Design of Beam Steering Electronic Circuits for Medical Applications

This thesis deals with the theory and design of a hemispherical antenna array circuit that is capable to operate in the intermediate zones. By doing that, this array can be used in Hyperthermia Treatment for Brain Cancer in which the aim is to noninvasively focus the fields at microwave frequencies to the location of the tumor cells in the brain. Another possible application of the array is to offer an alternative means of sustaining Deep Brain Stimulation other than using the traditional (surgical) approach. The new noninvasive technique is accomplished by the use of a hemispherical antenna array placed on the human's head. The array uses a new beamforming technique that achieves 3 dimensional beamforming or focusing of the magnetic field of antennas to desired points in the brain to achieve either cell death by temperature rise (Hyperthermia Application) or to cause brain stimulation and hopefully alleviate the affects of Parkinson's Disease (Deep Brain Stimulation). The main obstacle in this design was that the far field approximation that is usually used when designing antenna arrays does not apply in this case since the hemispherical array is in close proximity to where the magnetic field is desired to be focused. The antenna array problem is approached as a boundary-valued problem with the human head being modeled as a three layered hemisphere. The exact expressions for electromagnetic fields are derived. Health issues such as electric field exposure and specific absorption rate (SAR) are considered. After developing the main antenna and beamforming theory, a neural network is designed to accomplish the beamforming technique used. The radio-frequency (RF) transmitter was designed to transmit the fields at a frequency of 1.8 GHz. The antenna array can also be used as a receiver. The antenna and beamforming theory is presented. A new reception technique is shown which enables the array to receive multiple magnetic field sources from within the hemispherical surface. The receiver is designed to operate at 500 kHz with the RF receiver circuit designed to receive any signal from within the hemispherical surface at a frequency of 500 kHz

Binaural Reproduction of Higher Order Ambisonics - A Real-Time Implementation and Perceptual Improvements

During the last decade, Higher Order Ambisonics has become a popular way of capturing and reproducing sound fields. It can be combined with the theory of spherical microphone arrays to record sound fields, and this three-dimensional audio format can be reproduced with loudspeakers or headphones and even rotated around the listener. A drawback is that near perfect reproduction is only possible inside a sphere of radius r given by kr < N, where N is the Ambisonics order and k is the wavenumber. In this thesis, the theory of spherical harmonics and Higher Order Ambisonics has been reviewed and expanded, which serves as a foundation for a real-time system that was implemented. This system can record signals from a commercial spherical microphone array, convert them to the Higher Order Ambisonics format, and reproduce the sound field through headphones. To compensate for head motion, a head-tracking device is used. The real-time system operates with a latency of around 95 milliseconds between head motion and consequent sound field rotation. Further, two new methods for improving the headphone reproduction were assessed. These methods do not need to be applied in real-time, so no further system resources are used. Simulations of headphone reproduction with Higher Order Ambisonics show that both methods yield quantitative improvements in binaural cues such as the Interaural Level Difference, spectral cues and spectral coloration of the sound field. Median error values are reduced as much as 50 % between 4 and 7 kHz. The findings indicate that Higher Order Ambisonics reproduction over headphones can be improved at frequencies above limit frequency given by kr < N, but these findings need to be confirmed by subjective assessments, such as listening tests. The work conducted in this thesis has also resulted in a comprehensive basis for further development of a real-time three-dimensional audio reproduction system

Mathematical modelling ano optimization strategies for acoustic source localization in reverberant environments

