The interaction of a high power, high frequency (HF) pump/electromagnetic (EM) wave transmitted from a ground-based station with the ionosphere, experiments which have been termed "ionospheric heating", produces secondary radiation known as stimulated electromagnetic emissions (SEEs). SEEs have been developed into powerful diagnostics yielding information such as electron temperature, ion species and hydrodynamic evolution of the modified ionospheric plasma. Classic SEEs which exist outside ±1 kHz of the pump wave frequency (ω0) have recently been classified into wideband SEEs (PW-WSEEs) and distinguished from narrowband SEEs (PW-NSEEs) which exist within ±1 kHz of ω0, where the "PW" prefix has been used to indicate that the frequency regimes in the aforementioned classification are relative to the pump wave (PW) frequency. The occurrence of SEEs near 2ω0 is known as second harmonic generation (SHG). SHG is longstanding and well-established in the field of Laser Plasma Interactions (LPI) where SHG has been harnessed to yield diagnostics such as the velocity of the critical region of the plasma, inference of the region in the plasma where the interaction that results in SHG occurs, plasma turbulence and density scale lengths. Past studies of ionospheric heating SHG were limited by the effective radiated power (ERP) available at ionospheric heating facilities and the frequency resolution of receivers/spectrum analyzers of the time. Experimental observations from these past studies reported either SEEs produced as a result of SHG in isolation or compared these SEEs with PW- WSEEs. Moreover, these experiments did not evaluate effects such as transmit ERP, tilt of the transmit antenna beam from the geomagnetic field (B0) and the offset of ω0 from harmonics of the electron gyrofrequency (ωce) on SEEs within a narrowband of twice the pump wave frequency produced as a result of SHG. Also, these studies did not attempt to draw from the knowledge-base on SHG from LPI. The novelty of the experimental observations in this dissertation is the juxtaposition of PW-NSEEs and second harmonic narrowband SEEs (SH-NSEEs), which are SEEs within kHz of 2ω0, measured at the same time. The heating experiments were all performed at HAARP using an O-mode polarized EM pump wave. Additionally, these measurements evaluate the effects on SHG of the transmit ERP, tilt of the transmit station antenna beam from the geomagnetic field (B0) and the offset of ω0 from nωce, n = 2, 3. The experimental observations show, for the first time, a clear association between PW-NSEEs and SH-NSEEs. This association is subsequently used, in conjunction with theories from LPI to propose the non-linear wave-mixing mechanisms responsible for the SH-NSEEs. As a prelude to harnessing the wealth of diagnostics that can be obtained from SHG, initial diagnostics of the velocity of the critical region and the interaction region where SHG occurs are determined using theories from LPI. With the association between PW-NSEEs and SH-NSEEs established, Particle- In-Cell (PIC) simulations are used to investigate the characteristics of a PW- NSEE herein referred to as the "SBS line", produced as a result of stimulated Brillouin scatter (SBS) instability in which the pump EM wave decays into a backscattered EM wave and an ion acoustic wave. The PIC simulations reveal that for high pump powers, the SBS line, which is intense at the onset of the heating experiment, is suppressed within 3 seconds due to the development of cavities in the ionospheric plasma (density) in which the pump wave depletes its energy in heating up electrons. Although, no PIC simulation results of SHG have been presented in this work, the association between PW-NSEEs and SH-NSEEs shown in this work is used to propose that similar mechanisms are responsible for the suppression the SBS line and its associated SH-NSEE for high pump powers. Results from ionospheric heating experiments presented in this dissertation show a rapid suppression of both the SBS line and its associated SH-NSEE for high pump powers. The attribution of the suppression of SH-NSEEs to the development of artificial field-aligned irregularities (AFAIs) in a past study fails to explain the rapid suppression in the experimental observations contained herein since the suppression occurs on a much faster timescale than the development of AFAIs. Thus, the PIC model results have led to a more feasible interpretation of the observed rapid suppression. To re-iterate, the contributions of this dissertation are as follows: 1. First observations of an SH-NSEE named "SH decay line" within 2ω0±30 Hz. The SH decay line occurs at the same transmit power as the SBS line within ω0±30 Hz and both of these SEEs are suppressed for ω0 ≈ 3ωce. Offset of the SH decay line from 2ω0 is twice the offset of the SBS line from ω0. 