Tesi sul tema "Passive Beamforming"

Radio-frequency identification (RFID) technology is on the way to substitute traditional bar codes in many fields of application. Especially the availability of passive ultra-high frequency (UHF) RFID transponders (or tags) in the frequency band between 860 MHz and 960 MHz has fostered the global application in supply chain management. However, the full potential of these systems will only be exploited if the identification of objects is complemented by accurate and robust localization. Passive UHF RFID tags are cost-effective, very small, extremely lightweight, maintenancefree, rugged and can be produced as adhesive labels that can be attached to almost any object. Worldwide standards and frequency regulations have been established and a wide infrastructure of identification systems is operated today. However, the passive nature of the technology requires a simple communication protocol which results in two major limitations with respect to its use for localization purposes: the small signal bandwidth and the small allocated frequency bandwidth. In the presence of multipath reflections, these limitations reduce the achievable localization accuracy and reliability. Thus, new methods have to be found to realize passive UHF RFID localization systems which provide sufficient performance in typical multipath situations. In this thesis, an enhanced transmission channel model for passive UHF RFID localization systems has been proposed which allows an accurate estimation of the channel behaviour to multipath. It has been used to design a novel simulation environment and to identify three solutions to minimize multipath interference: a) by varying the channel interface parameters, b) by applying diversity techniques, c) by installation of UHF absorbers. Based on the enhanced channel model, a new method for tag readability prediction with high reliability has been introduced. Furthermore, a novel way to rate the magnitude of multipath interference has been proposed. A digital receiver beamforming localization method has been presented which uses the Root MUSIC algorithm for angulation of a target tag and multipath reducing techniques for an optimum localization performance. A new multiangulation algorithm has been proposed to enable the application of diversity techniques. A novel transmitter beamforming localization approach has been presented which exploits the precisely defined response threshold of passive tags in order to achieve high robustness against multipath. The basic technique has been improved significantly with respect to angular accuracy and processing times. Novel experimental testbeds for receiver and transmitter beamforming have been designed, built and used for verification of the localization performance in real-world measurements. All the improvements achieved contribute to an enhancement of the accuracy and especially the robustness of passive UHF RFID localization systems in multipath environments which is the main focus of this research.

New underwater passive sonar techniques are developed for enhancing target localization capabilities in shallow ocean environments. The ocean surface and the seabed act as acoustic mirrors that reflect sound created by boats or subsurface vehicles, which gives rise to echoes that can be heard by hydrophone receivers (underwater microphones). The goal of this work is to leverage this "multipath" phenomenon in new ways to determine the origin of the sound, and thus the location of the target. However, this is difficult for propeller driven vehicles because the noise they produce is both random and continuous in time, which complicates its measurement and analysis. Further, autonomous underwater vehicles (AUVs) pose additional challenges because very little is known about the sound they generate, and its similarity to that of boats. Existing methods for localizing propeller noise using multiple hydrophones have approached the problem either purely theoretically, or empirically such as by analyzing the interference patterns between multipath arrivals at different frequencies, however little has been published on building localization techniques that directly measure and utilize the time delays between multipath arrivals while simultaneously accounting for relevant environmental parameters. This research develops such techniques through a combination of array beamforming and advanced ray-based modeling that account for variations in bathymetry (seabed topography) as well as variations of the sound speed of the water. The basis for these advances come from several at-sea experiments in which different configurations of passive sonar systems recorded sounds emitted by different types of targets, including small boats and an autonomous underwater vehicle. Ultimately, these contributions may reduce the complexity and cost of passive systems that need to be deployed close to shore, such as for harbor security applications. Further, they also create new possibilities for applying passive sonar in remote ocean regions for tasks such as detecting illegal fishing activity. This dissertation makes three key contributions: 1. Analysis of the aspect-dependent acoustic radiation patterns of an underway autonomous underwater vehicle (AUV) through full-field wave modeling. 2. A two-hydrophone cross-correlation technique that leverages multipath as well as bathymetric variations to estimate the range and bearing of a small boat, supported by a mathematically rigorous performance analysis. 3. A multi-target localization technique based on directly measuring multipath from multiple small surface vessels using a small hydrophone array mounted to the nose of an AUV, which operates by cross-correlating two elevation beams on a single bearing.