La presente Tesis se centra en el uso de técnicas modernas de optimización y de procesamiento de audio para la localización precisa y robusta de personas dentro de un entorno reverberante dotado con agrupaciones (arrays) de micrófonos. En esta tesis se han estudiado diversos aspectos de la localización sonora, incluyendo el modelado, la algoritmia, así como el calibrado previo que permite usar los algoritmos de localización incluso cuando la geometría de los sensores (micrófonos) es desconocida a priori. Las técnicas existentes hasta ahora requerían de un número elevado de micrófonos para obtener una alta precisión en la localización. Sin embargo, durante esta tesis se ha desarrollado un nuevo método que permite una mejora de más del 30\% en la precisión de la localización con un número reducido de micrófonos. La reducción en el número de micrófonos es importante ya que se traduce directamente en una disminución drástica del coste y en un aumento de la versatilidad del sistema final. Adicionalmente, se ha realizado un estudio exhaustivo de los fenómenos que afectan al sistema de adquisición y procesado de la señal, con el objetivo de mejorar el modelo propuesto anteriormente. Dicho estudio profundiza en el conocimiento y modelado del filtrado PHAT (ampliamente utilizado en localización acústica) y de los aspectos que lo hacen especialmente adecuado para localización. Fruto del anterior estudio, y en colaboración con investigadores del instituto IDIAP (Suiza), se ha desarrollado un sistema de auto-calibración de las posiciones de los micrófonos a partir del ruido difuso presente en una sala en silencio. Esta aportación relacionada con los métodos previos basados en la coherencia. Sin embargo es capaz de reducir el ruido atendiendo a parámetros físicos previamente conocidos (distancia máxima entre los micrófonos). Gracias a ello se consigue una mejor precisión utilizando un menor tiempo de cómputo. El conocimiento de los efectos del filtro PHAT ha permitido crear un nuevo modelo que permite la representación 'sparse' del típico escenario de localización. Este tipo de representación se ha demostrado ser muy conveniente para localización, permitiendo un enfoque sencillo del caso en el que existen múltiples fuentes simultáneas. La última aportación de esta tesis, es el de la caracterización de las Matrices TDOA (Time difference of arrival -Diferencia de tiempos de llegada, en castellano-). Este tipo de matrices son especialmente útiles en audio pero no están limitadas a él. Además, este estudio transciende a la localización con sonido ya que propone métodos de reducción de ruido de las medias TDOA basados en una representación matricial 'low-rank', siendo útil, además de en localización, en técnicas tales como el beamforming o el autocalibrado

Robust Multichannel Microphone Beamforming

In this thesis, a method for the design and implementation of a spatially robust multichannel microphone beamforming system is presented. A set of spatial correlation functions are derived for 2D and 3D far-field/near-field scenarios based on von Mises(-Fisher), Gaussian, and uniform source location distributions. These correlation functions are used to design spatially robust beamformers and blocking beamformers (nullformers) designed to enhance or suppress a known source, where the target source location is not perfectly known due to either an incorrect location estimate or movement of the target while the beamformers are active. The spatially robust beam/null-formers form signal and interferer plus noise references which can be further processed via a blind source separation algorithm to remove mutual components - removing the interference and sensor noise from the signal path and vice versa. The noise reduction performance of the combined beamforming and blind source separation system approaches that of a perfect information MVDR beamformer under reverberant conditions. It is demonstrated that the proposed algorithm can be implemented on low-power hardware with good performance on hardware similar to current mobile platforms using a four-element microphone array

