Les cyclones tropicaux, gigantesques machines thermiques redistribuent l'énergie entre les régions chaude et froide du globe. Cette énergie (chaleur latente) provient surtout des processus de condensation. La connaissance de la chaleur latente devrait améliorer la prévision de l'évolution de ses systèmes dévastateurs détectables par satellite. TRMM lancé en 1997, permet la restitution des contenus en hydrométéores grâce à des mesures couplées radar/radiomètre (PR/TMI). Cette thèse porte sur la restitution de la chaleur latente. On a donc développé un algorithme original de type bayésien utilisant des bases de données, construites à partir des mesures du PR. Cette méthode, appliquée au cyclone Bret (1999) a été validée par comparaison avec des résultats de mesures aéroportées et sol. On reproduit assez bien sur ce cas une structure énergétique propre à différents stade de son évolution. Une étude statistique pourrait ainsi permettre un diagnostic de l'évolution.

Réduire la vulnérabilité et accroître la résilience des sociétés d'aujourd'hui aux fortes précipitations et inondations exige de mieux caractériser leur très forte variabilité spatio-temporelle observable sur une grande gamme d'échelle. Nous mettons donc en valeur tout au long de cette thèse l'intérêt méthodologique d'une approche multifractale comme étant la plus appropriée pour analyser et simuler cette variabilité. Cette thèse aborde tout d'abord le problème de la qualité des données, qui dépend étroitement de la résolution temporelle effective de la mesure, et son influence sur l'analyse multifractale et la détermination de lois d'échelle des processus de précipitations. Nous en soulignons les conséquences pour l'hydrologie opérationnelle. Nous présentons la procédure SERQUAL qui permet de quantifier cette qualité et de sélectionner les périodes correspondant aux critères de qualité requise. Un résultat surprenant est que les longues chronologies de pluie ont souvent une résolution effective horaire et rarement de 5 minutes comme annoncée. Ensuite, cette thèse se penche sur les données sélectionnées pour caractériser la structure temporelle et le comportement extrême de la pluie. Nous analysons les sources d'incertitudes dans les méthodes multifractales " classiques " d'estimation des paramètres et nous en déduisons des améliorations pour tenir compte, par exemple, de la taille finie des échantillons et des limites de la dynamique des capteurs. Ces améliorations sont utilisées pour obtenir les caractéristiques multifractales de la pluie à haute résolution de 5 minutes pour plusieurs départements de la France (à savoir, les départements 38, 78, 83 et 94) et pour aborder la question de l'évolution des précipitations durant les dernières décennies dans le cadre du changement climatique. Cette étude est confortée par l'analyse de mosaïques radars concernant trois événements majeurs en région parisienne. Enfin, cette thèse met en évidence une autre application des méthodes développées, à savoir l'hydrologie karstique. Nous discutons des caractéristiques multifractales des processus de précipitation et de débit à différentes résolutions dans deux bassins versant karstiques au sud de la France. Nous analysons, en utilisant les mesures journalière, 30 minutes et 3 minutes, la relation pluie-débit dans le cadre multifractal. Ceci est une étape majeure dans la direction d'une définition d'un modèle multi-échelle pluie-débit du fonctionnement des bassins versants karstiques

