Thesis (Ph.D.) - University of Queensland, 2007. / Includes bibliography.

Dissertation (Ph.D.) -- Worcester Polytechnic Institute. Abstract: National security needs dictate the development of new radar systems capable of identifying and tracking exoatmospheric threats to aid our defense. These new radar systems feature reduced noise floors, electronic beam steering, and ultra-wide bandwidths, all of which facilitate threat discrimination. However, in order to identify missile attributes such as RF reflectivity, distance, and velocity, many existing processing algorithms rely upon narrow bandwidth assumptions that break down with increased signal bandwidth. We present a fresh investigation into these algorithms for removing bandwidth limitations and propose novel state-space and direct-data factoring formulations such as: the multidimensional extension to the Eigensystem Realization Algorithm; employing state-space models in place of interpolation to obtain a form which admits a separation and isolation of solution components; and side-stepping the joint diagonalization of state transition matrices, which commonly plagues methods like multidimensional ESPRIT. We then benchmark our approaches and relate the outcomes to the Cramer-Rao bound for the case of one and two adjacent reflectors to validate their conceptual design and identify those techniques that compare favorably to or improve upon existing practices. / Keywords: State-space; Super resolution; Doppler; Direction of arrival; DoA; Singular value; SVDl; DSS. . Includes bibliographical references (leaves 86-91).

L'étude de la neige est un domaine important de la recherche en hydrologie et en météorologie. Il a été démontré que les propriétés physiques de la neige peuvent être récupérées en utilisant des capteurs à micro-ondes actifs. Cela nécessite une compréhension de l'interaction entre les ondes électromagnétiques (EM) et les milieux naturels. Dans ce but, le travail est divisé en deux étapes: étudier numériquement tous les modèles physiques de l'interaction onde-neige et développer un algorithme de diffusion inverse afin d’estimer la profondeur de la neige à partir de mesures de rétrodiffusion par un radar à des fréquences et angles d'incidence différents. L’objectif de la première partie consiste à effectuer les calculs de diffusion à l’aide d’un simulateur électromagnétique bien connu Ansoft High Frequency Structure Simulator (HFSS). Les simulations numériques prennent en considération: la permittivité effective de la neige, les phénomènes de diffusion surfacique dans des structures en couche des milieux homogènes (air-neige-sol) avec interfaces rugueuses ainsi que les phénomènes de diffusion volumique en traitant de la neige comme milieu dense. Par suite, le problème critique dans cette partie est de tester la validité des modèles théoriques à travers une configuration numérique adéquate.Dans la deuxième partie de ce travail, l'étude est étendue pour développer une méthode de récupération pour estimer l'épaisseur de la neige au-dessus du sol en utilisant la technique de mesures en rétrodiffusion en bande L et X (1,5 et 10 GHz) à des angles d'incidence différents. Le signal rétrodiffusé par la neige est influencé par: la diffusion surfacique, la diffusion volumique et les effets du bruit du système radar. Pour cela, le coefficient de rétrodiffusion du milieu est modélisé statistiquement en ajoutant un blanc bruit de fond gaussien (WGN) dans la simulation. Cet algorithme de diffusion inverse nécessite deux étapes de calcul. La première étape consiste à estimer la densité de la neige en utilisant le coefficient de rétrodiffusion co-polarisé en bande L à incidence normale. La deuxième étape consiste à estimer l'épaisseur de la neige à partir de coefficients de rétrodiffusion co-polarisés dans la bande X en utilisant deux différents angles d'incidence. Pour une variance de bruit de fond de 0,02, toutes les valeurs récupérées ont une erreur inférieure à 2% pour une gamme de profondeur de la neige de [50-300] cm. Cet algorithme a été vérifié par simulation à l'aide d’un logiciel de conception au niveau système, SystemVue. / Study of snow is an important domain of research in hydrology and meteorology. It has been demonstrated that snow physical properties can be retrieved using active microwave sensors. This requires an understanding of the interaction between electromagnetic (EM) waves with natural media. The objective of this work is two-fold: to study numerically all physical forward models concerning the EM wave interaction with snow and to develop an inverse scattering algorithm to estimate snow depth based on radar backscattering measurements at different frequencies and incidence angles. For the first part, the goal is to solve the scattering calculations by means of the well-known electromagnetic simulator Ansoft High Frequency Structure Simulator (HFSS). The numerical simulations include: the effective permittivity of snow, surface scattering phenomena in layered homogeneous media (air-snow-ground) with rough interfaces, and volume scattering phenomena when treating snow as a dense random media. So, the critical issue for the first part of this thesis is testing the validity of theoretical models through a careful numerical setup.For the second part, the study is extended to develop a retrieval method to estimate snow thickness over ground from backscattering observations at L- and X-band (1.5 and 10 GHz) using multiple incidence angles. The return signal from snow over ground is influenced by: surface scattering, volume scattering, and the noise effects of the radar system. So, the backscattering coefficient from the medium is modelled statistically by including a white Gaussian noise (WGN) into the simulation. This inversion algorithm involves two steps. The first is to estimate snow density using L-band co-polarized backscattering coefficient at normal incidence. The second is to estimate snow depth from X-band co-polarized backscattering coefficients using two different incidence angles. For a 0.02 noise variance, all retrieved values have an error less than 2% for a snow depth range of [50-300] cm. This algorithm was verified by simulating using Agilent’s SystemVue electronic system level design software.

