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The containment of unwanted electromagnetic radiation and interference is a relevant topic for the system design of any electrical system, and even more for data centers. In this context, the racks hosting piles of servers are one of the main sources of electromagnetic noise. Such unwanted radiation can couple and interact with other computing machines, but also with sensitive electronic devices needed for the management and/or maintenance of the center. The aim of this work is to show how the proper stack-up of the trays in the rack gives rise to a decrease in the unwanted physical electromagnetic radiation. Based on the application of the spherical wave expansion technique, a multi-objective genetic algorithm is developed to evaluate the optimal set of rack configurations that allows for a reduction of the external radiated field. The algorithm and the implemented constraints are described, and the results are discussed.

This paper carries on a systematic analysis of the behavior of the time reversal (TR) voltage and current transfer functions used to locate faults and defects along lines in function of their terminal conditions expressed in terms of reflection coefficients. Transfer functions for solid and soft transversal faults and longitudinal defects are considered, covering all the possible scenarios. The reflection coefficients swing from values very close to 1 (open-end condition) up to values close to −1 (short-circuit condition) passing through values near zero (matching condition). The results are discussed to assess the accuracy and scalability of the electromagnetic TR method for unmatched media.

In this paper, the analysis of the accuracy of the electromagnetic time reversal method for unmatched media is carried out when the terminal impedances of the transmission line and/or of the defects along it are frequency dependent. Some numerical examples involving a medium-voltage power line and a high-speed interconnect are considered and the results discussed.

This paper applies the electromagnetic time reversal method to the identification of the location and to the quantification of the impedance Zd of longitudinal defects along transmission lines. A closed-form expression for the time-reversal current transfer function is derived. This new transfer function benefits from the same properties of that for solid or soft transversal faults, and hence, can be used for locating the defects along the line. Different scenarios are considered ranging from power lines to signals channels for high-speed digital systems at printed circuit board and package level. The results are discussed and used to assess the accuracy and scalability of the proposed method.

This contribution deals with the optimal placement of the decoupling capacitances on the gridded power delivery network of a multichip assembly with interposer. The optimization is performed by means of a nature-inspired algorithm of the genetic class. Different placement strategies are considered and compared. The cost function is based on the evaluation of the input impedance looked into the power and ground rails of the power distribution network and its comparison with a user-defined mask.

This paper analytically demonstrates that the boun-ded phase property of the voltage transfer function developed by Codino for the electromagnetic time-reversal method in unmatched media is also valid for the time-reversal current transfer function used as an estimator of the location along the line of soft defects with defect impedance different from zero. Few examples are proposed ranging from medium-voltage power lines to high-speed interconnects, which demonstrate the accuracy and scalability of the method.

The de-embedding of measurement fixtures is relevant for an accurate experimental characterization of radio frequency and digital electronic devices. The standard technique consists in removing the effects of the measurement fixtures by the calculation of the transfer scattering parameters (T-parameters) from the available measured (or simulated) global scattering parameters (S-parameters). The standard de-embedding is achieved by a multiple steps process, involving the S-to-T and subsequent T-to-S parameter conversion. In a typical measurement setup, two fixtures are usually placed before and after the device under test (DUT) allowing the connection of the device to the calibrated vector network analyzer coaxial ports. An alternative method is proposed in this paper: it is based on the newly developed multi-network cascading algorithm. The matrices involved in the fixture-DUT-fixture cascading gives rise to a non-linear set of equations that is in one step analytically solved in closed form, obtaining a unique solution. The method is shown to be effective and at least as accurate as the standard multi-step de-embedding one.

An accurate monitoring of power system behavior is a hot-topic for modern grid operation. Low-frequency oscillations (LFO), such as inter-area electromechanical oscillations, are detrimental phenomena impairing the development of the grid itself and also the integration of renewable sources. An interesting countermeasure to prevent the occurrence of such oscillations is to continuously identify their characteristic electromechanical mode parameters, possibly realizing an online monitoring system. In this paper an attempt to develop an online modal parameters identification system is done using machine learning techniques. An approach based on the development of a proper artificial neural network exploiting the frequency measurements coming from actual PMU devices is presented. The specifically developed offline training stage is fully detailed. The output results from the dynamic mode decomposition method are considered as reference in order to validate the machine learning approach. Some results are presented in order to validate the effectiveness of the proposed approach on data coming from recordings of real grid events. The main key points affecting the performance of the proposed technique are discussed by means of proper validation scenarios. This contribution is the first step of a more extended project whose final aim is the development of an artificial neural networks (ANN) architecture able to predict the system behavior (in a given time span) in terms of LFO modal parameters, and to classify the contingencies/disturbances based on an online training that has memory of the passed training samples.