This thesis addresses the design study, implementation and analysis of signal processing algorithms for a 79 GHz millimeter-wave Phase Modulated Continuous Wave (PMCW) Multi Input Multi Output (MIMO) short range radar; performed in IMEC research institute (Leuven, Belgium). The radar system targets high resolution performance with low power consumption in order to integrate a full MIMO radar transceiver with digital processor and antennas in a compact package featuring a size of 1 cm2. Achieving such radar system characteristics requires the exploitation of a highly demanding digital architecture with signal processing gain and high range, speed and angle resolutions. The improved resolution and detection capabilities will be achieved by performing signal processing algorithms on the reflected waveform. The digital front-end implements parallel range gate processing with a bank of correlators that perform: pulse compression, coherent accumulation to further increase Signal to Noise Ratio (SNR) and N-point FFT to extract the Doppler information. The use of MIMO is proposed implementing a code domain technique in the PMCW waveform, the Outer Hadamard Code MIMO. This concept makes use of a unique sequence for all the transmitting antennas that is rendered by an outer sequence to ensure the orthogonality of the transmitted waveforms. The outer code makes use of the good cross-correlation properties of the Hadamard sequences and the waveform uses sequences that exhibit perfect auto-correlation profile, the Almost Perfect Autocorrelation Sequences (APAS). The MIMO implementation results in higher angular resolution and extra processing gain. The use of beamforming techniques in the radar allows the angle estimation of the detected targets; using rough and fine beamforming that provides with coarse and precise Angle of Arrival (AoA) estimation in an early and late stage respectively. A Constant False Alarm Rate (CFAR) processing stage is implemented in the stage of the system where higher signal processing gain is achieved. This algorithm allows the variation of the CFAR parameters and analyzes the detections in order to improve the probability of detection (Pd) while decreasing the probability of false alarm (Pfa). A series of simulations with different scenarios and variable parameters are set in order to analyze the performance of the system. The simulations analyze the gain achieved in each stage and their outcomes show an impressive processing gain that can reach SNR improvements as high as 77 dB for a small virtual array while keeping the Pfa low with the CFAR adjustment. The use of bigger arrays demonstrates the possibility to enable clear detections for low Radar Cross Section (RCS) targets in far distances of the unambiguous range. The use of beamforming shows interference reduction improvement as the beam widths narrow with the increasing number of virtual array antennas. These results have been achieved while keeping the system design parameters to a range resolution of 7.5 cm for a maximum range of 37.5 meters with speed resolution of 0.2 m/s and a maximum detectable speed of 12.66 m/s. The outcomes support the good performance of the signal processing techniques implemented and the benefits in applying them in a SoC mmWave MIMO radar.

Στην εργασία αυτή, μελετάται το πρόβλημα της ανίχνευσης κινούμενων στόχων και της εκτίμησης της θέσης και της ταχύτητάς τους από ένα σύστημα ραντάρ. Η κίνηση των στόχων ως προς το ραντάρ έχει σαν αποτέλεσμα τη μετατόπιση Doppler της συχνότητας της επιστρεφόμενης ακτινοβολίας ως προς τη συχνότητα εκπομπής του ραντάρ. Εκτιμώντας αυτή τη μετατόπιση στη συχνότητα μπορούμε να ανιχνεύσουμε το στόχο καθώς και να εκτιμήσουμε τη θέση και την ταχύτητά του. Διερευνάται η δυνατότητα βελτίωσης της πιθανότητας ανίχνευσης των στόχων καθώς και του μέσου τετραγωνικού σφάλματος των εκτιμήσεων θέσης και ταχύτητας, με χρήση μοντέρνων εκτιμητών συχνοτήτων, αντί των κλασσικών εκτιμητών που βασίζονται στο Μετασχηματισμό Fourrier. Αναλύονται θεωρητικά και μέσω προσομοιώσεων οι δυνατότητες των μοντέρνων εκτιμητών συχνοτήτων, δίνοντας ιδιαίτερη έμφαση στους εκτιμητές Υποχώρου (MUSIC, ESPRIT). Ακολουθεί, η παρουσίαση μιας γενίκευσης της χρήσης των εκτιμητών συχνοτήτων στην περίπτωση διανυσματικών σημάτων. Ο αλγόριθμος που προτείνεται για την ανίχνευση στόχων από ένα σύστημα ραντάρ, επεξεργάζεται τα δείγματα της ληφθείσας ακτινοβολίας κατά μπλοκ οπότε προκύπτει η ανάγκη χρήσης αυτής της διανυσματικής μορφής των εκτιμητών συχνοτήτων. Παρουσιάζονται, τέλος, αποτελέσματα προσομοιώσεων, για διάφορα σενάρια, που επιβεβαιώνουν την αποτελεσματικότητα του αλγορίθμου και φανερώνουν τα πλεονεκτήματα της χρήσης των μοντέρνων τεχνικών εκτίμησης συχνοτήτων. / This report focuses on the problem of detection of moving targets and estimation of their positions and velocities using a radar system. By estimating the targets' Doppler frequencies it is possible to detect the targets and estimate both their position and velocity. It is shown how the use of modern frequency estimators results in higher values of the probability of detection compared to the Fourrier-based methods. Modern estimators are analyzed, with emphasis shown on the subspace-based estimators (MUSIC, ESPRIT) and their use is generalized for the case of estimating frequencies in vector signals. This generalized form of frequency estimators is used by our proposed algorithm for target detection. Simulation results are presented that prove the superiority of modern techniques.