En géophysique, les réseaux denses améliorent la caractérisation spatiale et fréquentielle des différents types d’ondes dans le milieu. Bien entendu, l’acquisition en surface est sujette aux ondes de surface qui sont très fortes. Les ondes de surface ont un fort impact sur les données géophysiques acquises au niveau du sol. Elles peuvent être considérées comme du bruit et être sujettes à la suppression puisqu’elles cachent l’information de sous-surface. Cependant, elles peuvent être utiles pour l’imagerie de proche surface si elles sont convenablement récupérées.Dans tous les cas, leur caractérisation est cruciale en géophysique d’exploration active et passive. Dans la surveillance microsismique passive, le bruit de surface ambiant est composé d’ondes de surface. L’objectif principal de la surveillance passive est de minimiser l’impact des ondes de surface sur les données microsismiques. Le fort bruit de surface diminue la sensibilité etl’efficacité des méthodes de détection et de localisation. De plus, les méthodes actuelles de localisation et de détection nécessitent généralement la connaissance d’informations telles qu’un un modèle de vitesse ou un modèle d’événement. Dans la sismique active, de fortes ondes de surface sont générés par des sources actives. Les stratégies actuelles de traitement sont généralement basées sur une sélection manuelle des ondes de surface afin de choisir lesquelles garder. Il s’agit là d’une tâche complexe, coûteuse et sujette à interprétation. Cependant, cette tâche est nécessaire pour l’imagerie de proche-surface et de sous-surface. Les ondes de surface peuvent être particulièrement difficiles à récupérer dans des acquisitions clairsemées.Nous proposons d’appliquer les techniques d’interférométrie et de formation de voies (telles que le Matched Field Processing) dans le contexte des réseaux denses. Une densité de traces importante ouvre de nouvelles possibilités dans les traitements géophysiques, qu’ils soient actifs ou passifs. Nous montrons que le bruit ambiant peut être utilisé dans le traitement microsismique pour extraire des informations importantes sur les propriétés du milieu. De plus, nous développons une approche de débruitage qui permet de supprimer les sources de bruit à la surface et détecter les événements microsismiques. Nous proposons également une méthode automatique de détection et de localisation qui se base sur une quantité minimale d’information préalable qui permet de récupérer la distribution des hétérogénéités du réservoir, dans le voisinage du puits. En ce qui concerne la sismique active, nous proposons une approche interférométrique et automatique de caractérisation des ondes de surface. Nous récupérons les noyaux de sensibilité de phase des ondes de surface entre deux points quelconques de l’acquisition. Ces noyaux de sensibilité sont par conséquent utilisés pour obtenir les courbes de dispersion multimodales. Ces courbes de dispersion permettent la séparation des différents modes des ondes de surface, et fournissent l’information de proche surface suite à une simple inversion.Le réseau dense permet l’amélioration des méthodes présentées ci-dessus: elle permet des applications alternatives et innovantes dans le traitement du signal géophysique
In geophysics, spatially dense arrays enhance the spatial and frequential characterization of the various waves propagating in the medium. Of course, surface array is subject to strong surface waves. Surface waves highly impact the processing of geophysical data acquired at ground level. They can be considered as noise and subject to suppression as they mask sub-surface information.However, they can be useful for near-surface imaging if they are well retrieved. In any case, their characterization is crucial in active and passive exploration geophysics. In passive microseismic monitoring, ambient surface noise consists of surface waves. The main goal of passive monitoring is to minimize the impact of surface waves on the actual microseismic data. The strong ambient surface noise lowers the sensitivity and the efficiency ofdetection and location methods. Moreover, current location and detection methods usually require strong a priori information (e.g., a velocity model or a template).Active sources generate strong surface waves. In active seismic, current processing strategies often consist in manually picking surface wave arrivals in order to use or remove them. This is often a complex, time consuming, and an ambiguous task. However, it is needed for near- and sub-surface imaging. Surface waves can be particularly difficult to retrieve in sparse arrays. We propose to apply the techniques of interferometry and beamforming (Matched Field Processing in particular) in the context of dense arrays. High trace density opens new possibilities in geophysical processing in both passive and active surveys. We show that the ambient noise can be explored in the case of microseismic monitoring to extract important information about the medium properties. Moreover, we develop a denoising approach to remove the noise sources at the surface and detect the microseismic event. Furthermore, we propose an automatic detection and location method with a minimum a priori information to retrieve the distribution of heterogeneities in the reservoir, in the well vicinity.In active survey, we propose an interferometric, automatic approach to characterize the surface waves. We retrieve phase-sensitivity kernels of surface waves between any two points of the acquisition. These kernels are consequently used to obtain multi-mode dispersion curves. These dispersion curves make it possible to separate different modes of surface waves and provide near-surface information if inverted.The above presented methodologies benefit from spatially dense arrays.Dense arrays of sources or receivers enable alternative, innovative applications in geophysical processing

As the need for more bandwidth increases, satellite communication (SatCom) terminals are forced to climb higher in frequency. Higher frequency means greater propagation losses, and so antenna gain and sensitivity have to increase. The higher the gain, the more difficult it is to point the antenna. To make matters even more challenging, consumers are requesting satellite links in harsher environments and on moving vehicle and planes. In order to meet today's challenges and improve on dish feeds, research is ongoing to replace fixed-beam feedhorns with smaller, cheaper, and lighter PCB based antennas and to develop low-cost electronically steered array feeds (ESAF). ESAFs will not only improve the signal link, but they will also aid in pointing the antenna and then tracking the satellite independent of movement. Here is presented some of the first planar antenna dish feeds developed by the Brigham Young University's SatCom Group. Included are the simulation and test procedures to determine if they are viable for SatCom use. The results show that these antennas make significant advancements in efficiencies and prove a path forward to a feedhorn replacement. Several planar designs are presented, each with a unique solution to meet all the requirements for a dish feed. Also presented is the first low-cost ESAFs developed to give commercial SatCom an electronically steerable dish. None of the designed hardware requires a redesign of current modems and receiver boxes. The research looks at keeping costs low by minimizing the required electronics. This further led to researching the limits on how simple the electronics could be. The ESAF doubled the visible area of the dish and successfully acquired and tracked a satellite as the dish moved. The ESAF also demonstrates a path forward to increase the steerable range and improve pointing and tracking.