2. First experimental evaluation of the impact of B0 assessed by stepping the transmit beam offset from B0 and stepping ω0 near 2ωce shows contemporaneous SH-NSEEs and PW-NSEEs both ordered by the O+ ion cyclotron frequency. 3. First experimental observations of suppression of SBS line and SH decay line for high pump powers, which unlike a past study cannot be attributed to AFAIs. 4. First PIC simulation investigation of suppression of SBS line observed during high pump power ionospheric heating, revealing depletion of pump energy in heating electrons in cavities created in the plasma (density) as the mechanism responsible for the suppression. Broadening of SBS line observed in ionospheric heating with high power is also observed in PIC simulation results. This work has laid the foundations to develop SHG into powerful ionospheric diagnostics. / Doctor of Philosophy / When a high power, high frequency radio wave is injected from a ground-based transmit station into the ionosphere, a region of Earth's atmosphere containing charged particles in addition some neutral atoms and molecules, the frequency spectrum measured at a location removed from the transmit station shows emissions at other frequencies in addition to an emission at the transmit frequency. The emissions at these other frequencies are known as stimulated electromagnetic emissions (SEEs). The frequency offsets of SEEs contain information such as the average kinetic energy associated with random motion of electrons, a parameter known as electron temperature and the ion species present in the region of the ionosphere the radio wave is injected into. The occurrence of SEEs near twice the pump wave frequency is known as second harmonic generation. This dissertation presents experimental observations that compare SEEs which exist within ±1 kHz of the transmit frequency with SEEs which exist within a similar frequency range of twice the transmit frequency unlike past studies. This dissertation also investigates effects of varying the transmit frequency, power and the direction of the transmit station antenna beam relative to the local direction of the magnetic field of the Earth. These new studies reveal, for the first time, a similarity in characteristics of the SEEs near the transmit frequency and two times the transmit frequency. This similarity is used in conjunction with theories from studies of Laser Plasma Interaction (LPI), which have corollaries with high power radio wave-ionosphere interaction, to propose the processes that underlie the occurrence of SEEs near twice the transmit frequency. Methods from LPI have also been used for the first time to obtain measurements of some parameters of the ionosphere. High power radio wave-ionosphere interaction experiments are very expensive and moreover, direct measurement of ionospheric parameters/processes require radar facilities which may not be available or sounding rockets or satellites which increase the cost of experiments. Computer simulations offer a facile and an inexpensive means to investigate SEEs and processes internal to the ionosphere. Computer simulations have been used for the first time in this dissertation to investigate the mechanisms responsible for the characteristics of SEEs near the transmit frequency for low and high transmit powers. Since an association has been established in this dissertation between SEEs near the transmit frequency and SEEs near twice the transmit frequency, the mechanisms responsible for the characteristics for the SEEs near the transmit frequency for high transmit power, have been proposed to be the same mechanisms responsible for the characteristics of SEEs near twice the transmit frequency for a similar transmit power regime. The experimental results, computer simulation results and the corollaries drawn between high power radio wave-ionosphere interaction and LPI detailed in this dissertation have opened new doors to develop SEEs near twice the transmit frequency into a powerful tool to study the ionosphere.