It is proven that the ongoing refinement of the quality of rainfall data hand in hand with time and space variability of the rainfall has immense effect on the management of watercourses, flood control and hydrologic modelling. The aim of this thesis is to do an analysis of selected precipitation events in the Kopaninský stream research basin for more accurate information on rainfall-runoff processes. The aim of the analysis of individual precipitation events is to evaluate differences in total precipitation and volume measurements recorded in the basin and radar estimated precipitation. The output is detailed data series of spatial and temporal distribution of major precipitation events in the GIS used as input to hydrologic models. The issues of atmospheric precipitatio and meteorological radars are discussed in the literature review, which explains selected basic concepts and principles of these topics.

The paper details the usage of mmWave radars to track people and monitor their movement through predefined zones of interest. The theoretical part describes the physical nature of the technology and then describes algorithms which can be used to monitor using it to monitor the movement of people. In the practical part, I have developed a concrete algorithm which can be used to monitor customer queues and cash registers in shops and inform the cashiers when their presence is needed, as well as gather impersonal GDPR-compliant data about the customer's habits. Afterwards, I have developed a visualization for the Windows platform, which can be used to communicate with the radar, manage its configuration, visualize the events in real time and perform further analysis of the measured data.

Yes / The paper presents a technique to enhance the isolation between adjacent radiating elements which is common in densely packed antenna arrays. Such antennas provide frequency beam-scanning capability needed in Multiple-Input Multiple-Output (MIMO) systems and Synthetic Aperture Radars (SARs). The method proposed here uses a metamaterial decoupling slab (MTMDS), which is located between radiating elements, to suppress mutual-coupling between the elements that would otherwise degrade the antenna efficiency and performance in both the transmit and receive mode. The proposed MTM-DS consists of mirror imaged Eshaped slits engraved on a microstrip patch with inductive stub. Measured results confirm over 9–11 GHz with no MTM-DS the average isolation (S12) is -27 dB; however, with MTM-DS the average isolation improves to -38 dB. With this technique the separation between the radiating element can be reduced to 0.66λo, where λ0 is free space wavelength at 10 GHz. In addition, with this technique there is 15% improvement in operating bandwidth. At frequencies of high impedance match of 9.95 GHz and 10.63 GHz the gain is 4.52 dBi and 5.40 dBi, respectively. Furthermore, the technique eliminates poor front-to-back ratio encountered in other decoupling methods. MTM-DS is also relatively simple to implement. Assuming adequate space is available between adjacent radiators the MTM-DS can be fixed retrospectively on existing antenna arrays, which makes the proposed method versatile. / Partially supported by innovation programme under grant agreement H2020-MSCA-ITN-2016 SECRET- 722424 and the financial support from the UK Engineering and Physical Sciences Research Council (EPSRC) under grant EP/E022936/1.

Synthetic Aperture Radar (SAR) is an emerging technique in remote sensing. The technology is capable of producing high-resolution images of the earth surface in all-weather conditions. Thesis work describes the present available methods for positioning and imaging targets using M-sequence UWB (Ultra-Wideband) radar signals with moving antennas and SAR algorithm to retrieve position and image of the target. M-sequence UWB radar technology used as signal source for transmission and receiving echoes of target. Pseudo random binary sequence is used as a transmitted signal. These radars have an ability to penetrate signal through natural and unnatural objects. It offers low cost and quality security system. Among a number of techniques of image retrieval in Synthetic Aperture Radar, study of Global back projection (GBP) algorithm is presented. As a time domain algorithm, GBP possesses inherent advantages over frequency domain algorithm like ability to handle long integration angle, wider bandwidth and unlimited aperture size. GBP breaks the full synthesis aperture into numbers of sub-apertures. These sub-apertures are treated pixel by pixel. Each sub-aperture is converted to a Cartesian image grid to form an image.  During this conversion the signal is treated with linear interpolation methods in order to achieve the best quality of the images. The objective of this thesis is the imaging of target using M-sequence UWB radar and processing SAR raw data using Global back projection algorithm.