An iterative optimization for decoupling capacitor placement on a power delivery network (PDN) is presented based on Genetic Algorithm (GA) and Artificial Neural Network (ANN). The ANN is first trained by an appropriate set of results obtained by a commercial simulator. Once the ANN is ready, it is used within an iterative GA process to place a minimum number of decoupling capacitors for minimizing the differences between the input impedance at one or more location, and the required target impedance. The combined GA&ndash, ANN process is shown to effectively provide results consistent with those obtained by a longer optimization based on commercial simulators. With the new approach the accuracy of the results remains at the same level, but the computational time is reduced by at least 30 times. Two test cases have been considered for validating the proposed approach, with the second one also being compared by experimental measurements.

The objective of this study is the development of an efficient methodology, based on the spherical wave expansion theory, to evaluate the total unwanted electromagnetic radiation of multiple radiation sources starting from the knowledge of the radiation characteristic of every single source considered as isolated. The specific application domain deals with the estimation of the electromagnetic interference from stacked trays in server racks. After having computed the radiation of each isolated tray, by using the spherical expansion technique the proper expansion coefficients are calculated. They are combined in a set of new coefficients that are used to reconstruct the estimated total field from the server rack. This study discusses the proposed methodology step by step and offers practical considerations on its implementation when measured data are given as input. The adopted numerical examples show in a quantitative way, through different graphs and comparisons, the limits and the advantages of the technique. The proposed method has been shown to reliably predict the radiation from stacked trays with only a few dB of uncertainty. The examples are based on numerically computed data sets of electromagnetic emissions from trays and racks but the proposed procedure is valid also for measured data.

The aim of this contribution is to develop a procedure in order to identify and to model the intrinsic electric discontinuities in high-voltage overhead transmission lines to better design power line communications applications. The modeling is based on the results of a rigorous campaign of measurement carried out in collaboration with the Italian Transmission System Operator TERNA. The high-frequency model of the line also takes into account the conductors transpositions and other stray effects that can have an impact on the propagation of the high-frequency signals.

The present work develops a unitary finite difference time domain (FDTD) formulation to take into account the unavoidable coupling, of resistive nature, among the N ports of a general termination network at the ends of lossy and externally excited multiconductor transmission lines. It completes the contribution of a previous paper where a FDTD scheme has been developed for the same coupling but for lossless and only internally excited lines. The developed vector time-domain equations are validated comparing their results with those obtained by a commercial circuit solver tool.

The ever growing complexity of electronic circuits placed at the ends of multiconductor transmission line models requires also taking into account the electrical coupling among all ports of their equivalent termination networks. This work develops an explicit finite difference time-domain scheme that takes into account a lumped resistive coupling among the N ports of a general termination network. The developed vector time-domain equations are validated comparing the results with those obtained by a commercial tool.

Small form factors and high bandwidth are two imperatives nowadays for three-dimensional integrated circuits (3-D-ICs). These requirements can be achieved by the use of through silicon vias, by the reduction of their radius and, at the same time, of the pitch among them. Having a considerable number of devices in a limited space inevitably increases the probability of the creation of defects (short, open, void, etc.). The study of the nature, topology, and creation mechanism of defects is crucial for 3-D-IC design. This paper suggests a procedure able to determine the nature of a defect (open- or short-circuit) and to estimate its position, basing its approach on the study of the electrical parameters of the defected structure, avoiding the use of invasive method such as Lock-in Thermography. A daisy-chain structure is manufactured and open or short defects are intentionally placed along the channel. With and without defects, the equivalent capacitance and inductance are extracted from the S-Parameters, from measurement and three-dimensional electromagnetic simulations, and used to define and validate the proposed procedure.

This work studies the possible reduction of the direct near-field radiation from electromagnetic bandgap-based comm-on-mode filters on printed circuit boards by using lossy dielectric and magnetic materials. Different combinations of materials are considered and numerically simulated. The comparisons of their performances are reported and discussed.

Decoupling capacitors are fundamental keys for the reduction of transient noise in power delivery networks, their arrangement and values are crucial for reaching this goal. This work deals with the optimization of the decoupling capacitors of a power delivery network by using a nature-inspired algorithm. In particular, the capacitance value and the location of three decoupling capacitors are optimized in order to obtain an input impedance below a specific mask, by using a nature-inspired algorithm, the genetic one, in combination with two electromagnetic solvers used to compute the objective function. An experimental board is designed and manufactured, measurements are performed to validate the numerical results.

In this work preliminary yet comprehensive considerations are reported on the possibility for remote monitoring of degraded compression and bolted joints on high voltage overhead power lines. Measurements are performed on new, naturally aged, and artificially degraded joints to quantify the impedance discontinuity introduced along typical HV overhead lines. Numerical simulations, a preliminary time domain reflectometry (TDR) measurement campaign, and circuit simulations are performed on a real power line to study the TDR-based capabilities for the identification of the investigated joint impedances. This study sets the basic concepts to the development of a remote monitoring system for quantifying and locating degraded joints.

