeter waves have high spatial resolution and absorption in water as well as in bio-objects that are usually moist and at the same time minimal interaction with dry culture heritage objects by itself. Different phases of the microwaves treatment (MW) of artworks are described, some results are shown and discussed. Many biological forms don’t survive over a certain temperature, called lethal temperature which, for most xylophages is about 53–55 °C, while for moulds and funguses is between 65 and 70 °C. In order to evaluate the management of disinfestation of works of art, incident power, temperature, exposure time were monitored. The monitoring of temperature is essential in order to prevent damages. A computer simulation allows to predict and monitor the heating process.

Modeling of the Reverberation Chamber Method for Determining the Shielding Properties of a Coaxial Cable

The paper considers the reverberation chamber (RC) method for the measurement of the shielding effectiveness (SE) of coaxial cables with braided shields. In particular, the voltage at the cable termination is numerically computed and compared to that measured in an RC. The RC field is represented by a finite summation of random plane waves, and a finite-difference time-domain (FDTD) code is used to calculate the outer shield current induced by the RC field. The knowledge of the shield current distribution allows the determination of the voltage at the cable terminations internal circuit after a proper numerical averaging. It is then compared to the measured voltage averaged over stirrer rotations. The method is applied to a commercially available cable model RG58, and using the nominal value for the transfer impedance of this cable type gives results in a satisfactory agreement with the measurements. Finally, the possibility of recovering the transfer impedance from the measured SE of the RC is discussed.

An innovative microwave system for wooden art object disinfestation

Purpose – Many objects made up of wood, as well as paper and carpets with artistic or cultural value, are seriously damaged by various infesting microorganisms and often such damage is irreversible. The purpose of this paper is to describe an equipment which has been realized, able to induce, inside the object to be treated, having any shape, and in particular in the infesting agents, a uniform distribution of temperature.Design/methodology/approach – The equipment consists of a metallic shielding chamber where the objects to be disinfested are placed. Here, through appropriate openings in the walls, electromagnetic energy at the frequency of the microwaves is introduced. The electromagnetic waves provoke a heating effect in the infesting biological forms with no significant thermal effects in the materials of the artistic object due to the different dielectric characteristics and to the very little percentages of water in them.Findings – The uniform distribution of temperature guarantees that the organis...

A Realistic Model for the Analysis of Heart Magnetic Stimulation

The aim of the paper is the development of an accurate numerical model to compute the current density flowing through the heart of a virtual human body, and induced by an external electric or magnetic excitation. The model has been experimentally validated and then applied to investigate the main characteristics of the heart magnetic stimulation. This has been carried out by comparing the current density induced in the cardiac region by an external magnetic pulse with the corresponding quantity due to the more traditional electric source. Magnetic stimulation is studied because it offers some advantages: in fact, compared with the electrical stimulation, this technique is contactless and might allow the stimulation of a dressed patient. The design constraint of the whole system is represented by the current density, whose waveform and intensity are a compromise between the strength of the magnetic induction field and the pulse rise time.

SAR numerical analysis of the whole human body exposed to a random field

This paper concerns numerical computation of the specific absorption rate (SAR) of a human body exposed to a random field. The model has been taken from the “Visible Human Body Project”. It is placed in a reverberation chamber (RC) whose internal field is simulated using the plane wave integral representation and which is numerically solved by a superposition of N plane waves repeated M times. This method is largely used for the electromagnetic compatibility (EMC) measurements and is also applied to calculate the absorbed power, and subsequently, temperature distribution of an object heated in an RC. In the present paper it is used to calculate the SAR at various frequencies for the whole human body and for some tissues, thereby recreating an environment which has characteristics very similar to the real environment that bombards us with dangerous radiations coming from different directions, and the field may assume random characteristics.

FDTD analysis of the field penetration through lossy materials in a reverberation chamber

This paper presents an electromagnetic analysis of lossy materials with a reverberation chamber (RC) and a case inside it. The geometrical structure is modeled with a multistructural FDTD technique. The domain of the RC is simulated with the classical Hill’s plane wave representation, the material domain is followed by an array of monodimensional FDTD and the case domain is made with the perfect electric conductor (PEC). Physically, the material is placed above an electrically large aperture of the case, that couples considered environments. Thanks to the high conductivity of the material, it is possible to separate numerical domains: only the material lattice is subordinate to the cell contraction. Numerical results are validated with the Fresnel theory and compared with experimental measurements.