Metamorphic stretchable electronics

Die jüngsten Fortschritte auf dem Gebiet der Elektronik wenden sich der Realisierung mechanischer dehnbarer Elektroniken zu. Diese sind in der Lage sich umzuwandeln um neue Formfaktoren anzunehmen. Um eine nahtlose Integration der Elektronik in unsere Alltagsgegenstände und viele weitere Anwendungsfelder zu ermöglichen, bei denen herkömmliche starre elektronische Systeme nicht ausreichen, ist mechanische Dehnbarkeit notwendig. Diese Arbeit zielt darauf ab, eine dehnbare Leiterplattentechnologie (sPCB) zu demonstrieren, die mit industriellen Herstellungsprozessen kompatibel ist. Idealerweise soll das starre Trägersubstrat der konventionellen Elektronik durch ein dehnbares Gummisubstrat mit dehnbaren Leiterbahnen ersetzt werden. Zunächst wurde eine Methode entwickelt, um eine industrietaugliche, einlagige, dehnbare Leiterplatte zu realisieren. Der dargestellte Ansatz unterscheidet sich von anderen Methoden in diesem Bereich, welche die Metallisierung auf dem Gummisubstrat aufbringen und die Komponenten anschließend darauf montieren. Dadurch leiden diese unter einer geringeren Ausrichtung und Fixierung. Stattdessen wird im dargestellten Ansatz ein harter Träger verwendet, der den Einsatz des dehnbaren Gummimaterials bis ans Ende der Prozesskette verschiebt. Diese Single-Layer-Methode wurde weiterentwickelt, um mehrschichtige, integrierte sPCB zu realisieren, bei der verschiedene Metallisierungsebenen durch vertikalen Durchkontaktierungen (VIA) miteinander verbunden werden. Auch dieses Verfahren verwendet konventionelle starre Träger für den Herstellungsprozess. Wie in der konventionellen Leiterplattentechnologie ist auch die Herstellung auf starren Trägern wichtig, da sie Folgendes ermöglicht: Ausrichtung und Registrierung, Hochtemperaturprozesse, konventionelle Chip-Bestückung durch Roboter und "On-Hard-Carrier"-Bauteiltests. Darüber hinaus ermöglicht die dargestellte Methode den direkten Einsatz handelsüblicher SMDs, was für die einfache Realisierung komplexer elektronischer Schaltungen wichtig ist. Als Endsubstrat kommt ein hochelastisches Silikonmaterial (EcoFlex) zum Einsatz, welches die Bauelementebenen einkapselt. Um die Bauelementebenen vom harten Träger auf das weiche Substrat zu übertragen, wird ein einstufiges, waferbasiertes und lösungsmittelfreies Ablöseverfahren eingesetzt, bei dem die differentielle Grenzflächenadhäsion einer Multi-Opferschichten genutzt wird. Für die hochelastischen Leiterbahnen wurde ein neues Mäander-Metallbahndesign entwickelt, welches als "spannungsadaptiv" bezeichnet wird. Die neue Mäander-Metallbahn variiert in ihrer Breite, um das einwirkende Drehmoment in den Metallbahnen, aufgrund der ungleichmäßigen Spannungsverteilung über die Mäander-Schleifen, aufzunehmen. Das spannungsadaptive Design zeigt eine signifikante Verbesserung der Spannungsverteilungen auf den Metallbahnen und führt experimentell zu einem höheren Niveau der maximalen Dehnung und der Anzahl der Dehnungszyklen. Es wurde eine breite Palette von dehnbaren Systemen demonstriert, darunter Elektronik, Optoelektronik, Akustoelektronik und Sensor-Arrays. Die Demonstratoren, auf Basis einer einzigen Metallisierungsschicht in einer Gummimatrix, enthalten Arrays mit gehäusten SMDs, LED-Nacktchips, laborgefertigte Si [my]-Transistoren und MEMS-Mikrofone. Weiterhin wird eine integrierte Multilayer-sPCB mit Chip-großen LEDs und Transistoren demonstriert, um eine adressierbare aktive Matrix zu realisieren. Dieser Prototyp demonstriert die Machbarkeit von integrierten Multilayer-sPCB und wird im Prinzip dazu führen, dass jedes heute bekannte elektronische System in ein äquivalentes dehnbares System überführt werden kann. Schließlich stellt diese Arbeit das bahnbrechende Konzept der metamorphen Elektronik vor, welche sich umwandeln kann um neue Topologien und Formfaktoren anzunehmen. Es werden verschiedene Arten von Deformationsmechanismen demonstriert, darunter das Aufblasen von gleichförmigen oder strukturierten Gummimembranen, 3D-geführte Deformationen und Vakuumformung in Kombination mit 3D-Schablonen. Die Palette der Topologien reicht dabei von halbkugelförmig, kugelförmig, konkav/konvex, pyramidenförmig, turmartig, bis hin zu komplexeren 3D-Formen, darunter Bienenaugen-Strukturen.Recent advancement in the field of electronics has taken a shift to enable the realization of mechanically stretchable electronics which morph to take on new form factors. Mechanical stretchability is necessary to have seamless integration of electronics in our daily life objects and many other purposes where conventional rigid electronic system is insufficient. This thesis aims to enable a stretchable printed circuit board (sPCB) technology that is compatible with industrial manufacturing. Ideally, the rigid carrier substrate of conventional electronics is intended to be replaced by stretchable rubber substrate with stretchable interconnects. Initially, a method has been developed to realize an industry compatible single layer stretchable PCB. The approach is different from other reported methods in this field, which apply the metallization to the rubber support and mount the components on top and, which suffer from a lower level of alignment and fixation. Instead, in the depicted method a hard carrier is used, which delays the use of the stretchable rubber support to the end of the processing sequence. The single layer method has been further developed to realize a multilayer integrated sPCB, where different metallization layers are connected through vertical interconnect access (VIA). The method uses hard carrier. Like conventional PCB technology, the hard carrier fabrication is important since it enables: alignment and registration, high temperature processing, conventional robotic chip placement, and “on-hard-carrier” device tests. Moreover, the depicted method enables direct use of commercially available SMDs which is important to realize complex electronic devices. As final substrate, highly stretchable silicone material (EcoFlex) is used which encapsulates the device layers. To transfer the device layers from hard carrier to soft substrate a single-step, wafer-level, and solvent-free detachment process has been developed which uses the differential interfacial adhesion in between the sacrificial layers. For highly stretchable interconnects a new meander metal track design is developed which is named as “stress adaptive” metal track. The new meander metal track varies in widths to accommodate produced torque in the metal tracks due to the non-uniform stress distribution over the meander loops. The stress adaptive design shows a significant improvement in the stress distributions over the metal tracks in computer simulated stress profile. And, experimental results show a higher level of maximum stretching (320%) and higher number of stretch-release cycles (11000) comparing with a reference design. A wide range of stretchable systems have been demonstrated including electronics, optoelectronics, acoustoelectronics and sensor arrays. The demonstrators contain arrays with packaged SMDs, bare dies integrated LEDs, lab-fabricated Si µ-transistors and MEMS microphones using a single metallization layer within a rubber matrix. Furthermore, an integrated multilayer sPCB is demonstrated using chip scale LEDs and transistors to realize an addressable active matrix. These prototypes of integrated multilayer electronics demonstrate method to enable multilayer sPCB technology which could lead to realize any electronic system known today to be stretchable. Finally, this thesis introduces a new type of electronics which morph to adapt to new topology and form factor. This shape-adaptive electronics is named as metamorphic electronics. Various types of deformation mechanisms have been demonstrated including inflation and/or deflation of uniform or patterned rubber membranes, 3D guided deformations, and vacuum forming in combination with 3D chaperons. The range of topologies includes hemispherical, spherical, concave/convex, pyramid, tower, bumble bee-eye, and more complex 3D shapes