Cette thèse est consacrée à l’exploitation des propriétés de non-circularité et de non-gaussianité des signaux d’intérêt (SOI) et/ou des interférences pour les transmissions sans fil et l’écoute passive. Dans une première partie de cette thèse, nous nous intéressons à l’extension des récepteurs SIMO-MLSE conventionnels vers de nouvelles architectures exploitant la potentielle non-circularité au second ordre des interférences co-canal (CCI), pour la démodulation de signaux rectilignes (BPSK, ASK), quasi-rectilignes (MSK, GMSK et OQAM) et à symboles complexes (QAM). L’architecture générale des récepteurs développés est basée sur un prétraitement avec une extension widely linear (WL) du filtre adapté spatio-temporel, ramenant le traitement de démodulation à un problème scalaire, un échantillonnage au rythme symbole et ensuite un organe de décision basé sur une version modifiée de l’algorithme de Viterbi. Pour le cas particulier des signaux quasi-rectiligne, on intercale un traitement de dérotation entre l’échantillonneur et l’organe de décision. Un travail de modélisation à temps discret des SOI, brouilleurs et du bruit de fond a été mené afin de créer des modèles de simulations pour la validation des expressions SINR analytiques interprétables, via l’évaluation des probabilités d’erreur symboles. Dans une deuxième partie, nous nous intéressons à la formation de voies (Beamforming) non-linéaire à travers des structures de Volterra complexe du troisième ordre. Ces dernières permettent l’exploitation de la non-circularité jusqu’au sixième ordre ainsi que du caractère non-gaussien des SOI et/ou des interférences. Dans le contexte de l’écoute passive, nous avons introduit un beamformer MVDR de Volterra du troisième ordre utilisant la seule information a priori du vecteur directionnel du SOI et implémentable grâce à une structure équivalente GSC. Nous avons étudié ses performances en particulier par l’évaluation analytique des expressions du SINR en fonction des statistiques de l’interférence, et par sa vitesse d’apprentissage, démontrant ainsi sa supériorité par rapport aux beamformers MVDR linéaire et WL classiques. Dans un contexte de radiocommunications, nous avons étudié une version MMSE de ce beamformer de Volterra complexe du troisième ordre qui prend lui en compte les propriétés statistiques de non-circularité jusqu’au sixième ordre et de non-gaussianité du SOI et du CCI. La dernière partie de cette thèse est consacrée à la robustesse de tests de détection de rectilinéarité de signaux en présente d’offsets de fréquence. Ces tests sont importants pour ajuster la nature du traitement (linéaire ou WL) en fonction de la rectilinéarité des signaux, afin de garantir le meilleur rapport performance/temps de convergence des algorithmes
This thesis is devoted to exploit the non-circularity and non-gaussianity properties of signals of interest (SOI) and/or interference for wireless transmissions and passive listening. In the first part of this thesis, we are interested in the extension of conventional SIMO-MLSE receivers to new architectures exploiting the potential second order non-circularity of co-channel interference (CCI), for the demodulation of rectilinear signals (BPSK, ASK), quasi-rectilinear (MSK, GMSK and OQAM) and quadrature amplitude modulation (QAM). The general architecture of the developed receivers is based on a pre-processing with a widely linear (WL) extension of the spatio-temporal matched filter, bringing the demodulation processing back to a scalar problem, a sampling at the symbol rate and then a decision block based on a modified version of the Viterbi algorithm. For the particular case of the quasi-rectilinear signals, a derotation processing is interposed between the sampler and the decision block. A work on equivalent discrete time modeling of SOI, interferers and background noise has been carried out in order to create simulation models as for the validation of the interpretable analytic SINR expressions, by the evaluation of the symbol error rates. In a second part, we are interested to the beamforming through complex Volterra structures of the third order. These structures allow us the exploitation of the non-circularity up to the sixth order as well as the non-gaussian nature of the SOI and/or the interferences. For passive listening applications, we have introduced a third-order Volterra MVDR beamformer using only a priori information of SOI steering vector and implemented by an equivalent GSC structure. We have studied its performance, in particular by interpretable closed-form expressions as functions of statistics of the interference, and by its speed of learning, thus proving its advantages with respect to the conventional linear and WL MVDR beamformers. For wireless communications applications, we have studied an MMSE version of this complex Volterra beamformer of the third order that takes into account of the non-circularity up to the sixth order as well as the non-gaussian nature of the SOI and interference. The last part of this thesis is devoted to the robustness of rectilinearity tests in the presence of frequency offset. These tests are important for adjusting the processing (linear or WL) as a function of the rectilinearity of the signals in order to guarantee the best performance/convergence rate ratio of algorithms

The work here presents a review of beam forming architectures. As an example, the author presents an 8x8 Butler Matrix passive beam forming network including the schematic, design/modeling, operation, and simulated results. The limiting factor in traditional beam formers has been the large size dictated by transmission line based couplers. By replacing these couplers with transformer-based couplers, the matrix size is reduced substantially allowing for on chip compact integration. In the example presented, the core area, including the antenna crossover, measures 0.82mm×0.39mm (0.48% the size of a branch line coupler at the same frequency). The simulated beam forming achieves a peak PNR of 17.1 dB and 15dB from 57 to 63GHz. At the 60GHz center frequency the average insertion loss is simulated to be 3.26dB. The 8x8 Butler Matrix feeds into an 8-element antenna array to show the array patterns with single beam and adjacent beam isolation.

Accurate modeling of acoustic propagation in the ocean waveguide is important to SONAR-performance prediction, and requires, particularly in shallow water environments, characterizing the bottom reflection loss with a precision that databank-based modeling cannot achieve. Recent advances in the technology of autonomous underwater vehicles (AUV) make it possible to envision a survey system for seabed characterization composed of a short array mounted on a small AUV. The bottom power reflection coefficient (and the related reflection loss) can be estimated passively by beamforming the naturally occurring marine ambient-noise acoustic field recorded by a vertical line array of hydrophones. However, the reduced array lengths required by small AUV deployment can hinder the process, due to the inherently poor angular resolution. In this dissertation, original data-processing techniques are presented which, by introducing into the processing chain knowledge derived from physics, can improve the performance of short arrays in this particular task. Particularly, the analysis of a model of the ambient-noise spatial coherence function leads to the development of a new proof of the result at the basis of the bottom reflection-loss estimation technique. The proof highlights some shortcomings inherent in the beamforming operation so far used in this technique. A different algorithm is then proposed, which removes the problem achieving improved performance. Furthermore, another technique is presented that uses data from higher frequencies to estimate the noise spatial coherence function at a lower frequency, for sensor spacing values beyond the physical length of the array. By "synthesizing" a longer array, the angular resolution of the bottom-loss estimate can be improved, often making use of data at frequencies above the array design frequency, otherwise not utilized for beamforming. The proposed algorithms are demonstrated both in simulation and on real data acquired during several experimental campaigns.

