Impulsion électromagnétique

Résumé

vignette|redresse=1.2|Simulateur d'EMP HAGII-C testé sur un avion Boeing E-4 (1979). Une impulsion électromagnétique (IEM), également connue sous le nom EMP (de l'anglais electromagnetic pulse) est une émission d'ondes électromagnétiques brève et de très forte amplitude qui peut détruire de nombreux appareils électriques et électroniques (reliés au courant et non protégés) et brouiller les télécommunications. Cette impulsion peut être générée artificiellement par une explosion nucléaire ou un générateur à micro-ondes, mais peut aussi être d'origine naturelle, comme la foudre, une éruption solaire ou l'électricité statique. Les applications d'une IEM peuvent être militaires, mais aussi industrielles ou médicales. Types d'impulsions électromagnétiques Foudre vignette|Un orage à Sydney en Australie, en 1991 : un éclair toutes les 30 secondes pendant deux heures. Foudre La foudre est la plus connue des IEM, c'est un phénomène naturel de décharge électrostatique,

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Inflight Microwave Drying Process of Micro-droplets for High Resolution 3D printing

Kwanghoon Choi

A new Additive-Manufacturing (AM) or 3D printing concept is proposed to improve the printing resolution for metal additive manufacturing in the frame of the SFA-AM project, Powder Focusing for Beam-Induced Laser 3D Printing. The project aims to transport small powder particles (largest diameter < 10 um) at a high throughput to a spot smaller than 20 µm. To realize the objective, a metal ion included liquid is suggested as a source medium similar to the inkjet process, and the droplet is employed as a container for the metal ion transport. The key challenges of achieving this goal are 1) droplet size control and 2) efficient microwave heating that can dry the liquid portion of the dynamic droplet at a high-speed (3 m/s). The most demanding part is the development of a miniaturized, very concentrated field density microwave resonator where the droplet is passing through. This follows from the extremely short interaction time between the microwave and the ejected droplets (research: 0.5 ms) which results from the requirement for a small system size for its integration. The primary medium examined for the experiment is water due to 1) a high dielectric loss proportional to the drying efficiency and 2) avoiding explosion risks at the laser sintering stage compared to organic solutions. Various droplet generation conditions were investigated to determine the optimum conditions for the custom droplet generator, in particular, two key parameters were focused on: frequency and flow rate. The droplets obtained were analyzed with respect to size, gap distance, and linearity affecting the uniformity of the AM process. Moreover, Navier-Stokes-based fluid dynamics simulations enabled understanding of droplets behaviors, especially break-up formation. Eventually, the optimal condition for producing the smallest droplets with a diameter of 100 µm is determined to be 15 kHz and 0.5 ml/min. Such droplets loaded with metallic particles could result in smaller than 20 um of remaining metal powders aggregate after the drying process.A new TEM (Transverse ElectroMagnetic) resonator has been developed for drying and sensing applications. A full-wave electromagnetic simulation software, CST Microwave Studio, supported the working mode of the device. Firstly, it is used for the dielectric characterizations of different water-ethanol mixtures contained in a micro capillary. The sensing relies on electric field perturbation due to the inserted sample, and is measured based on the change of both resonance frequency and Q-factor. These sample-dependent variations were analyzed to estimate the complex permittivity using different methods such as the Perturbation Method (PM), Least-Square Model (LSM), and Log-Linear Model (LLM). This work demonstrates that the proposed microwave module is capable of sensing nano-liter volume ranges even though the samples only partially influence the sensing area (error < 13 % in permittivity). In microwave heating, the developed resonator achieved a temperature increase of 28 K in the microwave exposal time of 0.5 ms when the microwave power of 45 W was applied. Finally, numerical models have been proposed to estimate the maximum temperature of the initial droplet before cooling starts attributable to heat and mass transfer. This model well corresponds to the microwave electromagnetic simulation resulting in similar temperature deviations. It helps to determine the net heating efficiency of the microwave device.