Modern gridded ion thrusters for CubeSats operate by generating high power and canpose challenging problems with Electromagnetic Interference (EMI). In order to verifycompatibility with neighbouring equipment, strict standards such as the militarystandard MIL-STD-461G, are required to be followed to achieve ElectromagneticCompatibility (EMC). To avoid abrupt and cataclysmic delays in production time, incase the product fails to comply with the requirements, companies integrate in-housepre-compliance tests into their development phase. The objective is to implementin-house measurement methods on an electric propulsion model NPT30 developedby ThrustMe. This document explains the process and methods to perform conductedemission test on power lines and radiated emission tests in the magneticfield. A custom measurement system integrity verification was developed for theradiated emission test. The presented results provide the engineers at ThrustMe aninsight on the electromagnetic behaviour on the ion thruster NPT30 and whethermodifications need to be included in the next development iteration to mitigate forthe detected excessive emission levels. When EMC methods are implemented earlyon in the development process, there are more pre-emptive mitigation options withless costs in time and money. By performing in-house pre-compliance tests andtaking measures to prepare for the tests at a certified EMC test house, the companycan be more confident in their product at passing the EMC tests. Based on the twoperformed in-house tests, the engineers at ThrustMe began to include mitigationmethods in the following circuit design iterations.

Les convertisseurs de puissance sont largement utilisés de nos jours dans des applications qui demandent une grande autonomie énergétique, comme par exemple ceux qui sont alimentés par des batteries. En particulier, les amplificateurs de type Class-D sont fréquemment utilisés dans les applications audio. Ces amplificateurs commutés ont une architecture ressemblante à celle d'un convertisseur DC-DC, ce qui les permet d'avoir une efficacité énergétique élevée. Cependant, leur inconvénient majeur est la forte émission en perturbations électromagnétiques (EM). Cela peut causer des problèmes de conformité avec les normes de compatibilité électromagnétique (CEM), ou bien perturbé le bon fonctionnement des applications électroniques qui l'entour. Pour cela, ils existent de nombreuses études qui permettent de réduire les émissions d'un amplificateur de Class D. Cependant, cela n'est pas suffisant pour retirer le filtre de CEM. Il est donc nécessaire d'optimiser ces filtres et de faciliter leurs conceptions. Ceci est le but de la présente thèse et il est divisé en quatre grandes parties. La première partie commence par développer une technique de modélisation dans le domaine fréquentiel. Cette technique qui est basée sur la détermination et la manipulation des matrices d'impédances a comme but de simuler et prédire les perturbations EM générées par un amplificateur de Class D. Tous les aspects théoriques de la méthode ont été développés. Ensuite, une application pratique sur un système de Class D dédié à la téléphonie mobile nous a permis de valider la méthode jusqu'à une fréquence de 100 MHz. Un amplificateur de Class D est une source de perturbation aussi bien sur les rails d'alimentation que sur les rails de sortie. Pour cela, le filtre de CEM est nécessaire sur les rails de l'alimentation comme il y est en sortie. Néanmoins, un filtre correctement construit doit être conçu en prenant en compte l'impédance de la charge qui est la batterie dans ce cas. Pour cela, la deuxième partie a pour objectif la mesure de l'impédance de la batterie sur la gamme de fréquence considérée. Ainsi, une technique de mesure d'impédance de batterie en utilisant un impédance mètre est développée. Ensuite, une application expérimentale sur un convertisseur DC-DC et une batterie nous a permis de valider la procédure de mesure. La troisième partie s'est focalisée sur l'optimisation du filtre de CEM. Le modèle fréquentiel développé dans la première partie est intégré dans une boucle d'optimisation basée sur un algorithme génétique. L'optimisation inclus plusieurs critères dans sa fonction objective qui sont l'augmentation de la capacité du filtre à réduire les émissions EM, la diminution des pertes supplémentaires due à l'utilisation du filtre et finalement le gain du filtre dans la bande de fréquence du signal audio. Cette étude est poursuivie par une validation expérimentale. La quatrième et la dernière partie étudie et quantifie les impacts du filtre de