An aeroacoustic study was conducted on a 26%-scale Boeing 777 main landing gear in the Virginia Tech (VT) Anechoic Stability Wind Tunnel. The VT Anechoic Stability Wind Tunnel allowed noise measurements to be carried out using both a 63-elements microphone phased array and a linear array of 15 microphones. The noise sources were identified from the flyover view under various flow speeds and the phased array positioned in both the near and far-field. The directivity pattern of the landing gear was determined using the linear array of microphones. The effectiveness of 4 passive noise control devices was evaluated. The 26%-scale model tested was a faithful reproduction of the full-scale landing gear and included most of the full-scale details with accuracy down to 3 mm. The same landing gear model was previously tested in the original hard-walled configuration of the VT tunnel with the same phased array mounted on the wall of the test section, i.e. near-field position. Thus, the new anechoic configuration of the VT wind tunnel offered a unique opportunity to directly compare, using the same gear model and phased array instrumentation, data collected in hard-walled and semi-anechoic test sections. The main objectives of the present work were (i) to evaluate the validity of conducting aeroacoustic studies in non-acoustically treated, hard-walled wind tunnels, (ii) to test the effectiveness of various streamlining devices (passive noise control) at different flyover locations, and (iii) to assess if phased array measurements can be used to estimate noise reduction. As expected, the results from this work show that a reduction of the background noise (e.g. anechoic configuration) leads to significantly cleaner beamforming maps and allows one to locate noise sources that would not be identified otherwise. By using the integrated spectra for the baseline landing gear, it was found that in the hard-walled test section the levels of the landing gear noise were overestimated. Phased array measurements in the near and far-field positions were also compared in the anechoic configuration. The results showed that straight under the gear, near-field measurements located only the lower-truck noise sources, i.e. noise components located behind the truck were shielded. It was thus demonstrated that near-field, phased-array measurements of the landing gear noise straight under the gear are not suitable. The array was also placed in the far-field, on the rear-arc of the landing gear. From this position, other noise sources such as the strut could be identified. This result demonstrated that noise from the landing gear on the flyover path cannot be characterized by only taking phased array measurement right under the gear. The noise reduction potential of various streamlining devices was estimated from phased array measurements (by integrating the beamforming maps) and using the linear array of individually calibrated microphones. Comparison of the two approaches showed that the reductions estimated from the phased array and a single microphone were in good agreement in the far-field. However, it was found that in the near-field, straight under the gear, phased array measurements greatly overestimate the attenuation.
Master of Science

Cette thèse est consacrée à l’exploitation des propriétés de non-circularité et de non-gaussianité des signaux d’intérêt (SOI) et/ou des interférences pour les transmissions sans fil et l’écoute passive. Dans une première partie de cette thèse, nous nous intéressons à l’extension des récepteurs SIMO-MLSE conventionnels vers de nouvelles architectures exploitant la potentielle non-circularité au second ordre des interférences co-canal (CCI), pour la démodulation de signaux rectilignes (BPSK, ASK), quasi-rectilignes (MSK, GMSK et OQAM) et à symboles complexes (QAM). L’architecture générale des récepteurs développés est basée sur un prétraitement avec une extension widely linear (WL) du filtre adapté spatio-temporel, ramenant le traitement de démodulation à un problème scalaire, un échantillonnage au rythme symbole et ensuite un organe de décision basé sur une version modifiée de l’algorithme de Viterbi. Pour le cas particulier des signaux quasi-rectiligne, on intercale un traitement de dérotation entre l’échantillonneur et l’organe de décision. Un travail de modélisation à temps discret des SOI, brouilleurs et du bruit de fond a été mené afin de créer des modèles de simulations pour la validation des expressions SINR analytiques interprétables, via l’évaluation des probabilités d’erreur symboles. Dans une deuxième partie, nous nous intéressons à la formation de voies (Beamforming) non-linéaire à travers des structures de Volterra complexe du troisième ordre. Ces dernières permettent l’exploitation de la non-circularité jusqu’au sixième ordre ainsi que du caractère non-gaussien des SOI et/ou des interférences. Dans le contexte de l’écoute passive, nous avons introduit un beamformer MVDR de Volterra du troisième ordre utilisant la seule information a priori du vecteur directionnel du SOI et implémentable grâce à une structure équivalente GSC. Nous avons étudié ses performances en particulier par l’évaluation analytique des expressions du SINR en fonction des statistiques de l’interférence, et par sa vitesse d’apprentissage, démontrant ainsi sa supériorité par rapport aux beamformers MVDR linéaire et WL classiques. Dans un contexte de radiocommunications, nous avons étudié une version MMSE de ce beamformer de Volterra complexe du troisième ordre qui prend lui en compte les propriétés statistiques de non-circularité jusqu’au sixième ordre et de non-gaussianité du SOI et du CCI. La dernière partie de cette thèse est consacrée à la robustesse de tests de détection de rectilinéarité de signaux en présente d’offsets de fréquence. Ces tests sont importants pour ajuster la nature du traitement (linéaire ou WL) en fonction de la rectilinéarité des signaux, afin de garantir le meilleur rapport performance/temps de convergence des algorithmes
This thesis is devoted to exploit the non-circularity and non-gaussianity properties of signals of interest (SOI) and/or interference for wireless transmissions and passive listening. In the first part of this thesis, we are interested in the extension of conventional SIMO-MLSE receivers to new architectures exploiting the potential second order non-circularity of co-channel interference (CCI), for the demodulation of rectilinear signals (BPSK, ASK), quasi-rectilinear (MSK, GMSK and OQAM) and quadrature amplitude modulation (QAM). The general architecture of the developed receivers is based on a pre-processing with a widely linear (WL) extension of the spatio-temporal matched filter, bringing the demodulation processing back to a scalar problem, a sampling at the symbol rate and then a decision block based on a modified version of the Viterbi algorithm. For the particular case of the quasi-rectilinear signals, a derotation processing is interposed between the sampler and the decision block. A work on equivalent discrete time modeling of SOI, interferers and background noise has been carried out in order to create simulation models as for the validation of the interpretable analytic SINR expressions, by the evaluation of the symbol error rates. In a second part, we are interested to the beamforming through complex Volterra structures of the third order. These structures allow us the exploitation of the non-circularity up to the sixth order as well as the non-gaussian nature of the SOI and/or the interferences. For passive listening applications, we have introduced a third-order Volterra MVDR beamformer using only a priori information of SOI steering vector and implemented by an equivalent GSC structure. We have studied its performance, in particular by interpretable closed-form expressions as functions of statistics of the interference, and by its speed of learning, thus proving its advantages with respect to the conventional linear and WL MVDR beamformers. For wireless communications applications, we have studied an MMSE version of this complex Volterra beamformer of the third order that takes into account of the non-circularity up to the sixth order as well as the non-gaussian nature of the SOI and interference. The last part of this thesis is devoted to the robustness of rectilinearity tests in the presence of frequency offset. These tests are important for adjusting the processing (linear or WL) as a function of the rectilinearity of the signals in order to guarantee the best performance/convergence rate ratio of algorithms