Les panaches volcaniques de téphras constituent un des aléas volcaniques majeurs. Pour prévoir leur dispersion et les zones d'impacts de leurs retombées, des modèles numériques sont utilisés en opérationnel et basés sur des paramètres éruptifs, regroupés sous la notion de terme source, caractérisant l'émission des panaches. L'ensemble du terme source est cependant difficile à mesurer en temps réel. C'est pourquoi les modèles de dispersion sont souvent basés sur des scénarios d'éruptions passées et utilisent des lois empiriques reliant la hauteur des panaches avec les flux massiques à la source. Cependant, les résultats qui découlent de ces modèles sont peu contraints, moyennés sur la durée des éruptions, et souffrent de larges incertitudes. Dans cette optique, les radars Doppler, capables de sonder l'intérieur des colonnes éruptives avec des échelles spatio-temporelles fines, peuvent fournir des contraintes cruciales sur le terme source des panaches en temps réel. Ce travail de thèse traite des applications de radars volcanologiques dédiés, potentiellement transposables aux radars météorologiques communément utilisés, afin de fournir des paramètres éruptifs à la source des panaches de téphras en surveillance opérationnelle mais également pour contraindre la dynamique des colonnes éruptives et les charges internes des panaches et de leurs retombées. Une campagne de mesures au volcan Stromboli a permis de montrer les capacités d'un couplage innovant entre un disdromètre optique (Parsivel2) avec un nouveau radar Doppler à onde millimétrique (Mini-BASTA). Grâce à l'excellente résolution spatio-temporelle de Mini-BASTA (12,5 m et 1 s), des figures intermittentes de sédimentation ont été observées dans les retombées de panaches transitoires dilués. Observées également au disdromètre mesurant la vitesse et la taille des retombées, ces figures ont été reproduites en laboratoire grâce à un modèle analogique. Un modèle conceptuel de formation de thermiques de sédimentation inversés est proposé pour expliquer ces figures et implique que les processus menant à une sédimentation irrégulière typique des panaches soutenus et concentrés peuvent s'appliquer à des panaches dilués, y compris ceux issus d'éruptions Stromboliennes normales en régime transitoire. Ensuite, une caractérisation physique d'un grand nombre de particules de cendres échantillonnées à Stromboli a permis de valider les mesures de tailles et de vitesses terminales de chutes par disdromètre sur le terrain et en laboratoire, justifiant par ailleurs son utilisation opérationnelle. A partir de ces contraintes, une loi reliant les concentrations de cendres avec les facteurs de réflectivité calculés a pu être comparée aux mesures radar in situ. Les concentrations internes modale et maximale des panaches de Stromboli sont respectivement autour de 1 × 10-5 kg m-3 et 7,45 × 10-4 kg m-3, largement supérieures au seuil fixé pour la sécurité aérienne. Les concentrations en cendres des retombées s’étalent entre 1,87 × 10-8 - 2,42 × 10-6 kg m-3 avec un mode vers 4 × 10-7 kg m-3.Finalement, ce travail de thèse montre les applications opérationnelles du radar UHF VOLDORAD 2B dans le cadre de la surveillance de l'activité de l'Etna. Une méthodologie, applicable à tout radar Doppler, a été développée pour obtenir des flux de masse de téphras en temps réel à partir d’un proxy de masse, uniquement basé sur les vitesses d'éjection et puissances mesurées, calibré avec un modèle de colonne tenant compte de l'influence du vent sur les panaches. La gamme de flux trouvée pour 47 paroxysmes entre 2011 et 2015 s’étend de 2.96 × 104 à 3.26 × 106 kg s-1. A partir d’un autre modèle de colonne éruptive, Plume-MoM, les flux radar ont permis de modéliser des hauteurs des panaches de téphras émis lors de quatre paroxysmes de l'Etna cohérentes avec les observations faites en temps réel par imagerie visible et par radar en bande-X. (...) / Volcanic tephra plumes are one of the major volcanic hazards. To forecast their dispersion and the impact zones of their fallout, the numerical models used in operational monitoring are based on eruptive parameters, called the source term, characterizing the plume emission. Source term parameters are challenging to measure in real time. This is why dispersion models are often based on past eruptive scenarios and use empirical laws that relate plume heights to source mass fluxes. However, the model outputs are not well constrained, averaged over the eruption duration, and suffer from large uncertainties. In this topic, Doppler radars are capable of probing the interior of eruptive columns and plumes at high space-time resolution and can provide crucial constraints on the source term in real time. This thesis deals with applications in operational monitoring of dedicated volcanological radars, potentially transposable to most common meteorological radars, to provide eruptive parameters at the source of tephra plumes but also to constrain the dynamics and internal mass load of eruptive columns, volcanic plumes and their fallout.A measurement campaign at Stromboli volcano has shown the capabilities of an innovative coupling between an optical disdrometer (Parsivel2) and a new 3-mm wave Doppler radar (Mini-BASTA). Owing to its high spatio-temporal resolution (12.5 m and 1 s), intermittent sedimentation patterns were observed in the fallout of dilute transient plumes typical of normal strombolian activity. These features, also recorded with the disdrometer, measuring the particle settling speeds and sizes, were reproduced in the laboratory using an analog model. A conceptual model for the formation of reversed sedimentation thermals is proposed to explain these features. It implies that processes leading to irregular sedimentation typical of sustained concentrated strong plumes can be applied to dilute weak plumes, including those formed by normal transient Strombolian activity. Then, a physical characterization of a large number of ash particles sampled at Stromboli allowed the validation of particle size and terminal velocity measurements by the disdrometer in the field and in the laboratory, arguing in favor of its operational use. Then, a physical characterization of a large number of ash particles sampled at Stromboli allowed to validate the measurements of size and terminal velocity of falls by disdrometer in the field and in laboratory, justifying also its operational use. From these constraints, a law relating ash concentrations with calculated reflectivity factors was found and compared to in situ radar measurements inside ash plumes and fallout. The modal and maximum internal concentrations of Strombolian plumes are at about 1 × 10-5 kg m-3 and 7.5 × 10-4 kg m-3 respectively, well above the threshold for aviation safety. Ash concentrations in the fallout range from 1.9× 10-8 to 2.4 × 10-6 kg m-3 with a mode at about 4 × 10-7 kg m-3.Finally, this thesis work shows operational applications of the UHF VOLDORAD 2B radar for the monitoring of explosive activity at Etna. A methodology, applicable to any Doppler radar, has been developed to obtain tephra mass eruption rates in real time from a mass proxy, based only on measured ejection velocities and power, and calibrated with an eruptive column model taking crosswinds into account. Tephra mass fluxes found for 47 paroxysms between 2011 and 2015 range from 3 × 104 to over 3 × 106 kg s-1. Then, tephra plumes heights of four Etna paroxysms were simulated using the eruptive column model Plume-MoM from the radar-derived mass eruption rates and were found consistent with real-time observations made by visible imagery and by X-band radar. This last part demonstrates the capabilities of VOLDORAD 2B to provide quantitative input parameters for dispersion models in the case of future Etna paroxysms. (...)