Theory and Design of Spatial Active Noise Control Systems

The concept of spatial active noise control is to use a number of loudspeakers to generate anti-noise sound waves, which would cancel the undesired acoustic noise over a spatial region. The acoustic noise hazards that exist in a variety of situations provide many potential applications for spatial ANC. However, using existing ANC techniques, it is difficult to achieve satisfying noise reduction for a spatial area, especially using a practical hardware setup. Therefore, this thesis explores various aspects of spatial ANC, and seeks to develop algorithms and techniques to promote the performance and feasibility of spatial ANC in real-life applications. We use the spherical harmonic analysis technique as the basis for our research in this work. This technique provides an accurate representation of the spatial noise field, and enables in-depth analysis of the characteristics of the noise field. Incorporating this technique into the design of spatial ANC systems, we developed a series of algorithms and methods that optimizes the spatial ANC systems, towards both improving noise reduction performance and reducing system complexity. Several contributions of this work are: (i) design of compact planar microphone array structures capable of recording 3D spatial sound fields, so that the noise field can be monitored with minimum physical intrusion to the quiet zone, (ii) derivation of a Direct-to-Reverberant Energy Ratio (DRR) estimation algorithm which can be used for evaluating reverberant characteristics of a noisy environment, (iii) propose a few methods to estimate and optimize spatial noise reduction of an ANC system, including a new metric for measuring spatial noise energy level, and (iv) design of an adaptive spatial ANC algorithm incorporating the spherical harmonic analysis technique. The combination of these contributions enables the design of compact, high performing spatial ANC systems for various applications