La récupération d’énergie électromagnétique provenant de sources ambiantes ou intentionnelles, de fréquences allant de 100 MHz à 10 GHz, est apparue ces dernières années comme une solution prometteuse pour développer l’électronique autoalimentée. Cependant, les faibles densités de puissance, généralement plus faibles que 1 μW.cm-2, engendrent de faibles efficacités de redressement et de faibles sensibilités, et la diversité des signaux ambients (direction d’arrivée et polarisation inconnues et variant dans le temps) ne permet pas d’utiliser des antennes directives.Dans cette thèse, les techniques de combinaison de la puissance RF ou DC dans des systèmes de récupération d’énergie à multiples antennes, associées à des structures originales, sont étudiées pour faire face aux différents verrous technologiques. De plus, une nouvelle Figure-de-Mérite, décrivant la capacité d’un système à récupérer de l’énergie ambiante, est développée avec des termes de probabilités représentant la diversité fréquentielle, spatiale et de polarisation des signaux ambiants.La première partie de cette thèse se consacre à la conception d’antennes et de rectennas individuelles efficaces. Des prototypes peu chers et recyclables sont proposés sur un substrat papier grâce à une technique originale de réduction des pertes.Dans la deuxième partie de cette thèse, l’efficacité de conversion RF-DC est améliorée à travers la combinaison de la puissance RF avant le processus de redressement, sans pour autant réduire la couverture spatiale du système. Pour cela, une structure 3D multidirectionnelle de réseaux d’antennes associés à des réseaux interférométriques passifs, pour la formation de faisceaux, est conçue, afin d’obtenir un diagramme de rayonnement multidirectionnel à fort gain. Cette solution inspirée des systèmes de radar et impliquant des matrices de Butler, aboutit à une haute efficacité de conversion RF-DC ainsi qu’à une couverture spatiale optimale. Ainsi, une capacité à récupérer de l’énergie plus grande que celles de l’état-de-l’art est obtenue.La dernière partie de cette thèse propose de remédier à la limite en sensibilité de la combinaison de puissance RF, plus faible qu’avec une combinaison DC en série de la puissance, grâce à un système reconfigurable. Pour cela, des cellules unitaires de rectennas sont conçues afin de former un réseau interférométrique adaptable et extensible, qui offre la possibilité d’obtenir un système hautement efficace et sensible à la fois. Cette solution peut servir à la récupération d’énergie, à la localisation passive et autonome ou à des applications RFID
Wireless energy harvesting (WEH) of ambient or intentional electromagnetic power sources of frequency ranging from 100 MHz to 10 GHz, has appeared as a promising solution to develop self-powered electronics in the past decades. However, the low power densities available, usually lower than 1 uW.cm-2, result in a limited RF-to-DC conversion efficiency and sensitivity of the energy harvesting system (rectenna) and the ambient signal diversities (unknown and time-varying direction of arrival, polarization) prohibit the use of directive antennas.In this thesis, the power combination techniques of Radio Frequency (RF) or Direct Current (DC) power in multi-antenna WEH systems, together with original structures, are investigated to address those challenges. Besides, a new Figure-of-Merit (harvesting capability) for rectennas operating in ambient scenarios is derived with probabilistic terms representing the frequency, polarization and spatial diversities of ambient signals.The first part of this thesis focuses on the design of efficient antenna and rectenna elements. Eco-responsible and low-cost prototypes are proposed by using a paper substrate along with an original strategy for the reduction of the losses.In the second part of this work, the rectification efficiency of a WEH system is enhanced through the combination of the RF power prior to the rectification process, without reduction of the spatial coverage. For this, a 3D multidirectional structure of scanning antenna arrays using passive beam-forming networks is designed to obtain a multidirectional high gain aggregate pattern. This radar-inspired solution involving Butler matrices results in a highly efficient RF-to-DC power conversion along with an optimal angular coverage, which leads to a harvesting capability higher than the state-of-the-art.The last part of this work addresses the limited sensitivity of the RF combination technique compared to that obtained with the series DC combination technique thanks to a reconfigurable system. To this end, modular rectenna unit cells are designed to form a scalable and adaptative interferometric beam-forming network, which offers the possibility to achieve a highly efficient and sensitive WEH system. This solution is suitable for low-power energy harvesting, autonomous passive tracking or RFID applications

This thesis contains design of beamforming network designed for passive radar antennas. The first part contains theory of passive radars and beamforming networks. The next part implies design of beamforming network at the block digram level. Then are choosed circuits for amplitude and phase control, including the design of control communication. It follows by realization of IQ phase shifter and his automatic measurement. Based on this results is phase shifter adjusted and PCB of 2x2 beamforming network is designed. Last part includes design of control application (Matlab) and control program for STM32F407VG microcontroller.

