Orientadores: Hugo Enrique Hernandez Figueroa, Arismar Cerqueira Sodre Junior / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e Computação / Made available in DSpace on 2018-08-13T10:26:45Z (GMT). No. of bitstreams: 1 Brianeze_JulianoRodrigues_M.pdf: 7661922 bytes, checksum: 0d973e2e61c313de34e1ff70e57df18f (MD5) Previous issue date: 2008 / Resumo: Sistemas embarcados usando Radar de Abertura Sintética (Synthetic Aperture Radar - SAR), em plataformas aerotransportadas ou orbitais, têm sido cada vez mais usados para sensoriamento remoto. Quando estes sistemas são aplicados para estudos de cobertura vegetal e biomassa, sinais com freqüências acima de 1 GHz penetram pouco na vegetação. Já o uso de freqüências na banda P (400 MHz) permite uma maior penetração, possibilitando a detecção da superfície do terreno subjacente. A escolha da antena para esses sistemas é um ponto muito importante, já que vários de seus parâmetros estão diretamente ligados ao desempenho do sistema. O objetivo deste trabalho é propor um novo tipo de antena Yagi que seja eficiente para sistemas SAR aerotransportados: uma combinação das antenas Quasi-Yagi e Yagi-Uda. Da primeira é mantido o balun de microfita, que garante uma grande largura de banda. Já os elementos radiantes (driver e diretores), permanecem semelhantes aos de uma antena Yagi-Uda, ou seja, dipolos cilíndricos de metal. A antena foi projetada para ser fixada ao corpo de uma aeronave, usando a fuselagem para moldar seu padrão de radiação. Após a proposta de um modelo final para a nova antena Yagi, chamado Yagi Tridimensional, suas principais características foral analisadas através de simulações numéricas e experimentos. A antena proposta possui características inovadoras que permitem uma menor radiação para baixo da plataforma, possibilitando o uso simultâneo de duas antenas, uma de cada lado da aeronave, o que diminui consideravelmente os custos operacionais. Finalmente, um protótipo foi projetado e construído para atender os requisitos de um sistema SAR especificado. Além disso, medidas de perda de retorno e padrão de radiação foram realizadas e comparadas com os resultados de simulação. / Abstract: Embedded systems using Synthetic Aperture Radar (SAR), in orbital or airborne platforms, have often been used for remote sensing. When these systems are applied to vegetal cover and biomass studies, signals with frequency above 1 GHz do not properly penetrate in the vegetation. On the other hand, the use of signals with frequencies in P band (400 MHz) allows a deeper penetration, making possible the detection of the underlying terrain surface. The antenna choice for these systems is a very important point, because several of its parameters are directly linked to the system performance. The aim of this work is to develop a new kind of Yagi antenna efficient for airborne SAR systems: a combination of Quasi-Yagi and Yagi-Uda antennas. From the first, the microstrip balun is kept, in order to ensure a large bandwidth. The radiant elements (driver and directors), remain similar to those of Yagi-Uda antenna, in other words, cylindrical metal dipoles. The antenna was designed to be fixed to an aircraft body, using the fuselage to shape its radiation pattern. A novel Yagi antenna was proposed, called Tridimensional Yagi, and its main properties were analyzed by means of numerical simulations and experiments. The proposed antenna provides a lower radiation under the platform, enabling the use of two antennas simultaneously, one at each side of the aircraft. This new feature can considerably decrease the operational costs. Finally, a prototype was designed, and built to meet the requirements of a specified SAR system. Furthermore, experiments on return loss and radiation pattern have been carried out and compared to numerical simulations. / Mestrado / Telecomunicações e Telemática / Mestre em Engenharia Elétrica