Common-mode (CM) noise on differential signals can be suppressed by planar electromagnetic bandgap (EBG) technologies. In this study, two new CM filter structures were designed, fabricated, and measured. The filters are based on a previously proposed geometry, a “sandwich-type” EBG structure that resonates at the desired filter frequency; however, the new filters are placed on the top of the PCB as a surface-mount component, instead of being implemented within the PCB stackup. Stripline and microstrip versions of the surface-mount filter are considered. The filters can be easily removed and substituted with another one that is designed to filter a different frequency but maintains the same footprint and external dimensions. In addition, the surface-mount filter allows us to incorporate dc blocking capacitors into the microstrip version of the filter, thus providing two functions in one package. The total radiated power (TRP) of the implemented filter is investigated and discussed. RF absorbing material and traditional shielding are considered to reduce the TRP.

This paper deals with the filters based on EBG cavities employed for reducing common-mode currents along differential stripline traces. The crosstalk among differential interconnects routed in close proximity to EBG-based filters, and next to filtered pairs, is accurately quantified. The comparison between the experimental and simulation frequency-domain results validate the proposed filter's effectiveness and make the simulation model reliable for investigating the complex multichannel crosstalk problem. This paper focuses on the stripline environment, where crosstalk occurs among traces routed on adjacent layers, with the EBG cavity acting as a coupling path. Multichannel time-domain simulations complete the characterization of the filter, showing the limited effects of the filter on the intentional differential signal, and the beneficial impact on reducing the potentially radiating common-mode harmonics. The quantification of the common-mode spectrum shows that the filtered harmonics are reduced by 10–15 dB; thus, minimizing the corresponding electromagnetic interference. Design guidelines are defined for the filter layout according to the relative position of unfiltered differential traces, when constraints force them to be placed in close proximity to EBG cavities and filtered pairs. In particular, the best layout for unfiltered traces on adjacent layers is orthogonal with respect to the filtered pair, whereas the parallel routing should be carefully used taking into account the signal bandwidth on the victim pairs.

To reduce the noise created by a power delivery network, the number, the value of decoupling capacitors and their arrangement on the board are critical to reaching this goal. This work deals with specific improvements, implemented on a genetic algorithm, which used for the optimization of the decoupling capacitors in order to obtain the frequency spectrum of the input impedance in different positions on the network, below previously defined values. Measurements are performed on a specifically manufactured board in order to validate the effectiveness of the proposed algorithm and the optimization results obtained for a specific example board.

This work presents the feasibility study of an on-line monitoring technique aimed to discover unwanted variations of longitudinal impedance along the line (also named &ldquo, impedance discontinuities&rdquo, ) and, possibly, incipient faults typically occurring on high voltage power transmission lines, like those generated by oxidated midspan joints or bolted joints usually present on such lines. In this paper, the focus is placed on the application and proper customization of a technique based on the time-domain reflectometry (TDR) technique when applied to an in-service high-voltage overhead line. An extensive set of numerical simulations are provided in order to highlight the critical points of this particular application scenario, especially those that concern the modeling of both the TDR signal injection strategy and the required high-voltage coupling devices, and to plan a measurement activity. The modeling and simulation approach followed for the study of either the overhead line or the on-line TDR system is fully detailed, discussing three main strategies. Furthermore, some measurement data that were used to characterize the specific coupling device selected for this application at high frequency&mdash, that is, a capacitive voltage transformer (CVT)&mdash, are presented and discussed too. This work sets the basic concepts underlying the implementation of an on-line remote monitoring system based on reflectometric principles for in-service lines, showing how much impact is introduced by the high-voltage coupling strategy on the amplitude of the detected reflected voltage waves (also named &ldquo, voltage echoes&rdquo, ).

The aim of this paper is to clarify some important aspects associated with the possibility to detect degraded compression and bolted joints in power transmission lines using a time-domain reflectometry (TDR)-based remote monitoring. The optimization of a TDR-based remote monitoring method is discussed, studying the effects of the source impedance, source-to-line connection, line characteristic impedance, and scope settings, providing useful guidelines for a future method and instrumentation refinement. The experimental results are presented consisting in the inclusion of lumped resistors of several values along a 130-kV power transmission line. The minimum detectable resistance is discussed based on the present available hardware. The TDR-based method is shown to be able to also identify the main features of the line layout such as phase transpositions and different heights of adjacent towers. This paper represents a preliminary base to keep developing the proposed method, with the aim to overcome the actual limitations (costs, reliability, etc.) in power line monitoring.

The concept of reliability and safety is the foundation of every kind of system used in the aeronautical and aerospace applications and diagnostics contributes significantly to this goal. In the literature there are several methods (thermal, on test bench, etc...) that perform diagnostics of electric motors both in the production phase and in the test phase in the sample. These methods tend to test the electrical and mechanical parameters. Using a frequency analysis technique SFRA (Sweep Frequency Response Analysis), it's possible to have a "signature" in frequency of the electric motor. The reference standard IEC 60076-18 (still in the process of study and development), which regulates the diagnosis through SFRA technique for power transformers, does not contain any guidelines on the interpretation of the results. Almost all of the existing researches are addressed on oil insulated transformers. The research aims to investigate the measurement methodologies for the characterization of the stators and for the faults detection caused by the manufacturing process.