L'évolution technologique rapide introduite par les générations des communications sans fil a été motivé par l'émergence de services à fortes valeurs ajoutées nécessitant toujours plus de débit mais aussi une couverture bien meilleure, ceci conduisant in fine à utiliser le spectre plus efficacement. Pour ce faire, la Sixième Génération (6G) des réseaux sans fil, pourra s'appuyer sur des technologies innovantes telles que les Surfaces Intelligentes Reconfigurables (RIS) et le Massive Multiple Input Multiple Output (mMIMO), ces dernières pourraient y jouer des rôles cruciaux. Cette thèse explore l'intégration des RIS dans les systèmes mMIMO dans le but d'améliorer les performances des communications sans fil.La première partie de la thèse, porte sur l'application de la Division et Multiplexage Spatiaux Conjoint (JSDM) dans les systèmes MIMO multi-utilisateur assistés par une RIS. En positionnant stratégiquement les RIS près des utilisateurs dont les canaux directs avec la station de base (BS) sont dégradés, nous développons des solutions pour adapter les algorithmes de regroupement d'utilisateurs JSDM en prenant en compte les configurations RIS. Cette approche exploite les signatures spatiales et introduit une étape de précodage supplémentaire pour le JSDM, atténuant les effets néfastes du canal RIS-BS, améliorant ainsi significativement le débit somme et la couverture du système. Les solutions proposées démontrent le potentiel des RIS dans le but d'améliorer la couverture en établissant des liens robustes entre la BS et les utilisateurs, améliorant ainsi les performances globales du réseau.La deuxième partie aborde le défi des canaux BS-RIS de faible rang en proposant un système RIS distribué. En déployant des RIS intermédiaires entre la BS et une RIS principale, nous créons un canal intégré ayant un rang amélioré, et adapté pour servir plusieurs utilisateurs simultanément. La performance de ce paradigme est évaluée en prenant un précodage Regularized Zero Forcing (RZF) et le JSDM,les décalages de phase des signaux, par les RISs, y sont optimisés par un algorithme de montée de gradient projeté. Les résultats démontrent des améliorations de performance substantielles, même dans des conditions de perte de chemin élevée, due à la double réflexion par les RISs. Cette stratégie de déploiement augmente non seulement le gain de multiplexage spatial, mais aussi réduit la complexité de l'estimation de l'information sur l'état du canal.Dans la dernière partie, nous introduisons un nouveau cadre coopératif qui permet aux RIS de changer dynamiquement de rôle entre principal et intermédiaire. Cette double fonctionnalité permet des réponses flexibles d'une part aux évolutions environnementales et d'autre part aux besoins des utilisateurs, en optimisant dynamiquement les gains de multiplexage spatial ainsi que la couverture. La conception d'un codebook de focalisation pour chaque RIS et la mise en place de la politique de planification dynamique basées sur la théorie de l'optimisation de Lyapunov permettre de maintenir la stabilité des files d'attente de données des utilisateurs et d'optimiser les débits à long terme. La planification coopérative garantit que le gain de multiplexage spatial est dynamiquement transféré d'une région à une autre, offrant des performances MU-MIMO fiables tout au long de la cellule.À travers des études analytiques et de simulation rigoureuses, cette thèse fournit des perspectives pratiques sur le déploiement des RIS, soulignant le potentiel de la technologie RIS dans le but d'améliorer significativement les performances de communication sans fil. Les résultats soulignent l'impact important des RIS sur l'efficacité du réseau, la couverture et l'expérience utilisateur, ouvrant la voie à la prochaine génération de systèmes de communication sans fil
The rapid advancement of wireless communication technologies has been driven by the increasing demand for higher data rates, better coverage, and more efficient spectrum utilization. As we transition towards the Sixth Generation (6G) of wireless networks, innovative technologies such as Reconfigurable Intelligent Surfaces (RIS) and Massive MIMO (mMIMO) are set to play crucial roles in meeting these demands. This thesis explores the integration of RIS with mMIMO systems to enhance wireless communication performance, particularly in Multi-User MIMO (MU-MIMO) scenarios.In the first part of the thesis, we focus on the application of Joint Spatial Division and Multiplexing (JSDM) in RIS-aided MU-MIMO systems. By strategically positioning RIS near users with weak direct Base Station (BS) channels, we develop solutions to adapt JSDM user clustering algorithms for RIS configurations. This approach leverages spatial signatures and introduces an additional precoding stage to JSDM mitigating the adverse effects of the RIS-BS channel, significantly improving the sum rate and system coverage. The proposed solutions demonstrate the potential of RIS to enhance coverage by establishing robust links between the BS and users, thereby improving overall network performance.The second part of the thesis addresses the challenge of low-rank BS-RIS channels by proposing a distributed RIS system. By deploying intermediate RISs between the BS and a main RIS, we create an integrated channel with enhanced rank characteristics, suitable for serving multiple users simultaneously. The performance of this paradigm is analyzed under Regularized Zero Forcing (RZF) and JSDM precoding, with RIS phase shifts optimized through a projected gradient ascent algorithm. The results demonstrate substantial performance improvements, even under high double reflection path-loss conditions. This innovative deployment strategy not only increases the spatial multiplexing gain but also reduces the complexity of channel state information (CSI) estimation.In the final part, we introduce a novel cooperative RIS framework that allows RISs to dynamically switch roles between main and intermediate. This dual functionality enables flexible responses to changing environmental conditions and user requirements, optimizing spatial multiplexing gains and overall coverage. We design a focusing codebook for each RIS and develop dynamic scheduling policies based on Lyapunov optimization theory to maintain user data queue stability and optimize long-term user data rates. The cooperative scheduling framework ensures that the spatial multiplexing gain is dynamically shifted from one region to another, providing reliable MU-MIMO performance throughout the cell.Through rigorous analytical and simulation studies, this thesis provides practical insights into the deployment of RIS in future 6G networks, highlighting the potential of RIS technology to significantly enhance wireless communication performance. The findings underscore the transformative impact of RIS on network efficiency, coverage, and user experience, paving the way for the next generation of wireless communication systems