The research presented in this dissertation is on the development of advanced reduced rank adaptive signal processing for airborne radar space-time adaptive processing (STAP) and steering vector mismatch robustness. This is an important area of research in the field of airborne radar signal processing since practical STAP algorithms should be robust against various kinds of mismatch errors. The clutter return in an airborne radar has widely spread Doppler frequencies; therefore STAP, a two-dimensional adaptive filtering algorithm is required for effective clutter and jamming cancellation. Real-world effects in nonhomogeneous environments increase the number of adaptive degrees of freedom required to adequately suppress interference. The increasing computational complexity and the need to estimate the interference from a limited sample support make full rank STAP impractical. The research presented here shows that the reduced rank multistage Wiener filter (MWF) provides significant subspace compression better than any previous techniques in a nonhomogeneous environment. In addition, the impact of steering vector mismatch will also be examined on the MWF. In an airborne radar environment, it is well known that calibration errors and steering vector mismatch can seriously degrade adaptive array performance and result in signal cancellation. These errors can be caused by many non-ideal factors such as beam steering angle errors, multipath propagation, and phase errors due to array imperfections. Since the MWF centrally features the steering vector on its formulation, it is important to assess the impact of steering vector mismatch. In this dissertation, several novel techniques for increasing robustness are examined and applied to the MWF. These include derivative constraints, quiescent pattern control (QPC) techniques, and covariance matrix tapers (CMT). This research illustrates that a combination of CMT and QPC, denoted CMTQ, is very effective at mitigating the impact of steering vector mismatch. Use of CMTQ augmentation provides the steering vector mismatch robustness that we desire while improving the reduced-rank and reduced sample characteristics of the MWF. Results using Monte Carlo simulations and experimental Multichannel Airborne Radar Measurements (MCARM) data confirm that the use of CMTQ gives superior performance to steering vector errors at a much reduced rank and sample support as compared to conventional techniques. / Ph. D.

During processing of data received by an airborne radar one of the issues is that the typical signal echo from the ground produces a large perturbation. Due to this perturbation it can be difficult to detect targets with low velocity or a low signal-to-noise ratio. Therefore, a filtering process is needed to separate the large perturbation from the target signal. The traditional method include a tapered Fourier transform that operates in parallel with a MTI filter to suppress the main spectral peak in order to produce a smoother spectral output. The difference between a typical signal echo produced from an object in the environment and the signal echo from the ground can be of a magnitude corresponding to more than a 60 dB difference. This thesis presents research of how the multitaper approach can be utilized in concurrence with the minimum variance estimation technique, to produce a spectral estimation that strives for a more effective clutter suppression. A simulation model of the ground clutter was constructed and also a number of simulations for the multitaper, minimum variance estimation technique was made. Compared to the traditional method defined in this thesis, there was a slight improvement of the improvement factor when using the multitaper approach. An analysis of how variations of the multitaper parameters influence the results with respect to minimum detectable velocity and improvement factor have been carried out. The analysis showed that a large number of time samples, a large number of tapers and a narrow bandwidth provided the best result. The analysis is based on a full factorial simulation that provides insight of how to choose the DPSS parameters if the method is to be implemented in a real radar system.

Les changements dans le contexte du traitement radar aéroporté impliquent de plus en plus d'améliorations qui justifient la recherche d'une alternative au filtrage adapté, qui est le processus utilisé classiquement pour estimer les paramètres des cibles détectées. Le Compressed Sensing ouvre la perspective d'un nouveau traitement, également efficace dans les configurations de cibles multiples, avec de meilleures performances de suivi et de reconnaissance que l'approche classique. Nous cherchons à appliquer ce traitement aux formes d'onde dites à évasion de fréquence. Le choix intégral des paramètres de définition du signal transmis déterminee entièrement la matrice de mesure de la procédure du Compressed Sensing, laquelle solution fournit toutes les informations recherchées sur la scène observée. Pour chaque signal à évasion de fréquence, et d'amplitude constante, la matrice de mesure correspondante est obtenue en extrayant certaines lignes d'une matrice de Fourier étendue particulière, la matrice de Fourier 2D. La construction de la génération de la matrice de mesure est importante car le succès de la reconstruction dépend des propriétés algébriques de cette matrice. / Changes in the context of airborne radar processing implie more and more improvements that justify to look for an alternative to Matched Filtering, the process conventionally used to estimate the parameters of detected targets. Compressed Sensing suggests a new treatment, also performing in multi-target cases, with better tracking and recognition performances than classical approach. We seek to apply this treatment to step frequency waveforms. The whole choice of definition parameters for the transmitted signal entirely builds the measurement matrix of the Compressed Sensing procedure which solution gives all the sought information of the observed scene. For each step frequency signal with constant amplitude, the resulting measurement matrix is obtained by extracting some lines from a particular extended Fourier matrix, the 2D Fourier matrix. The construction of the measurement matrix generation is important since the success of the reconstruction depends on the algebraic properties of this matrix.