Made available in DSpace on 2014-12-02T11:16:47Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-06-11Bitstream added on 2014-12-02T11:21:35Z : No. of bitstreams: 1 000800048.pdf: 3915803 bytes, checksum: caa7df2bd754d00c76832ff751fc7611 (MD5) / Este trabalho tem por objetivo examinar o uso das previsões de precipitação fornecidas pelo modelo n umérico de previsão do tempo ETA , para a agricultura , especialmente no que se refere à irrigação . O modelo ETA utilizado neste trabalho foi configurado c om a parametrização d a convecção de Kain - Fritsch, resolução horizontal de 10km x 10 k m, e 38 níveis na vertical. As previsões de precipitação acumulada em 24h do modelo ETA foram confrontadas com os dados de precipitação do radar meteorológico do Instituto de Pesquisas Meteoro lógicas da Unesp/Bauru (IPMet) , os quais foram obtidos usando a relação Z - R Rosenfeld , que pareceu a mais apropriada para a região estudada , dentre as demais relações Z - R testadas, como a Z - R Marshall - Palmer. Além de escolher a Z - R Rosenfeld , a s estimativas da precipitação pelo radar usando a relação Z - R foram corrigidas usando uma equação de regressão linear , desenvolvida com os dados de precipitação medida em três estações meteo rológicas disponíveis . O uso dessa equação é sugerido na solução de problemas práticos , tais como o cálculo de precipitação mensal no monitoramento climático. Esse procedimento permitiu reduzir significativamente a tendência que a relação Z - R escolhida ten de a subestimar a precipitação. O resultado da verificação do ETA mostra que q uando se considera somente a ocorrência do fenômeno chuva, independente da sua quantidade, o índice de acerto do modelo é em torno de 60 % para os dois primeiros dias de previsão e ligeiramente menor para o terceiro dia. Entretanto, quando a previsão da quantidade de precipitação é confrontada com a do radar, a percentagem de acerto na maior parte da área verificada não alcança mais que 50% . Além da verificação do modelo ETA propriamente dito, o trabalho a presenta uma metodologia de pesquisa que poderá futuramente ser ... / This work aims to determine the potential use of rainfall forecasts provided by the numerical model of weather prediction ETA, especially regarding irrigation in agriculture. The ETA model was configured with Kain - Fritsch convection parameterization and run with 10km x 10km horizontal resolution, and 38 vertical levels. The ETA 24h accumulated rainfall was compared to radar data precipitation from the Institute of Meteorological Research of the São Paulo State University (IPMet/UNESP), which were obtained using the Z - R Rosenfeld relationship that proved to be more appropriate than others, such as Marshal - Palmer. The systematic error of the radar precipitation data was corrected by using a linea r regression approximation, which statistically adjust these data to gauge rainfall data from three weather stations available. Some applications of this equation to practical problems solution are suggested, such as the calculation of monthly precipitatio n for climate monitoring in the radar resolution. This procedure allowed reducing the chosen ZR tend to underestimate precipitation. The verification result shows that when one considers only the occurrence of the rain phenomenon, regardless its amount, t he percentage of the success of ETA is around 60% for the first two days of the forecast and slightly lower for the third day. However, when the rainfall amount of the model is confronted with the radar precipitation, the percentage of the success most of time does not reach 50%, suggesting the need for substantial model improvement before being considered a useful source for issues related to irrigation. Besides the verification of the ETA model, the work presents a methodology that could be used in the e valuation of other models, in order to verify their potential in agriculture ...