CEM sur la qualité audio de l'amplificateur. En effet, le filtre de CEM est l'un des chemins propagation du signal audio. Par suite, tout comportement non linéaire du filtre conduit à la distorsion du signal audio. Pour cela, cette partie est dédiée à la modélisation et la simulation des composants passifs contenant un matériau magnétique. En particulier, l'étude s'est focalisée sur la modélisation des perles de ferrite en utilisant le modèle de matériaux magnétiques Jiles-Aterthon. Les résultats de simulations sont comparés avec la mesure dans le domaine temporel et fréquentiel. En plus, le calcul du taux de distorsion harmonique nous a permis de valider le modèle sur une large plage d'amplitude. / Switching power management circuits are widely used in battery powered embedded applications in order to increase their autonomy. In particular, for audio applications, Class-D amplifiers are a widespread industrial solution. These, have a similar architecture of a buck converter but having the audio signal as reference. The switching nature of these devices allows us to increase significantly the power efficiency compared to linear audio amplifiers without reducing the audio quality. However, because of the switching behavior, Class-D amplifiers have high levels of electromagnetic (EM) emissions which can disturb the surrounding electronics or might not comply with electromagnetic compatibility (EMC) standards. To overcome this problem much architecture appeared in the state of the art that reduces the emissions, however, this has never been enough to remove electromagnetic interference (EMI) filters. It is then useful to optimize these filters, thus, it has been set as the goal of this PhD thesis. The latter has been divided to four main axes which can be resumed by the following. First, this work started by developing a frequency domain modeling method in order to simulate and predict the EMI of Class-D amplifiers in the final application. The method is based on system to block decomposition and impedance matrix modeling and manipulation. After providing all the theoretical background, the method has been validated on integrated differential Class-D amplifier. The experimental measurements have permitted to validate the method only up to 100MHz. However, this is sufficient to cover the conducted EMC frequency band. Second, the EMI at the supply rails of Class-D amplifiers has been treated. As the battery is often the same power supply for all applications in an embedded system, an EMI filter or a decoupling capacitor is needed to prevent the noise coupling by common impedance. Designing this filter needs the knowledge of the battery impedance at the desired frequencies. Therefore the present work dealt also with measuring the high frequency impedance of a battery. Afterwards, an experimental validation has been carried on with a DC-DC converter and a Class-D amplifier. The developed model allows a virtual test of the switching device in the final application. However, it is more useful if the model is able to help the system integrator in designing filters. Thus, third, the model has been implemented in an optimization loop based on a genetic algorithm in order to optimize the filter response, and also, reduce the additional power losses introduced by an EMI filter. The optimization search space has been limited to the components available on the market and the optimization result is given as component references of the optimal filter referring to the optimal solution found. This procedure has been validated experimentally. Finally, EMI filters often are constituted by magnetic components such as ferrite beads or inductors with magnetic cores. Thus, introducing the EMI filter in the audio path, adds a nonlinear behavior in the audio frequency band. Designing a high quality EMI filter require taking into account this phenomenon and studying its impact of the original amplifier audio performance. Therefore, the Jiles-Atherton model for magnetic materials has been used for ferrite bead modeling. Hereafter, the impact on the time and frequency domain signals has been simulated and compared to measurements. Finally, the total harmonic distortion (THD) has been computed for different signal amplitudes and compared to the THD measured using an audio analyzer. Accurate results have been obtained on a wide range of signal amplitudes. As a conclusion, this work aimed to design optimal EMI filters for Class-D amplifiers. Thus, we dealt with improving their EMI response, reducing their additional power losses and evaluating their impact on the audio quality.

