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  • Geosynchronous SAR focusing with atmospheric phase screen retrieval and compensation

     Ruiz Rodon, Josep; Broquetas Ibars, Antoni; Monti Guerneri, Andrea; Rocca, Fabio
    IEEE transactions on geoscience and remote sensing
    Date of publication: 2013
    Journal article

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    In this paper, a geosynchronous synthetic aperture radar (SAR) (GEOSAR) mission for atmospheric phase screen (APS) retrieval using a long coherent integration of pulses is analyzed. The nearly fixed position of the geosynchronous platforms makes GEOSAR systems suitable for continuous monitoring applications. However, using moderate transmitted powers and antenna sizes, very long integration times up to hours are required. In GEOSAR, the two-way propagation of radar signals can decorrelate significantly due to atmospheric changes during the long data take, resulting in an APS which can cause image defocusing and artifacts. In this paper, the APS effects are analyzed, and an APS correction algorithm from short-term periodic acquisitions (subapertures) of the whole long-term GEOSAR synthetic aperture is described. The results obtained from the APS retrieval algorithm in a simulated GEOSAR acquisition affected by atmospheric decorrelation are presented. Finally, an experimental test of the APS algorithm performance with a long-integration ground-based SAR acquisition is shown.

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    ARBRES: Light-weight CW/FM SAR sensors for small UAVs  Open access

     Aguasca Sole, Alberto; Acevo Herrera, René; Broquetas Ibars, Antoni; Mallorqui Franquet, Jordi Joan; Fabregas Canovas, Francisco Javier
    Sensors
    Date of publication: 2013-03-06
    Journal article

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    This paper describes a pair of compact CW/FM airborne SAR systems for small UAV-based operation (wingspan of 3.5 m) for low-cost testing of innovative SAR concepts. Two different SAR instruments, using the C and X bands, have been developed in the context of the ARBRES project, each of them achieving a payload weight below 5 Kg and a volume of 13.5 dm3 (sensor and controller). Every system has a dual receiving channel which allows operation in interferometric or polarimetric modes. Planar printed array antennas are used in both sensors for easy system integration and better isolation between transmitter and receiver subsystems. First experimental tests on board a 3.2 m wingspan commercial radio-controlled aircraft are presented. The SAR images of a field close to an urban area have been focused using a back-projection algorithm. Using the dual channel capability, a single pass interferogram and Digital Elevation Model (DEM) has been obtained which agrees with the scene topography. A simple Motion Compensation (MoCo) module, based on the information from an Inertial+GPS unit, has been included to compensate platform motion errors with respect to the nominal straight trajectory.

  • An efficient method for the azimuth compression of geosynchronous SAR data through sub-apertures processing

     Belotti, Michele; Broquetas Ibars, Antoni; Leanza, Antonio; Monti Guarnieri, Andrea; Recchia, Andrea; Rocca, Fabio; Ruiz Rodon, Josep; Tebaldini, Stefano
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2013-07-21
    Presentation of work at congresses

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    We propose an efficient method for the azimuth compression and Atmospheric Phase Screen estimation of Geosynchronous SAR data. The method is based on the iterative processing of sub-apertures of increasing size, allowing to gradually refine the quality of the focused data and of the estimated APS. The whole processing can be easily parallelized. Results over simulated data are shown. © 2013 IEEE.

  • Radiometric and spatial resolution constraints in millimeter-mave close-range passive screener systems

     Nova Lavado, Enrique; Romeu Robert, Jordi; Torres Torres, Francisco; Pablos Hernandez, Miriam; Riera Salis, Jose Manuel; Broquetas Ibars, Antoni; Jofre Roca, Luis
    IEEE transactions on geoscience and remote sensing
    Date of publication: 2013-04
    Journal article

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    This paper presents a comparative study of the radiometric sensitivity and spatial resolution of three near-field (NF) passive screener systems: real aperture, 1-D synthetic aperture (SA), and 2-D SA radiometers are compared. The analytical expressions for the radiometric resolution, the number of required antennas, and the number of pixels in the image are derived taking into account the distortion produced by the NF geometry at nonboresight directions where the distortion is dominant. Based on the theoretical results, a performance comparison among the studied systems is carried out to show the advantages and drawbacks when using the radiometers in a close-range screening application. Moreover, the screener performance in a close-range environment is discussed from the results obtained in the aforementioned comparison.

