Modeling EMI Resulting from a Signal Via Transition Through Power/Ground Layers

Signal transitioning through layers on vias are very common in multi-layer printed circuit board (PCB) design. For a signal via transitioning through the internal power and ground planes, the return current must switch from one reference plane to another reference plane. The discontinuity of the return current at the via excites the power and ground planes, and results in noise on the power bus that can lead to signal integrity, as well as EMI problems. Numerical methods, such as the finite-difference time-domain (FDTD), Moment of Methods (MoM), and partial element equivalent circuit (PEEC) method, were employed herein to study this problem. The modeled results are supported by measurements. In addition, a common EMI mitigation approach of adding a decoupling capacitor was investigated with the FDTD method

Application of PEEC modeling for the development of a novel multi-gigahertz test interface with fine pitch wafer level package

Ph.DDOCTOR OF PHILOSOPH

Automated Construction of Equivalent Electrical Circuit Models for Electromagnetic Components and Systems

The description of electromagnetic components and systems by electrical circuit models is indispensable for a wide range of applications: In the field of EMC, electrical circuit models are ideally suited for the detection of EMC coupling paths, which are very difficult to track for 3D geometries. In the field of numerical optimization techniques, electrical circuit models offer short simulation times and allow the coupling of the electromagnetic domain to other physical domains. In the field of power electronics, electrical circuit models describe energy dissipation due to parasitic electromagnetic interactions. The construction of an equivalent electrical circuit model is in general cumbersome and less formalized than a description in terms of electromagnetic fields. No general and reliable technique for the automated construction of equivalent electrical circuit models exists. The aim of this thesis is the development of a technique that allows a fully automated construction of equivalent electrical circuit models from 3D geometry information. Instead of constructing the circuit directly from geometry data, our approach consists of reducing a field-theoretical model to an equivalent electrical circuit model. In this way, we exploit the generality of the field-theoretical approach, which can be applied for a wide range of geometries using state-of-the-art simulation techniques. The electromagnetic effects having the largest impact in the frequency range of interest are then used for the construction of the electrical circuit model. The circuit elements can be seen as condensed representations of these field-theoretical processes. The reduction process allows a very direct assessment of the accuracy of the electrical circuit model

13th Annual Review of Progress in Applied Computational Electromagnetics at the Naval Postgraduate School, Monterey, CA, March 17-21, 1997, Conference Proceedings Volumes I & II

Includes Volumes 1 &

Annual Review of Progress in Applied Computational Electromagnetics

Approved for public release; distribution is unlimited

Safety of Simultaneous Scalp and Intracranial Electroencephalography Functional Magnetic Resonance Imaging

Understanding the brain and its activity is one of the great challenges of modern science. Normal brain activity (cognitive processes, etc.) has been extensively studied using electroencephalography (EEG) since the 1930’s, in the form of spontaneous fluctuations in rhythms, and patterns, and in a more experimentally-driven approach in the form of event-related potentials allowing us to relate scalp voltage waveforms to brain states and behaviour. The use of EEG recorded during functional magnetic resonance imaging (EEG-fMRI) is a more recent development that has become an important tool in clinical neuroscience, for example, for the study of epileptic activity. The primary aim of this thesis is to devise a protocol in order to minimise the health risks that are associated with simultaneous scalp and intracranial EEG during fMRI (S- icEEG-fMRI). The advances in this technique will be helpful in presenting a new imaging method that will allow the measurement of brain activity with unprecedented sensitivity and coverage. However, this cannot be achieved without assessing the safety implications of such a technique. Therefore, five experiments were performed to fulfil the primary aim. First, the safety of icEEG- fMRI using body transmit RF coil was investigated to improve the results of previous attempts using a head transmit coil at 1.5T. The results of heating increases during a high-SAR sequence were in the range of 0.2-2.4 °C at the contacts with leads positioned along the central axis inside the MRI bore. These findings suggest the need for careful lead placement. Second, also for the body transmit coil we compared the heating in the vicinity of icEEG electrodes placed inside a realistically-shaped head phantom following the addition of scalp EEG electrodes. The peak temperature change was +2.7 °C at the most superior icEEG electrode contact without scalp electrodes, and +2.1 °C at the same contact and the peak increase in the vicinity of a scalp electrode contact was +0.6 °C (location FP2). These findings show that the S-icEEG-fMRI technique is feasible if our protocol is followed carefully. Third, the heating of a realistic 3D model of icEEG electrode during MRI using EM computational simulation was investigated. The resulting peak 10 g averaged SAR was 20% higher than without icEEG. Moreover, the superior icEEG placed perpendicular to B0 showed significant local SAR increase. These results were in line with previous studies. Fourth, the possibility of simplifying a complete 8-contact with 8 wires depth icEEG electrode model into an electrode with 1-contact and 1 wire using EM simulations was addressed. The results showed similar patterns of averaged SAR values around the electrode tip during phantom and electrode position along Z for the Complete and Simplified models, except an average maximum at Z = ~2.5 W/kg for the former. The SAR values during insertion depth for the Simplified model were double those for the Complete model. The effect of extension cable length is in agreement with previous experiments. Fifth, further simulations were implemented using two more simplified models: 8-contact with 1 wire shared with all contact and 8-contact 1 wire connected to each contact at a time as well as the previously modelled simplified 1-contact 1 wire. Two sets of simulations were performed: with a single electrode and with multiple electrodes. For the single electrode, three scenarios were tested: the first simplified model used only, the second simplified models used only and the third model positioned in different 13 locations. The results of these simulations showed about 11.4-20.5-fold lower SAR for the first model than the second and 0.29-5.82-fold lower SAR for the first model than the complete model. The results also showed increased SAR for the electrode close to the head coil than the ones away from it. For the multiple electrodes, three scenarios were tested: two 1-contact and wire electrodes in different separations, multiple electrodes with their wires separated and multiple electrodes with their wires shorted. The results showed interaction between the two tested electrodes. The results of the multiple electrodes presented 2 to ~10 times higher SAR for the separated setup than the shorted. The comparison between the 1-contact with 1 wire model and the complete model is still unknown and more tests are required to show it. From the findings of this PhD research, we conclude that a body RF coil can be utilized for icEEG-fMRI at 1.5 T; however, the safety protocol has to be implemented. In addition, scalp EEG can be used in conjunction with icEEG electrodes inside the body RF coil at 1.5 T and the safety protocol has to be followed. Finally, it is feasible to perform EM computational simulations using realistic icEEG electrodes on a human model. However, simplifying the realistic icEEG electrode model might result in overestimations of the heating, although it is possible that the simplification of the model can help to simulate more complex implantations such as the implantation of multiple electrodes with their leads open circuited or short circuited, which can provide more information about the safety of implanted patients inside the MRI