<p dir="ltr">Sensing and communication circuits and systems are crucial components in various electronic devices and technologies. These systems are designed to acquire information from the surrounding environment through sensors, process that information, and facilitate communication between different devices or systems. It plays a vital role in modern electronic devices, enabling them to collect, process, and exchange information to perform various functions in applications such as IoB (Internet of Body), healthcare, hardware security, industrial automation, and more.</p><p dir="ltr">This work focuses on innovations in sensing and communication circuits spanning two independent application areas – human body communication and hardware emanations security.</p><p dir="ltr">First, an ultra-low power ECG monitoring system is implemented to perpetually power itself using Thermoelectric Generator (TEG) to harvest body energy while securely transmitting sensed data through on-body communication, achieving closed-loop operation without external charging or batteries. Custom circuits allow demonstrated feasibility of self-sustaining wearables leveraging Human Body Communication’s advantages.</p><p dir="ltr">Second, investigations reveal vulnerabilities introduced when repairing broken cables, with unintended monopole antennas boosting electromagnetic emissions containing signal correlations. Experiments characterize long-range detection regimes post-repair across USB keyboard cables. Further circuit and structural innovations provide localized shielding at repair points as a potential mitigation. Advancements offer contributions in understanding hardware emission security risks to inform protection strategies.</p><p dir="ltr">The two separate research work demonstrate specialized circuits advancing the state-of-the-art in sensing and communication for wearable body-based systems and hardware security through greater awareness of vulnerabilities from unintended emissions.</p><p><br></p>

Au cours de cette thèse, nous nous sommes concentrés sur la sécurité des appareils mobiles. Pour cela, nous avons exploré les attaques physiques par perturbation (injection de fautes) ainsi que par observation, toutes deux basées sur les émissions électromagnétiques. Nous avons sélectionné deux types de cibles représentant deux catégories d'appareils mobiles. D'une part les microcontrôleurs qui équipent les appareils de type IoT. Et d'autre part les System-on-Chip (SoC) que l'on retrouve sur les smartphones. Nous nous sommes concentrés sur les puces conçue par ARM. Au travers d'attaques physiques nous avons voulu montrer qu'il était possible d'affecter la microarchitecture sur laquelle repose tout le fonctionnement de ces systèmes. Toutes les protections pouvant être mises en place par la suite au niveau logiciel, sont basées sur la microarchitecture et deviennent donc inopérantes lorsque l'on s'attaque à celle-ci. Pour les appareils de type IoT, nous avons mis en évidence la possibilité d'obtenir des informations ou un contrôle total de l'appareil à l'aide d'une injection de faute. Les injections de fautes sont dans ce cas les déclencheurs d'attaques logicielles et permettent d'outrepasser des protections logicielles. Pour les appareils de type smartphone, nous avons dans un premier temps été capable d'extraire des informations contenue à l'intérieur d'un SoC, à l'aide d'une écoute électromagnétique et de la caractérisation du comportement de celui-ci. Dans un deuxième temps, nous avons pu montrer qu'en cas de faute des comportements aléatoire peuvent se produire, tout en caractérisant ces comportements. Démontrant ainsi que sur des systèmes plus complexes, il est tout de même possible d'avoir recours à des attaques physiques. Enfin nous avons proposé des pistes d'améliorations en lien avec nos différentes constatations au cours de ces travaux. / During this thesis, we focused on the security of mobile devices. To do this, we explored physical attacks by perturbation (fault injections) as well as by observation, both based on electromagnetic emissions. We selected two types of targets representing two categories of mobile devices. On the one hand, the microcontrollers that equip IoT devices. And on the other hand the System-on-Chip (SoC) that can be found on smartphones. We focused on the chips designed by ARM. Through physical attacks we wanted to show that it was possible to affect the microarchitecture on which the entire functioning of these systems is based. All the protections that can be implemented later at the software level are based on the microarchitecture and therefore become ineffective when it is attacked. For IoT devices, we have highlighted the possibility of obtaining information or total control of the device by means of a fault injection. In this case, fault injections are used as software attack triggers. They also allow software protection to be bypassed. For smartphone devices, we were initially able to extract information contained within a SoC, using electromagnetic listening and characterization of its behavior. In a second step, we were able to show that in the event of a fault, random behaviours can occur, we characterized and proposed explanations for these behaviours. Demonstrating and on systems more advanced than IoT, it is still possible to use physical attacks. Finally, we proposed possible improvements in relation to our various findings during this work.