EPFL2022

Chargement

Computational Analysis and Methods for Electromagnetic Exposure Limits, Antenna Optimization and Cell Phone Design

Chen Xi Lin

In recent years, the advancements of wireless technologies have led to rapid developments in the field of telecommunication, power delivery and bio-medical applications. During the evolution of a wireless technology, the electromagnetic compatibility (EMC) between a radiating source (e.g., an antenna) and nearby active or passive elements (e.g., a closely integrated electronic component or a human body) often introduces challenging design requirements. This thesis focuses on the applications of state-of-the-art computational electromagnetic compatibility (CEMC) techniques in multidisciplinary engineering design tasks, with an emphasis on computational bio-electromagnetic compatibility (CBEMC). The analyses reported in this thesis span practical applications from power frequency (Hz) to radio frequency (GHz), providing research outcomes which significantly benefit the understandings of low-frequency human body exposure safety and radio-frequency antenna integration and optimization. The research aspect of the thesis is initiated with a thorough review of the existing low-frequency exposure safety guidelines recommended by international regulatory committees. The subsequent analyses suggest essential scientific basis for the update and revision of the existing exposure limits. Practical exposure scenarios (e.g., magnetic resonant wireless power transfer) are investigated with novel assessment techniques. Subsequently, a computer-aided optimization scheme based on network-distributed genetic algorithms is applied to highly detailed numerical mobile phone model and human body phantoms. The investigated optimization technique is proven to be superior than traditional empirical approaches. Finally, the CEMC techniques are applied in the context of non-dosimetry related engineering design environment by investigating the integration of a miniature loudspeaker (acoustic component) and a mobile device antenna (radio frequency component). Based on simulation and measurement data, the coupling mechanisms are determined to establish the fundamental design guidelines for optimum antenna-speaker co-existence and performance. In summary, this thesis details several novel applications of CEMC in the most stringent and complex industrial design environments. The presented research findings serve as indispensable basis for future research oriented towards the exposure-compliant and electromagnetic- compatible designs for novel wireless technologies.

EPFL2013

Chargement

Bulk CMOS technologies left the semiconductor market to the novel device geometries such as FDSOI and FinFET below 30 nm, mainly due to their insufficient electrical characteristics arising from different physical limitations. These innovative solutions enabled the ongoing device scaling to continue. However, the threshold voltage and the power supply values did not shrink with the device sizes, which caused an excessive amount of heat generation in very small dimensions. With the high thermal resistivity materials used in FDSOI and FinFET, the generated heat cannot leave the device easily, which is not the case in bulk. With all of these, modern geometries brought a major problem, which is the self-heating. Due to self-heating effects (SHE), the temperature of a device rises significantly compared to its surroundings. Having very large local temperature brings important reliability issues. Moreover, the electrical behaviour of a device also changes dramatically when its temperature is very large. These facts bring the need of considering SHE and the temperature of each device separately. Nevertheless, in many of today's CAD tools, a single global temperature is applied to all of the devices. Even if some advanced simulation options are used, estimating the temperature of a device is not a simple task as it depends on many parameters. The focus of this thesis is to show the significance of SHE in the design of ICs and provide self-heating aware design guidelines. In order to achieve this, different circuit implementations are studied by considering the SHE. The study consists of two main parts, which are the reliability of the high-speed digital circuits and the performance of analog blocks where noise is critical. Moreover, detailed device-level electro-thermal simulations are performed to explain the self-heating phenomena more in detail and to perform a comparison between bulk and FDSOI. The digital part of the self-heating study is performed on two very high-speed full-custom 64-bit Kogge-Stone adders in 40 nm and 28 nm technologies. Thermal simulations are performed on these blocks to compare SHE in bulk and FDSOI geometries. The comparison of two implementations also provides the increasing significance of SHE with scaling. Extensive heating analyses are performed to find the most critical devices that are the primary heat generators. Design guidelines and solutions are proposed to flatten the temperature profiles in precharged and static logic implementations and to decrease the probability of electromigration. The analog study of the work focuses on the thermal noise performance of LNAs and SHE on the flicker noise. Since thermal noise of a device linearly depends on the temperature, it is directly affected by SHE. To show the amount of SHE on the noise figure, three common gate cascode LNAs operating at 2 GHz with different device lengths are implemented in 28 nm FDSOI. The measurements show that the self-heating effects are clearly observed on the noise figure and the performance of the blocks deviate importantly from the simulations. Moreover, the self-heating effects are significantly more in short channel devices due to their large heat density. Similar experiments are also performed on different test structures in FDSOI at lower frequencies to observe SHE on flicker noise. The experiments show that flicker noise degrades at larger temperatures and more in short channel implementations.

EPFL2018

Chargement