Application de l'holographie acoustique en soufflerie par mesures LDV

L Holographie acoustique de champ proche (NAH) est une méthode d imagerie acoustique robuste, mais son application en écoulement peut être limitée par l utilisation de mesures intrusives de pression ou de vitesse acoustique. Dans cette étude, une procédure holographique applicable en écoulement utilisant des mesures de vitesse non-intrusives est proposée. Cette méthode est basée sur le théorème intégral de Kirchhoff-Helmholtz convecté. La fonction de Green convectée est alors utilisée pour déterminer des propagateurs spatiaux convectés définis dans l espace réel et incluant l effet d un écoulement subsonique uniforme. Les transformées de Fourier discrètes de ces propagateurs permettent alors d évaluer les champs acoustiques à partir de la mesure du champ de pression ou de vitesse acoustique normale. Le but étant de développer une méthode de caractérisation de sources aéroacoustiques à partir de mesures de vitesse non-intrusives, cette étude se concentre essentiellement sur les propagateurs réels convectés basés sur la mesure de vitesse acoustique. Afin de valider cette procédure,des simulations ont été menées dans le cas de combinaisons de sources monopolaires et dipolaires convectées corrélées ou non. La procédure holographique développée donne de bons résultats par comparaison aux champs acoustiques théoriques. Une comparaison des résultats obtenus par les propagateurs convectés réels, développés dans cette thèse, avec ceux obtenus par leurs formes spectrales, développés par Kwon et al. fin 2010 pour des mesures de pression acoustique, montre l intérêt d utiliser la forme réelle pour la reconstruction de la pression acoustique à partir de la mesure de vitesse acoustique normale. L efficacité de la procédure développée est confirmée par une campagne de mesure en soufflerie avec un haut-parleur affleurant rayonnant au sein d un écoulement à Mach 0.22, et des mesures non-intrusives effectuées par Vélocimétrie Laser Doppler (LDV). Les champs de vitesse acoustique utilisés pour la procédure holographique sont dans ce cas extraits des mesures LDV par corrélation avec un microphone de référence. La faisabilité de prendre en compte des variations de l écoulement dans la direction de reconstruction holographique est également vérifiée.Nearfield Acoustic Holography (NAH) is a powerful acoustic imaging method but its application in flow can be limited by intrusive measurements of acoustic pressure or velocity. In this work, a moving fluid medium NAH procedure using non-intrusive velocity measurements is proposed. This method is based on the convective Kirchhoff-Helmholtz integral formula. The convective Green s function is then used to derive convective realspace propagators including uniform subsonic airflow effects. Discrete Fourier transforms of these propagators allow then the assessment of acoustic fields from acoustic pressure or normal acoustic velocity measurements. As the aim is to derive an aeroacoustic sources characterisation method from non-inrusive velocity measurements, this study is especially focused on real convective velocity-based propagators. In order to validate this procedure, simulations in the case of combinations of monopolar and dipolar sources correlated or not, radiating invarious uniform subsonic flows, have been performed. NAH provides very favorable results when compared to the theoretical fields. A comparison of results obtained by real convective propagators, developed in this work, and those obtained by the spectral ones, developed by Kwon et al. at the end of 2010 for acoustic pressure measurements, shows the interest of using the real-form for NAH acoustic pressure reconstruction from normal acoustic velocity measurements. The efficiency of the developed procedure is confirmed by a wind tunnel campaign with a flush-mounted loudspeaker radiating in a flow at Mach 0.22 and non-intrusive Laser Doppler Velocimetry (LDV) measurements. Acoustic velocity fields used for the NAH procedure are in this case extracted from LDV measurements by correlation with a reference microphone. The feasibility of taking into account mean flow variations in the direction of NAH reconstruction is also checked.TOULOUSE-ISAE (315552318) / SudocSudocFranceF