Agile and Bright Intracardiac Catheters

Intracardiac imaging catheters represent unique instruments to diagnose and treat a diseased heart. While there are imminent advances in medical innovation, many of the commercially available imaging catheters are outdated. Some of them have been designed more than 20 years and therefore they lack novel sensor technology, multi-functionality, and often require manual assembly process. Introduction chapter of this thesis discusses clinical needs and introduces new technological concepts that are needed to progress the functionality and clinical value of the intracardiac catheters along with efficient and simple designs to make the catheters affordable for the patients. The following chapters are grouped into two parts that explore complementary transducer technology and a novel optical fiber-link solution for catheter-based intracardiac imaging. _Part I_ focuses on developing a new intracardiac catheter that has an advanced functionality, which provides clinician with high penetration or close-up high resolution ultrasound imaging in a single device. This agile ultrasound visualization is enabled by a capacitive-micromachined ultrasound transducer (CMUT), operated in collapse-mode, of which the operating frequency can be tuned. Acoustic performance of a fabricated CMUT is modelled and measured. Imaging performance of the CMUT array is quantified on a tissue-mimicking phantom and demonstrated both ex vivo and in vivo experiments. It is found that the combination of the forward-looking design, frequency-tuning and agile deflectability of the catheter allow for visualizing intracardiac structures of various sizes at different distances relative to the catheter tip, providing both wide overviews and detailed close-ups. _Part II_ is devoted to a novel optical technology for transmitting signals and transferring power inside catheters. A novel concept of an all-optical fiber link is introduced. A key insight obtained is that a blue light-emitting diode (LED) may be used as a photo-voltaic converter. Used in reverse under illumination with violet light, it converts significant amount of photonic energy to electricity and at the same time it may emit blue light back, which makes it a unique miniature power and communication channel for catheters. A pressure-sensing catheter prototype is built to demonstrate the concept of transmitting signals and delivering power using a single optical fiber and an LED. The potential of the power and signal fiber link solution is exploited further for ultrasound imaging. A bench-top demonstrator scalable to catheter dimensions is built, in which electrical wires for ultrasound-sensor signal and power tra

Analyse et caractérisation des couplages substrat et de la connectique dans les circuits 3D : Vers des modèles compacts