This thesis describes the construction of a mobile Insect Monitoring Radars (IMR) and investigations of: the reliability of IMRs for observing insect migration in inland Australia; possible biases in IMR migration estimates; the relation between an insect???s size and its radar properties; radar discrimination between insect species; the effect of weather on the migrations of Australian plague locusts and of moths; the scale of these migrations; and here IMRs are best located. The principles of entomological radar design, and the main features of insect migration in inland Australia, are reviewed. The main procedures used in the study are: calculation of radar performance and of insect radar cross sections (RCSs); reanalysis of a laboratory RCS dataset; statistical analysis of a fouryear dataset of IMR and weather observations; and a field campaign using both two existing fixed IMRs and the new mobile unit. Statistical techniques used include correlation, multiple regression, discriminant analysis, and principal components analysis. The original results of this work include design details of the mobile IMR, extension of radar performance calculations to IMRs and evaluation of flight speed biases, a holistic approach to IMR design, the relation of insect RCS magnitudes and polarization patterns to morphological variables, an estimate of the accuracy of the retrieved parameters, evaluations of three approaches (oneparameter, theory-based, and a novel two-stage method) to target identification, and verification of inferred target identities using results from nearby light traps. Possible sites for future IMRs are identified. The major conclusions are that: a mobile IMR can be built with a performance equal to that of a fixed IMR but at half the cost; significant biases in the signal processing results arise from insect speed; locusts and moths can be distinguished if all RCS parameters are used; IMRs can be designed to match particular requirements; weather has a significant effect on insect migration, the best single predictor of insect numbers being temperature; moonlight has no effect; the spatial correlation of migration properties falls to 50% at a separation of 300 km; and migrating insects can be carried by the wind for 500 km in a single night