The Imaging Wind and RAin Profiler (IWRAP) is an airborne scatterometer system built and operated by University of Massachusetts Amherst's Microwave Remote Sensing Laboratory (MIRSL). The radar is seasonally deployed aboard one of the two National Oceanic and Atmospheric Administration (NOAA) WP-3D Orion ``Hurricane Hunter'' aircraft based out of MacDill AFB in Tampa, Florida. IWRAP is a dual-frequency, Ku- and C-band, scatterometer that uses two conically scanning antennas to estimate the ocean surface wind vectors as well as intervening rain profiles. Data that is gathered with IWRAP is used to improve current Geophysical Model Functions (GMF) or to help derive new GMFs for other undocumented incidence angles. This thesis outlines the improvements and changes made to the IWRAP system from 2009-2011. Chapter Two describes the IWRAP instrument including a description of the instrument status as of Fall 2009, and a summary of instrument operations in 2010 and 2011. Chapter Three describes hardware and software modifications to support dual-polarization. It also describes hardware-based and flight-based attempts to observe at large incidence angles. Chapter Four is an analysis of the stability of the internal calibration both during flights and over a season. System documentation is consolidated into a single technical manual in Appendix A.

No description available.

Le concept de radar passif aéroporté repose sur l’utilisation de plusieurs antennes réseau, disposées sur une plateforme en vue de couvrir un angle solide large de détection, en s’appuyant sur l’utilisation de signaux d’opportunité provenant d’émetteurs au sol. La détection aéroportée à partir de signaux d’opportunité est intéressante, notamment pour assurer l’autoprotection d’un avion ou d’un hélicoptère ; en revanche elle constitue un défi technique notamment en raison du niveau des signaux interférents, en provenance de l’émetteur et des trajets multiples indirects (le fouillis), bien supérieur au niveau de signal utile diffusé par la cible à détecter. D’autres effets, tels que la structure arbitraire des signaux (forme d’onde non-radar) et sa conséquence sur les lobes secondaires en distance, contribuent à la complexité du traitement à mettre en œuvre.Le point de départ des recherches se situe à l’intersection des techniques de radar passif (utilisant la corrélation entre un signal de référence non connu a priori et les signaux diffus renvoyés par l’environnement) et les techniques de type STAP (Space Time Adaptive Processing) utilisées pour la détection des cibles mobiles par les radars aéroportés conventionnels. Dans ce contexte, les travaux de thèse permettent d’étendre d’une part la caractérisation et la qualification des signaux « radar passif » à une configuration aéroportée, d’autre part les techniques STAP à une configuration bistatique et à des signaux de forme arbitraire et non structurés comme des signaux radar. Les recherches mettent en évidence l’importance primordiale du trajet direct et des premiers échos de fouillis qui parasitent la caractérisation spatio-temporelle des échos reçus dans la case distance de la cible sous test. La caractéristique du fouillis, habituellement tracée dans le plan Doppler-angle, se trouve affectée par ces interférences qu’il faut éliminer au préalable. Pour cela, un premier filtre à réponse finie est mis en œuvre sur chaque capteur, puis le traitement STAP est appliqué à l’ensemble du réseau d’antennes.Les traitements proposés sont simulés et les performances en détection sont analysées. Une expérimentation est conduite, à l’aide d’un réseau de 4 antennes mobiles au sol. Les conditions sont réunies pour collecter des signaux de fouillis étalés en Doppler et analyser l’effet d’une forme d’onde non-radar. Les traitements d’élimination des interférences sont mis en œuvre et ainsi qualifiés expérimentalement. / The novel concept for the airborne passive radar is to have multiple passive receiving arrays covering a 4 steradian angle around the platform which makes use of the ground-based stationary transmitter as the illuminator of opportunity. This challenging passive radar configuration would well find application for localized covert surveillance on an airborne platform such as an unmanned aerial vehicle, helicopter, etc. For the airborne passive radar, during moving target detections, it encounters the effects of strong interfering signal returns against the weak target returns where this severe interfering environment is usually characterized by the high levels of direct path and clutter against the thermal noise background. Due to the continuous wave, random and aperiodic nature of the passive signal and given the strong direct path and clutter signals, their random range sidelobes couplings into further range cells will seriously exacerbate the background interference, making target detections a big challenge. Moreover, owing to the platform motion, the clutter received by the airborne passive radar is not only extended in both range and angle, it is also spread over a region in Doppler frequency which further complicates the problem.This research work is focused on identifying and analyzing the critical issues faced by the airborne passive radar on moving target detections and to develop effective signal processing schemes for improved performance. As a first step, it is important to accurately derive the model for the received passive signals and consequently, efficient signal processing schemes can be studied to mitigate and to improve detections performance. The signal processing schemes for the airborne passive radar can be segregated into a two-step interference cancellation process where the direct path and strong clutter coupling components (and their corresponding random range sidelobes) present in the received signal at each antenna element can first be effectively suppressed by the adaptive interference cancellation algorithm prior to matched filter processing. Further cancellation on the residual random range sidelobes couplings and on the spatial-Doppler dependent clutter can be achieved using reduced-dimension STAP. Trials based on the ground-based moving passive radar experiments are conducted as the final part of this research work to validate and evaluate the signal processing schemes which is a major progress towards implementing an operational airborne passive radar.

