Alvise Maschio

Dual-PEEC Modeling of a Two-Port TEM Cell for VHF Applications

Two-port TEM cells with rectangular cross section are commonly used to produce plane electromagnetic waves with high electric field. The non-uniform structure makes the use of numerical methods extremely useful in the design phase in order to achieve a very good behavior of the TEM cell over a wide frequency range of operation. In this paper an extended version of PEEC is used to study a real device and results are compared with experimental ones.

Coaxial Waveguide Methods for Shielding Effectiveness Measurement of Planar Materials Up to 18 GHz

The issue concerning the measurement of the shielding effectiveness (SE) of planar materials over a wide frequency range is of crucial relevance in several electromagnetic compatibility applications. This paper describes three different coaxial specimen holders for the measurement of the SE of thin metallic films over a nonconducting substrate or sandwiched between two insulating layers from a few kHz up to 18 GHz. Besides the well-known ASTM D4935 flanged coaxial cell, two novel versions of coaxial fixtures with an interrupted and continuous inner conductor are presented and compared. Their limits of applicability, advantages, and drawbacks are discussed with respect to frequency, sample characteristics, and test procedure. The analysis is performed by the use of simple equivalent circuit models, experimentally validated measuring thin copper films of different thicknesses which are deposited on kapton substrates by magnetron sputtering. It is demonstrated that the use of the three methods, properly combined, provides reliable SE results in the overall considered frequency range. It is also shown that the measurement of conducting films between two dielectric layers is critical at frequencies lower than some tens of MHz.

Characterization of nanostructured copper films for electromagnetic shield

Purpose – The purpose of this paper is to obtain a multidisciplinary characterization of nanostructured copper films for electromagnetic shields.Design/methodology/approach – Structural and electrical analysis have been applied, on copper nanometric films produced by a magnetron sputtering device.Findings – Data are provided for copper films realized by magnetron sputtering deposition on glass, in different operating conditions.Practical implications – A multidisciplinary comprehension of shielding effectiveness of nanostructured thin films can be important in many applications where there are electromagnetic compatibility problems.Originality/value – The paper gives a valuable set of information for the characterization of nanometric copper thin films.

Identification of an equivalent model for the permanent magnets of a magnetron sputtering device

Purpose – The aim of the work was to obtain an auxiliary instrument able to give the magnetic configuration of a magnetron sputtering device for operation with targets, magnetic and non magnetic, with different heights, starting from a device with no detailed information of the source.Design/methodology/approach – An inverse problem has been dealt with. A 2D numerical analysis has been performed, which utilizes as a starting point a model identified with a simple analytical procedure based on measurements.Findings – A satisfactory equivalent model has been identified, and validated in several different conditions.Originality/value – The proposed approach can be applied when no detailed information of the source is available, in the case of a cathode without a ferromagnetic yoke.

Shielding effectiveness of construction materials

Shielding effectiveness measurement, up to the GHz range, of construction materials with different compositions is an important issue. In this paper a coaxial waveguide, originally developed for thin films, is proposed as a simple device able to perform measurements on test samples with a thickness of a few millimetres. A calibration of the test system, with length extended of 5 mm, has been done both with a theoretical evaluation and an experimental measurement. Data obtained with construction materials of current interest for research are presented. With respect to similar systems reported in literature, where data up to 1.5 GHz are shown, this system has proven to be appropriate for measurements up to 3 GHz without too stringent tolerances in the sample geometry and without contact problems. Moreover, with inorganic polymers test samples, a clear relation between shielding effectiveness and heating temperature of the material has been observed.

Human exposure to pulsed current waveforms below 100 kHz

A tool for the analysis below 100 kHz of pulsed current waveforms with reference to human exposure has been developed. It consists of a dedicated program written in Matlab. As input data, a trapezoidal pulsed current waveform has been considered, and, varying the rise time and the duty-cycle, a parametric analysis has been performed. Also a noise superimposed to the signal has been considered. Parameters relevant to human exposure have been calculated following the ICNIRP Guidelines. A schematic operative diagram for metal inert gas welding applications is proposed; an experimental set-up has been built and the obtained results are reported.

Aluminium nitride films on glass

Purpose of this work is to realize AlN films with preferred crystal orientation on a magnetron sputtering system at different pressure values, in particular towards low-pressure gas discharge operative range, where few data are available in literature. In this respect, explored operative pressures have been 0.07 and 0.12 Pa, together with the more common values of 0.3 and 0.7 Pa. Reactive Ar-N2 mixtures (50%-50% and 0%-100%) and a DC-pulsed power supply have been used, and films have been deposited on glass substrate. Films thicknesses have been measured with surface profiler, and XRD analyses have been performed. Experimental data are presented; the best results with respect to adhesion, deposition rate and film crystallinity with the same deposition time have been obtained with mixtures 50% Ar - 50% N2 at 0.12 and 0.3 Pa.

Development of an improved version of sample holder for measuring the shielding effectiveness of planar films

An improved version of a coaxial sample holder with continuous inner conductor for measuring the shielding ef- fectiveness of planar films is presented. Keeping the design idea of the previously realized version of inner conductor split in two parts that are screwed on the sample under test, new aspects are: presence of tapered transitions, compact realization, and overall small size (total length less than 150 mm; maximum diameter of the cylindrical device of 48 mm). The theoretical only TEM mode maximum frequency is about 5 GHz. The assembly of the device is easy, as it is the sample preparation. Experi- mental data have been get in the range 0.1 MHz-3 GHz by using a vector network analyzer. The reliability of the system has been proved by using, as reference samples, copper and aluminium thin films deposited by DC magnetron sputtering on kapton substrates. Films with different thicknesses have been prepared, with values around a few hundreds of nanometers, as measured by using a surface profiler. The shielding effectiveness experimental data of the used reference samples are reported and are well in agreement with the theoretical values.

PEEC modeling of a two-port TEM cell for radio frequency applications

Two-port TEM cells with rectangular cross-section are commonly used to produce plane electromagnetic waves with high electric field. The non-uniformity of the system makes the use of numerical methods extremely useful in the design phase in order to achieve a very good behavior of the TEM cell over a wide frequency range of operation. In this paper an extended version of PEEC is used to study a real device and results are compared with experimental ones.

Magnetic shielding of MV/LV substations: Numerical modeling and experimental validation

A three-dimensional integral procedure based on the cell method and suitable for simulating non-magnetic shields has been proposed recently. Its validation against systematic measurements is here presented. A good agreement between computed and measured magnetic field RMS values confirms that the proposed integral procedure can be used confidently in designing shielding apparatuses for MV/LV substations.