Orientador: João Eduardo Machado Perea Martins / Banca: Reinaldo Bomfim da Silveira / Banca: Shigetoshi Sugahara / Banca: João Carlos Cury Saad / Banca: Dinival Martins / Resumo: Este trabalho tem por objetivo examinar o uso das previsões de precipitação fornecidas pelo modelo n umérico de previsão do tempo ETA , para a agricultura , especialmente no que se refere à irrigação . O modelo ETA utilizado neste trabalho foi configurado c om a parametrização d a convecção de Kain - Fritsch, resolução horizontal de 10km x 10 k m, e 38 níveis na vertical. As previsões de precipitação acumulada em 24h do modelo ETA foram confrontadas com os dados de precipitação do radar meteorológico do Instituto de Pesquisas Meteoro lógicas da Unesp/Bauru (IPMet) , os quais foram obtidos usando a relação Z - R Rosenfeld , que pareceu a mais apropriada para a região estudada , dentre as demais relações Z - R testadas, como a Z - R Marshall - Palmer. Além de escolher a Z - R Rosenfeld , a s estimativas da precipitação pelo radar usando a relação Z - R foram corrigidas usando uma equação de regressão linear , desenvolvida com os dados de precipitação medida em três estações meteo rológicas disponíveis . O uso dessa equação é sugerido na solução de problemas práticos , tais como o cálculo de precipitação mensal no monitoramento climático. Esse procedimento permitiu reduzir significativamente a tendência que a relação Z - R escolhida ten de a subestimar a precipitação. O resultado da verificação do ETA mostra que q uando se considera somente a ocorrência do fenômeno chuva, independente da sua quantidade, o índice de acerto do modelo é em torno de 60 % para os dois primeiros dias de previsão e ligeiramente menor para o terceiro dia. Entretanto, quando a previsão da quantidade de precipitação é confrontada com a do radar, a percentagem de acerto na maior parte da área verificada não alcança mais que 50% . Além da verificação do modelo ETA propriamente dito, o trabalho a presenta uma metodologia de pesquisa que poderá futuramente ser ... / Abstract: This work aims to determine the potential use of rainfall forecasts provided by the numerical model of weather prediction ETA, especially regarding irrigation in agriculture. The ETA model was configured with Kain - Fritsch convection parameterization and run with 10km x 10km horizontal resolution, and 38 vertical levels. The ETA 24h accumulated rainfall was compared to radar data precipitation from the Institute of Meteorological Research of the São Paulo State University (IPMet/UNESP), which were obtained using the Z - R Rosenfeld relationship that proved to be more appropriate than others, such as Marshal - Palmer. The systematic error of the radar precipitation data was corrected by using a linea r regression approximation, which statistically adjust these data to gauge rainfall data from three weather stations available. Some applications of this equation to practical problems solution are suggested, such as the calculation of monthly precipitatio n for climate monitoring in the radar resolution. This procedure allowed reducing the chosen ZR tend to underestimate precipitation. The verification result shows that when one considers only the occurrence of the rain phenomenon, regardless its amount, t he percentage of the success of ETA is around 60% for the first two days of the forecast and slightly lower for the third day. However, when the rainfall amount of the model is confronted with the radar precipitation, the percentage of the success most of time does not reach 50%, suggesting the need for substantial model improvement before being considered a useful source for issues related to irrigation. Besides the verification of the ETA model, the work presents a methodology that could be used in the e valuation of other models, in order to verify their potential in agriculture ... / Doutor