This dissertation proposes an iterative confidence passing (ICP) approach for parameter estimation. The dissertation describes three different algorithms that follow from this ICP approach. These three variations of the ICP approach are applied to (a) macrodiversity and user cooperation diversity reception problems, (b) the co-operative multipoint MIMO reception problem (pertinent to the LTE Advanced system scenarios), and (c) the satellite beamforming problem. The first two of these three applications are some of the significant open DSP research problems that are currently being actively pursued in academia and industry. This dissertation demonstrates a significant performance improvement that the proposed ICP approach delivers compared to the existing known techniques. The proposed ICP approach jointly estimates (and, thereby, separates) two sets of unknown parameters from the receiver measurements. For applications (a) and (b) mentioned above, one set of unknowns is comprised of the discrete-valued information-bearing transmitted symbols in a multi-channel communication system, and the other set of unknown parameters is formed by the coefficients of a Rayleigh or Rician fading channel. Application (a) is for interference-free, cooperative or macro, transmit or receive, diversity scenarios. Application (b) is for MIMO systems with interference-rich reception. Finally, application (c) is for an interference-free spacecraft array calibration system model in which both the sets of unknowns are complex continuous valued variables whose magnitude follows the Rician distribution. The algorithm described here is the outcome of an investigation for solving a difficult channel estimation problem. The difficulty of the estimation problem arises because (i) the channel of interest is intermittently observed, and (ii) the partially observed information is not directly of the channel of interest; it has dependency on another unknown and uncorrelated set of complex-valued random variables. The proposed ICP algorithmic approach for solving the above estimation problems is based on an iterative application of the Weighted Least Squares (WLS) method. The main novelty of the proposed algorithm is a back and forth exchange of the confidence or the belief values in the WLS estimates of the unknown parameters during the algorithm iterations. The confidence values of the previously obtained estimates are used to derive the estimation weights at the next iteration, which generates an improved estimate with a greater confidence. This method of iterative confidence (or belief) passing causes a bootstrapping convergence to the parameter estimates. Besides the ICP approach, several alternatives are considered to solve the above problems (a, b and c). Results of the performance simulation of the alternative methods show that the ICP algorithm outperforms all the other candidate approaches. Performance benefit is significant when the measurements (and the initial seed estimates) have non-uniform quality, e.g., when many of the measurements are either non-usable (e.g., due to shadowing or blockage) or are missing (e.g., due to instrument failures).
Ph. D.

Des antennes multiples du côté de la station de base peuvent être utilisées pour améliorer l'efficacité spectrale et l'efficacité énergétique des technologies sans fil de nouvelle génération. En effet, le multi-entrées et sorties multiples massives (MIMO) est considéré comme une technologie prometteuse pour apporter les avantages susmentionnés pour la norme sans fil de cinquième génération, communément appelée 5G New Radio (5G NR). Dans cette monographie, nous explorerons un large éventail de sujets potentiels dans Multi-userMIMO (MU-MIMO) pertinents pour la 5G NR,• Conception de la formation de faisceaux (BF) maximisant le taux de somme et robustesse à l'état de canal partiel informations à l'émetteur (CSIT)• Analyse asymptotique des différentes techniques BF en MIMO massif et• Méthodes d'estimation de canal bayésien utilisant un apprentissage bayésien clairsemé.L'une des techniques potentielles proposées dans la littérature pour contourner la complexité matérielle et la consommation d'énergie dans le MIMO massif est la formation de faisceaux hybrides. Nous proposons une conception de phaseur analogique globalement optimale utilisant la technique du recuit déterministe, qui nous a valu le prix du meilleur article étudiant. En outre, afin d'analyser le comportement des grands systèmes des systèmes MIMO massifs, nous avons utilisé des techniques de la théorie des matrices aléatoires et obtenu des expressions de taux de somme simplifiées. Enfin, nous avons également examiné le problème de récupération de signal bayésien clairsemé en utilisant la technique appelée apprentissage bayésien clairsemé (SBL)
Multiple antennas at the base station side can be used to enhance the spectral efficiency and energy efficiency of the next generation wireless technologies. Indeed, massive multi-input multi-output (MIMO) is seen as one promising technology to bring the aforementioned benefits for fifth generation wireless standard, commonly known as 5G New Radio (5G NR). In this monograph, we will explore a wide range of potential topics in multi-userMIMO (MU-MIMO) relevant to 5G NR,• Sum rate maximizing beamforming (BF) design and robustness to partial channel stateinformation at the transmitter (CSIT)• Asymptotic analysis of the various BF techniques in massive MIMO and• Bayesian channel estimation methods using sparse Bayesian learning.One of the potential techniques proposed in the literature to circumvent the hardware complexity and power consumption in massive MIMO is hybrid beamforming. We propose a globally optimal analog phasor design using the technique of deterministic annealing, which won us the best student paper award. Further, in order to analyze the large system behaviour of the massive MIMO systems, we utilized techniques from random matrix theory and obtained simplified sum rate expressions. Finally, we also looked at Bayesian sparse signal recovery problem using the technique called sparse Bayesian learning (SBL). We proposed low complexity SBL algorithms using a combination of approximate inference techniques such as belief propagation (BP), expectation propagation and mean field (MF) variational Bayes. We proposed an optimal partitioning of the different parameters (in the factor graph) into either MF or BP nodes based on Fisher information matrix analysis