The 3D integration is the most promising technological solution to track the level of integration dictated by Moore's Law (see more than Moore, Moore versus more). It leads to important research for a dozen years. It can superimpose different circuits and components in one box. Its main advantage is to allow a combination of heterogeneous and highly specialized technologies for the establishment of a complete system, while maintaining a high level of performance with very short connections between the different circuits. The objective of this work is to provide consistent modeling via crossing, and / or contacts in the substrate, with various degrees of finesse / precision to allow the high-level designer to manage and especially to optimize the partitioning between the different strata. This modelization involves the development of multiple views at different levels of abstraction: the physical model to "high level" model. This would allow to address various issues faced in the design process: - The physical model using an electromagnetic simulation based on 2D or 3D ( finite element solver ) is used to optimize the via (materials, dimensions etc..) It determines the electrical performance of the via, including high frequency. Electromagnetic simulations also quantify the coupling between adjacent via. - The analytical compact of via their coupling model, based on a description of transmission line or Green cores is used for the simulations at the block level and Spice type simulations. Analytical models are often validated against measurements and / or physical models.L’intégration 3D est la solution technologique la plus prometteuse pour suivre le niveau d’intégration dictée par la loi de Moore (cf. more than Moore, versus more Moore). Elle entraine des travaux de recherche importants depuis une douzaine d’années. Elle permet de superposer différents circuits et composants dans un seul boitier. Son principal avantage est de permettre une association de technologies hétérogènes et très spécialisées pour la constitution d’un système complet, tout en préservant un très haut niveau de performance grâce à des connexions très courtes entre ces différents circuits. L’objectif de ce travail est de fournir des modélisations cohérentes de via traversant, ou/et de contacts dans le substrat, avec plusieurs degrés de finesse/précision, pour permettre au concepteur de haut niveau de gérer et surtout d’optimiser le partitionnement entre les différentes strates. Cette modélisation passe par le développement de plusieurs vues à différents niveaux d’abstraction: du modèle physique au modèle « haut niveau ». Elle devait permettre de répondre à différentes questions rencontrées dans le processus de conception :- le modèle physique de via basé sur une simulation électromagnétique 2D ou 3D (solveur « éléments finis ») est utilisé pour optimiser l’architecture du via (matériaux, dimensions etc.) Il permet de déterminer les performances électriques des via, notamment en haute fréquence. Les simulations électromagnétiques permettent également de quantifier le couplage entre via adjacents. - le modèle compact analytique de via et de leur couplage, basé sur une description de type ligne de transmission ou noyaux de Green, est utilisé pour les simulations au niveau bloc, ainsi que des simulations de type Spice. Les modèles analytiques sont souvent validés par rapport à des mesures et/ou des modèles physiques

Nonlinear dynamics in chiral torsional metamaterials

The advent and rapid development of metamaterials introduced many revolutionary concepts for manipulating electromagnetic waves. As an important class of metamaterials, chiral metamaterials allow us to control the polarization of electromagnetic waves at the subwavelength scale. While much work has been done on using chiral metamaterials to control electromagnetic waves, the accompanying effects, such as the electromagnetic force and torque acting on the structures, as well as nonlinear optomechanical effects, are still largely unexplored. The exploration of these areas could provide useful insight from both fundamental and practical points of view. In this thesis, we study new properties of chiral metamaterials, in particular the optomechanical properties and nonlinear effects that arise from the coupling between electromagnetic and elastic degrees of freedom. An accurate and efficient model based on the free-space Green’s function under the eigenmode approximation is developed for the study. In Chapter 1, we provide a comprehensive introduction to the basic concepts and history of metamaterials, followed by more focused reviews on chiral metamaterials, different paradigms of tunable metamaterials, the nontrivial electromagnetic force and torque, as well as the nonlinear optomechanical effect in different platforms. Finally, the motivation and the scope of the thesis are summarized. To understand the optical activity in coupled structures, in Chapter 2, we employ the model developed to study the near-field coupling, far-field scattering and optical activity of chiral meta-molecules based on twisted coupled cut-wire pairs. The numerical results from our model agree well quantitatively with full-wave calculation. We also discuss the optimum twist angle of the structure. After exploring the optical activity, in Chapter 3, we study the optomechanical properties of chiral meta-molecules based on a pair of twisted split-ring resonators. This structure can provide a strong and tunable torque, and can support different optomechanical dynamics, making it a good candidate for subwavelength light-driven actuators. To achieve strong coupling between electromagnetic resonance and elastic deformation in metamaterials, in Chapter 4, we introduce chiral torsional meta-molecules based on twisted split-ring pairs. We predict a rich range of nonlinear stationary effects including self-tuning and bistability. Importantly, these nonlinear effects including bistability are successfully observed in experiment. After understanding the nonlinear stationary responses of torsional meta-molecules, in Chapter 5, we study their nontrivial nonlinear dynamic effects. We introduce a simple structure based on three connected split-rings and find that this structure can support novel nonlinear dynamics such as chaos, damping-immune self-oscillations and dynamic nonlinear optical activity. To understand how intermolecular interaction can change system dynamics, in Chapter 6, we study the nonlinear effects of ensembles of enantiomeric torsional meta-molecules. We find that spontaneous chiral symmetry breaking can exist due to intermolecular interaction. For the first time in metamaterials, both spontaneous chiral symmetry breaking and self-oscillations are successfully demonstrated experimentally. Our study provides a new route to achieve artificial phase transitions in metamaterials without using naturally occurring phase change materials. In Chapter 7, we summarize the work and discuss the future possible topics in related to the optomechanical effects in metamaterials

1-D broadside-radiating leaky-wave antenna based on a numerically synthesized impedance surface

A newly-developed deterministic numerical technique for the automated design of metasurface antennas is applied here for the first time to the design of a 1-D printed Leaky-Wave Antenna (LWA) for broadside radiation. The surface impedance synthesis process does not require any a priori knowledge on the impedance pattern, and starts from a mask constraint on the desired far-field and practical bounds on the unit cell impedance values. The designed reactance surface for broadside radiation exhibits a non conventional patterning; this highlights the merit of using an automated design process for a design well known to be challenging for analytical methods. The antenna is physically implemented with an array of metal strips with varying gap widths and simulation results show very good agreement with the predicted performance