Switching Parameters Characterization of Aged IGBTs by Thermo-Electrical Overstress

This paper presents an experimental study and reports the monitored changes in the switching parameters (quoted in datasheets) of Insulated Gate Bipolar Transistors (IGBTs) when subjected to accelerated ageing through thermo-electrical overstress. The study describes how the accelerated ageing strategy was implemented. Tested IGBTs were characterized before and after accelerated ageing. Details are presented of the IGBT switching parameters characterization setup and the employed Double Pulse technique. Furthermore, the corresponding monitored changes in the turn-off delay time, fall time, energy loss during fall time, turn-off rate of change of collector voltage, turnon delay time, rise time, energy loss during rise time, turn-on rate of change of collector current, reverse recovery time, peak reverse recovery current and energy loss during reverse recovery are presented and discussed

An Experimental Investigation of the use of Q-Factor to Determine the Shielding Effectiveness of Electrically Large Equipment Enclosures with Apertures

The current method of obtaining a Shielding Effectiveness (SE) measurement involves field measurements both inside and outside the enclosure to be tested. In this paper, a relationship between the Shielding Effectiveness and the Q-factor of the enclosure under test (EUT) is investigated. Measurements are made in an anechoic chamber to obtain the Q-factor using a method previously detailed and to assess the Shielding Effectiveness of the enclosure under test. A relationship between Q-factor and shielding effectiveness is shown, and possible uses of this relationship are discussed

Structured Mesh Generation : Open-source automatic nonuniform mesh generation for FDTD simulation

This article describes a cuboid structured mesh generator suitable for 3D numerical modelling using techniques such as finite-difference time-domain (FDTD) and transmission-line matrix (TLM). The mesh generator takes as its input an unstructured triangular surface mesh such as is available from many CAD systems, determines a suitable variable mesh discretisation and generates solid and surface meshes in a format suitable for import by the numerical solver. The mesher is implemented in the MATLAB language and is available as open source software

Statistical distributions of the re-radiated spectrum from two correlated non-linear devices in a reverberation chamber

The statistics of the re-radiated spectrum from two correlated non-linear devices are investigated in a reverberation chamber. The distribution of the mean-value normalized statistics is interpreted using a double-Weibull statistical model. Comparisons are made with the re-radiation spectrum of a single non-linear device showing the statistical distributions to be different. Furthermore, experiments indicate the spatial correlation between the two non-linear devices changes the statistical distributions. This work enhances the understanding about the statistical aspects of the re-radiated spectrum from complex digital equipment

Electrical Parameters Characterization of Aged IGBTs by Thermo-Electrical Overstress

During their lifetime, power semiconductor devices such as Insulated Gate Bipolar Transistors (IGBTs) can suffer from different failure mechanisms. This paper reports the monitored changes in the electrical parameters of tested IGBTs when subjected to accelerated ageing through thermo-electrical overstress. The changes are indicative that the device is at the onset of failure and hence can be utilized within prognostic techniques so as to determine the health state of the device. The study describes how the accelerated ageing strategy was implemented providing details of the implemented hardware and software. Tested IGBTs were characterized before, during and after accelerated ageing. Details of the IGBT characterization setup are provided. Furthermore, the corresponding monitored changes in the die-attach X-Ray imagery, gate threshold voltage, collector leakage current, transfer characteristics, transconductance, output characteristics and internal free-wheeling diode forward characteristics are presented and discusse

Reverberation Chamber Immunity Testing : A novel methodology to avoid accidental DUT damage

Abstract—This paper shows a novel method of measuring the immunity of electronic devices inside reverberation chambers. Rather than using mode stirring or mode tuning with a constant power input into the chamber, we will present a method based on variable power that protects the DUT against accidental damage and also gives more information about the hardness of the DUT than the traditional methods