Le bruit rayonné par le trafic maritime étant la principale source de nuisance acoustique sous-marine dans les zones littorales, la Directive-Cadre Stratégie pour le Milieu Marin de la Commission Européenne promeut le développement de méthodes de surveillance et de réduction de l'impact du bruit du trafic maritime. Le besoin de disposer d'un système industriel d'imagerie du bruit rayonné par les navires de surface a motivé la présente étude, il permettra aux industriels du naval d'identifier quels éléments d'un navire rayonnent le plus de bruit.Dans ce contexte, ce travail de recherche porte sur la mise en place de méthodes d'imagerie acoustique sous-marine passive d'un navire de surface au passage au-dessus d'une antenne linéaire et fixe au nombre réduit d'hydrophones. Deux aspects de l'imagerie acoustique sont abordés : la localisation de sources acoustiques et l'identification de la contribution relative de chacune de ces sources dans la signature acoustique du navire.Tout d'abord, une étude bibliographique sur le rayonnement acoustique d'un navire de surface au passage est menée afin d'identifier les principales sources acoustiques et de pouvoir ensuite simuler des sources représentatives d'un navire. La propagation acoustique est simulée par la théorie des rayons et intègre le mouvement des sources. Ce simulateur de rayonnement acoustique de navire au passage est construit afin de valider les algorithmes d'imagerie acoustique proposés et de dimensionner une configuration expérimentale. Une étude sur l'influence du mouvement des sources sur les algorithmes d'imagerie acoustique a conduit à l'utilisation d'un algorithme de formation de voies pour sources mobiles pour la localisation des sources et une méthode de déconvolution pour accéder à l'identification de la contribution des sources. Les performances de ces deux méthodes sont évaluées en présence de bruit de mesure et d'incertitudes sur le modèle de propagation afin d'en connaître les limites. Une première amélioration de la méthode de formation de voies consiste en un traitement d'antenne à ouverture synthétique qui exploite le mouvement relatif entre le navire et l'antenne pour notamment améliorer la résolution en basses fréquences. Un traitement de correction acoustique de la trajectoire permet de corriger la trajectographie du navire au passage qui est souvent incertaine. Enfin, la dernière partie de cette thèse concerne une campagne de mesures de bruit de passage d'une maquette de navire de surface tractée en lac, ces mesures ont permis de valider les méthodes d'imagerie acoustique proposées ainsi que les améliorations proposées, dans un environnement réel maîtrisé
Since the surface ship radiated noise is the main contribution to the underwater acoustic noise in coastal waters, The Marine Framework Strategy Directive of the European Commission recommends the development of the monitoring and the reduction of the impact of the traffic noise. The need for developing an industrial system for the noise mapping of the surface ship have motivated this study, it will allow the naval industries to identify which part of the ship radiates the stronger noise level.In this context, this research work deals with the development of passive noise mapping methods of a surface ship passing-by above a static linear array with a reduced number of hydrophones. Two aspects of the noise mapping are considered: the localization of acoustic sources and the identification of the relative contribution of each source to the ship acoustic signature.First, a bibliographical study concerning the acoustic radiation of a passing-by surface ship is conducted in order to list the main acoustic sources and then to simulate representative ship sources. The acoustic propagation is simulated according to the ray theory and takes the source motion into account. The simulator of the acoustic radiation of a passing-by ship is built in order to validate the proposed noise mapping methods and to design an experimental set-up. A study about the influence of the source motion on the noise mapping methods led to the use of the beamforming method for moving sources for the source localization and a deconvolution method for the identification of the source contribution. The performances of both methods are assessed considering measurement noise and uncertainties about the propagation model in order to know their limitations. A first improvement of the beamforming method consists of a passive synthetic aperture array algorithm which benefits from the relative motion between the ship and the antenna in order to improve the spatial resolution at low frequencies. Then, an algorithm is proposed to acoustically correct the trajectography mismatches of a passing-by surface ship. Finally, the last part of this thesis concerns a pass-by experiment of a towed-ship model in a lake. These measurements allowed us to validate the proposed noise mapping methods and their proposed improvements, in a real and controlled environment

碩士
元智大學
通訊工程學系
98
The purpose of the thesis is to design an advanced adaptive array beamforming algorithm, which can be applied to future passive radar systems. First, the transmitted signal is lent from the FM radio stations, since the passive radar doesn’t emit any signal, it has the stealth advantage and wouldn’t be attacked by enemy. At the receiver, we use the smart antenna beamforming technology to suppress the directional interference signals. Next, using the reference signal received from reference antenna can eliminate the direct path interference. Then, we use the adaptive algorithms to achieve interference suppression, e.g., Least Mean Square (LMS) and Recursive Least Square (RLS) algorithms. Moreover, we develop the Linear-Constraint (LC) LMS algorithm to enhance the convergence speed and performance of the adaptive filtering. Besides, we also propose the space-time signal processor to increase the degrees of freedom, suppress more interferences, and improve the system performance. Finally, we study the angle mismatch problem and propose the multiple-constraint technique to overcome the degradation of the interference suppression. The proposed system is simulated and analyzed in terms of the output-SINR performance under the Gaussian noise and multipath fading channels environment. The performance results are confirmed to meet the requirements of the future passive radar systems.

The topic of multiple input multiple output (MIMO) radar recently gained considerable interest because it can transmit partially correlated or fully independent waveforms. The inherited waveform diversity helps MIMO radars identify more targets and adds flexibility to the beampattern design. The realized advantages come at the expense of enhanced processing requirements and increased system complexity. In this regards, a closed-form method is derived to generate practical finite-alphabet waveforms with specific correlation properties to match the desired beampattern. Next, the performance of adaptive estimation techniques is examined. Indeed, target localization or reflection coefficient estimation usually involves optimizing a given cost-function over a grid of points. The estimation performance is directly affected by the grid resolution. In this work, the cost function of Capon and amplitude and phase estimation (APES) adaptive beamformers are reformulated. The new cost functions can be evaluated using the two-dimensional fast-Fourier-transform (2D-FFT) which reduces the estimation runtime. Generalized expressions of the Cram´er-Rao lower bound are computed to assess the performance of our estimators. Afterward, a novel estimation algorithm based on the monopulse technique is proposed. In comparison with adaptive methods, monopulse requires less number of received pulses. Hence, it is widely used for fast target localization and tracking purposes. This work suggests an approach that localizes two point targets present in the hemisphere using one set of four antennas. To separate targets sharing the same elevation or azimuth angles, a second set of antennas is required. Two solutions are suggested to combine the outputs from the antenna sets and improve the overall detection performance. The last part of the dissertation focuses on the application and implementation side of radars rather than the theoretical aspects. It describes the realized hardware and software design of a compact portable 24 GHz frequency-modulated-continuous-wave (FMCW) radar. The prototype can assist the visually impaired during their outdoor journeys and prevents collisions with their surrounding environment. Moreover, the device performs diverse tasks such as range-direction mapping, velocity estimation, presence detection, and vital sign monitoring. The experimental result section demonstrates the device’s capabilities in different use-cases.