Orientadores: Rafael Santos Mendes, João Bosco Ribeiro do Val / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-22T19:45:23Z (GMT). No. of bitstreams: 1 Pompeo_BrunoSuarez_M.pdf: 6905835 bytes, checksum: 5e239e161c70da4b62932eb7a24b0130 (MD5) Previous issue date: 2013 / Resumo: Radares cognitivos multifuncionais são considerados a próxima geração de sistemas de radar. Atualmente, ao redor do mundo, muitas pesquisas estão voltadas para esses tipos de sistemas. Sendo assim, _e de suma importância que o Brasil também comece a pesquisar sistemas dessa natureza. O presente trabalho insere-se nesse contexto, propondo duas principais contribuições: O agendamento das tarefas de busca e rastreio de vetores aéreos levando em consideração parâmetros operacionais e critérios de priorização e a otimização na criação do diagrama de antena gerado por um arranjo de antenas. O primeiro consiste na criação de uma função objetivo que gera a ordem de atividades a serem efetuadas pelo sistema de radar. Dessa forma, essa decisão é feita automaticamente pelo sistema, podendo o operador interferir ou não. Após decidida a ordem das tarefas a serem realizadas, o diagrama de antena é modificado, respeitando certos requisitos impostos pelo operador ou pelo cenário, alterando as alimentações dos elementos ativos do arranjo de antena, no intuito de realizar a atividade de forma otimizada. Para demonstrar a integração dos dois procedimentos citados, um simulador foi desenvolvido para servir como um modelo simples e operacional de um radar cognitivo. Analisam-se os resultados obtidos em alguns cenários propostos no trabalho / Abstract: Multifunction Cognitive Radar refers to the next generation of radar systems. Many current researches are focused on these types of systems around the world. Therefore, it is extremely important that Brazil begins studying such systems. Within this context, the present work proposes two main contributions: Scheduling tasks of searching and tracking of targets based on operational parameters and prioritization criteria and Pattern optimization in phased array antennas. The former consists in creating an objective function that generates the scheduling tasks to be performed by the radar system. Thus, this decision is automatically made and the operator could or could not interfere. The latter consists in changing the antenna pattern, complying with requirements imposed by operator or environment, feeding the actives elements with phase and amplitude calculated to optimize it, after the tasks were chosen. In order to demonstrate the above procedures integration, a simulator was developed and will be used as a simple cognitive radar operational model. It were analyzed the results obtained in some scenarios proposed in the present work / Mestrado / Automação / Mestre em Engenharia Elétrica

[pt] O rastreio automático de alvos com radares de vigilância implica basicamente em quatro fases distintas: a extração de sinais (ecos) radar em áreas delimitadas previamente estabelecidas no campo de vídeo radar; a detecção por limiar e por integração binária de alvos num meio ruidoso de modo a satisfazer uma determinada probabilidade de falsos alarmes; a determinação das coordenadas geográficas dos alvos detectados; e a predição de novas áreas onde, provavelmente, estarão os alvos durante a próxima rotação da antena do radar. O presente trabalho consiste no desenvolvimento de um sistema de rastreio automático, controlado por um microcomputador, capaz de executar as quatro fases descritas. / [en] The automatic tracking of targets using surveillance radars leads basically to four distinct phases: the extraction of radar signals (echoes) within areas previoisly established in the radar display; the detection of targets in a noisy medium by threshold and improved by binary integration in order to satisfy a fixed probability of false alarms; the comutation of geographic coordinates of detected targets; and the prediction of other areas where, probably, will be the targets during the following scanning of the radar antenna. This work consists in the development of an automatic tracking system, controlled by a microcomputer, capable of doing the four phases described above.

This thesis describes the interfacing of an IBM compatible microcomputer to a BR Communications chirp sounder. The need for this is twofold: Firstly for control of the sounder including automatic scheduling of operations, and secondly for data capture. A signal processing card inside the computer performs a Fast Fourier Transform on the sampled data from two phase matched receivers. The transformed data is then transferred to the host computer for further processing, display and storage on hard disk or magnetic tape, all in real time. Critical timing functions are provided by another card in the microcomputer, the timing controller. Built by the author, the design and operation of this sub-system is discussed in detail. Additional circuitry is required to perform antenna and filter switching, and a possible design thereof is also presented by the author. The completed system, comprising the chirp sounder, the PC environment, and the signal switching circuitry, has a dual purpose. It can operate as either a meteor radar, using a fixed frequency (currently 27,99 MHz), or as an advanced chirp ionosonde allowing frequency sweeps from 1,6 to 30 MHz. In the latter case fixed frequency doppler soundings are also possible. Examples of data recorded in the various modes are given.

No description available.

No description available.