Virtual sensing directional hub MAC (VSDH-MAC) protocol with power control

Medium access control (MAC) protocols play a vital role in making effective use of a multiple access channel as it governs the achievable performance such as channel utilization and corresponding quality of service of wireless sensor networks (WSNs). In this paper, a virtual carrier sensing directional hub (VSDH) MAC protocol incorporating realistic directional antenna patterns is proposed for directional single hub centralized WSNs. While in most instances, MAC protocols assume idealized directional antenna patterns, the proposed VSDH-MAC protocol incorporates realistic directional antenna patterns to deliver enhanced link performance. We demonstrate that the use of directional antennas with a suitable MAC protocol can provide enhanced communication range and increased throughput with reduced energy consumption at each node, compared to the case when only omnidirectional antennas are used. For the scenarios considered in this study, results show that the average transmit power of the sensor nodes can be reduced by a factor of two, and at the same time offer significantly extended lifetime

Virtual HIRF tests in CST STUDIO SUITE™ : A Reverberant environment application

The prediction of the shielding performances of reverberant environments such as vehicle bodiesand metallic enclosure racks is an important part of the global design process of an electromagnetic system in order to ensure predefined performance specifications and fulfill the EMC standards. The desire for a reduced time-to-market means that there is often no time or budget for performing extensive prototyping and test measurements. These limitations make the reliable computation and prediction of the shielding properties of a given structure critical. To speed-up this time-consuming process numerical electromagnetic methods can be successfully adopted to analyze and characterize the system under test in terms of shielding performance. The data analysis and validation of results can be challenging due to rapid variation of data over a small frequency range and due to the high sensitivity to small geometric variations in such a strongly resonant environment. In this paper the studied test case consists of a metal enclosure, which is illuminated externally, and the internal response observed for different configurations of the internal structure including: coupling to straight and curved single wire lines; coupling through different types of aperture and material in the box walls and loading of the cavity by lossy materials to vary the Q-factor. The results are all presented as a reception aperture, a figure described by the ratio between the power received at a probe antenna and the power density of incident field. CST STUDIO SUITE™ was used to analyze the electromagnetic behavior of the aforementioned configurations. The different geometries have been constructed inside the frontend thanks to its powerful CAD capabilities. A plane wave has been used as excitation and receiving probes connected to a matched load (discrete ports) have been defined in order to calculate the reception aperture as a post processing step. Two different numerical EM methods have been applied to the case-study in order to cross-check the accuracy of the simulated results in the frequency range 1 - 6 GHz: 1) CST MICROWAVE STUDIO® Transient solver based on the Finite Integration technique (FIT). 2) CST MICROWAVE STUDIO® Frequency Domain solver based on the Finite Element method (FEM). The computed results showed a good agreement with the measured curves over the whole frequency range for all the examined configurations

Evaluation of the diffusion equation for modeling reverberant electromagnetic fields

Determination of the distribution of electromagnetic energy inside electrically large enclosed spaces is important in many electromagnetic compatibility applications, such as certification of aircraft and equipment shielding enclosures. The field inside such enclosed environments contains a dominant diffuse component due to multiple randomizing reflections from the enclosing surfaces. The power balance technique has been widely applied to the analysis of such problems; however, it is unable to account for the inhomogeneities in the field that arise when the absorption in the walls and contents of the enclosure is significant. In this paper we show how a diffusion equation approach can be applied to modeling diffuse electromagnetic fields and evaluate its potential for use in electromagnetic compatibility applications. Two canonical examples were investigated: A loaded cavity and two cavities coupled by a large aperture. The predictions of the diffusion model were compared to measurement data and found to be in good agreement. The diffusion model has a very low computational cost compared to other applicable techniques, such as full-wave simulation and ray-tracing, offering the potential for a radical increase in the efficiency of the solution high frequency electromagnetic shielding problems with complex topologies

Circuit and Electromagnetic Modelling of a low cost IEMI Sensor

The design of a low cost broadband Intentional Electromagnetic Interference (IEMI) detector and antenna to achieve a flat frequency response over a broad range is considered. SPICE simulation of the antenna, detector and low power log-amplifier circuit is used to predict the detector performance. The SPICE Antenna model is derived from numerical electromagnetic simulation. Simulations are compared with measured performance