Maritime target tracking from an airborne radar faces many issues due to the features of theenvironment, the targets to be tracked and the movement of the radar platform. Therefore, aunique tracking algorithm is not always able to reach the best possible performance for everyencountered situation. It needs to self-adapt to the environment and to the targets which areobserved in order to always be as ecient as possible. Adaptability is thus a key issue of radartracking.Several implementations of the mathematical Bayesian estimation theory, commonly called lters,have been used in the literature in order to estimate as precisely as possible targets trajectory.Depending on the situations and the assumptions that are considered, some of themare expected to perform better. This thesis suggests to look deeper into the tracking techniquesthat can be found in the literature and compare them in order to dene more precisely the advantagesof each of them over the others. This should enable to wisely choose the method thatis most likely to provide the best performance for a given situation. In particular, the nonlinearconversion between the Cartesian coordinates with which the state vector is dened and thespherical coordinates used for the measurements is investigated. A measure of nonlinearity isintroduced, studied and used to compare the extended Kalman lter and the particle lter.The size of the detected maritime targets is a special feature that makes it possible to draw amaneuverability-based classication which enables to adapt the tracking technique to be used.Joint tracking and classication (JTC) has already been described in the literature with a specicmeasurement model. This thesis makes this model more realistic using a random distribution ofthe reection point on the target's shape. The tracking method is modied to take into accountthis new measurement model and some simulations are run.This modied JTC algorithm proves to be more ecient than the JTC structure presented inthe literature. Eventually, this thesis shows that nonlinearity is a paramount issue that needsto be considered to implement an ecient self-adapatable radar tracking algorithm, this beingespecially true for extended targets. / Maritim malfoljning fran en luftburen radar star infor manga problem pa grund av miljons karaktar, de mal som ska sparas och radarplattformens rorelse. Darfor kan en unik sparningsalgoritminte na basta mojliga prestanda for varje situation som uppstar. Den maste anpassa sig sjalvtill miljon och till de mal som overvakas for att bli sa eektiv som mojligt. Anpassningsformagaar alltsa en viktig fraga inom radarsparning.Flera implementeringar av den matematiska Bayesianska berakningsteorin, vanligtvis kalladelter, har anvants i litteraturen for att forutsaga malbanor sa exakt som mojligt. Beroendepa situationer och antaganden som beaktas forvantas vissa av dem bli battre. Denna avhandlingforeslar att noggrant undersoka sparningsteknikerna som kan hittas i litteraturen ochjamfora dem for att mer precist deniera fordelarna av var och en framfor de andra. Det skulleunderlatta ett klokt val av metoden som mest sannolikt ger basta prestanda for varje given situation.Sarskilt undersoks den icke-linjara omvandlingen mellan kartesiska koordinatsystemet,som denierar tillstandsvektorn, och sfariska koordinater som anvands for matningarna. Ettmatt pa icke-linjaritet presenteras, studeras och anvands for att jamfora ett utokat Kalmanltermed partikelltret.Storleken pa de detekterade maritima malen ar en speciell egenskap som gor det mojligt attgora en klassicering baserad pa manovrerbarhet som hjalper till att anpassa sparningsteknikensom ska anvandas. Simultan foljning och klassiering, "joint tracking and classication" (JTC)pa engelska, har redan beskrivits i litteraturen med en specik matmodell. Denna avhandlinggor modellen mer realistisk med hjalp av en slumpmassig fordelning av reektionspunkten pamalets form. Sparningsmetoden ar modierad for att beakta denna nya matmodell och nagrasimuleringar utfors.Denna modierade JTC-struktur visar sig mer eektiv an JTC-strukturen som presenteras ilitteraturen. Slutligen visar denna avhandling att icke-linjaritet ar en viktig fraga som mastebeaktas for att erhalla en eektiv radarsparningsalgoritm som kan anpassa sig sjalv. Dettagaller sarskilt for utstrackta mal.