  • Terahertz Integrated Antenna Arrays for Imaging Applications

     Alonso Del Pino, Maria
    Defense's date: 2013-10-25
    Department of Signal Theory and Communications, Universitat Politècnica de Catalunya
    Theses

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  • Analysis and design of an edge-technique-based Doppler wind lidar. Practical assessment of a laboratory prototype  Open access

     Muñoz Porcar, Constantino
    Defense's date: 2013-02-22
    Department of Signal Theory and Communications, Universitat Politècnica de Catalunya
    Theses

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    This thesis is the initial stage in the development of a range-resolving Doppler wind lidar. Atmospheric lidars emit pulsed laser radiation that after being scattered by air molecules and suspended aerosol particles is partly collected by a telescope, detected by a photoreceiver and analyzed for obtaining information about the state of the illuminated region. The speed of these elements with respect the instrument can be identified with the speed of the wind and it can be therefore measured ¿and this is the way the Doppler wind lidars do it¿¿ from the detection of the frequency shift that due to Doppler effect is undergone by the scattered signal. The selection of the technique used to measure this optical frequency shift ¿the so-called edge-technique¿¿ has been determined in this case mainly by the available laser, the location of the site where the system will be placed and by simplicity considerations. With this technique, the frequency difference between the emitted pulses and the receiver signal is obtained by measuring the change produced in the transmission of an optical filter. In the first part of this work the design of the optical filter devoted to discriminate frequencies and a complete analysis of the performance of a Doppler wind lidar based on the edge-technique operating from the signal scattered by the atmospheric aerosols is proposed. In the first place, a method that permits to calculate, using the precision of the measurements as indicator and the range of measurable velocities as constraint, the best configuration of the optical filter used in the system, in this case a Fabry-Perot interferometer, has been established. Afterwards, the precision, the time resolution, the range resolution and the accuracy of the velocity measurements are analyzed with detail in different typical measuring scenarios and are compared with the performance of other systems currently in operation. Also, the effects on the quality parameters of the velocity measurements of the interfering molecular return component that is unavoidably present in the analyzed aerosol signal is studied. The second part of the thesis is devoted to the design, implementation and assessment of a laboratory prototype based on the edge-technique. The objective of this development is to assess in convenient conditions the implementation of the selected detection technique. This preliminary assembly also permits to characterize and adjust the operation of some of the critical elements and subsystems that will be part of the Doppler wind lidar, such as the Fabry-Perot interferometer, the cavity tuning control subsystem (essential to compensate the relative frequency drifts between the laser and the filter), the elements for guiding and conditioning the light beams, the signal detection and amplification modules or the routines for calibrating and controlling the system and for processing the information. The prototype implemented to achieve these objectives is designed to measure the speed of hard targets using a laser emitting in continuous-wave regime. These operating conditions allow avoiding some difficulties related with the use of pulsed atmospheric lidar signals: in the first place, their duration is very short and their power is neither constant nor predictable; furthermore, it is not easy to obtain independent values of the speed of the wind for assessing the quality of the measurements.

  • GNSS Reflectometry for Land Remote Sensing Applications  Open access

     Egido Egido, Alejandro
    Defense's date: 2013-07-05
    Department of Signal Theory and Communications, Universitat Politècnica de Catalunya
    Theses

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    Soil moisture and vegetation biomass are two essential parameters from a scienti c and economical point of view. On one hand, they are key for the understanding of the hydrological and carbon cycle. On the other hand, soil moisture is essential for agricultural applications and water management, and vegetation biomass is crucial for regional development programs. Several remote sensing techniques have been used to measure these two parameters. However, retrieving soil moisture and vegetation biomass with the required accuracy, and the appropriate spatial and temporal resolutions still remains a major challenge. The use of Global Navigation Satellite Systems (GNSS) reflected signals as sources of opportunity for measuring soil moisture and vegetation biomass is assessed in this PhD Thesis. This technique, commonly known as GNSS-Reflectometry (GNSS-R), has gained increasing interest among the scienti c community during the last two decades due to its unique characteristics. Previous experimental works have already shown the capabilities of GNSS-R to sense small reflectivity changes on the surface. The use of the co- and cross-polarized reflected signals was also proposed to mitigate nuisance parameters, such as soil surface roughness, in the determination of soil moisture. However, experimental evidence of the suitability of that technique could not be demonstrated. This work analyses from a theoretical and an experimental point of view the capabilities of polarimetric observations of GNSS reflected signals for monitoring soil moisture and vegetation biomass. The Thesis is structured in four main parts. The fi rst part examines the fundamental aspects of the technique and provides a detailed review of the GNSS-R state of the art for soil moisture and vegetation monitoring. The second part deals with the scattering models from land surfaces. A comprehensive description of the formation of scattered signals from rough surfaces is provided. Simulations with current state of the art models for bare and vegetated soils were performed in order to analyze the scattering components of GNSS reflected signals. A simpli ed scattering model was also developed in order to relate in a straightforward way experimental measurements to soil bio-geophysical parameters. The third part reviews the experimental work performed within this research. The development of a GNSS-R instrument for land applications is described, together with the three experimental campaigns carried out in the frame of this PhD Thesis. The analysis of the GNSS-R and ground truth data is also discussed within this part. As predicted by models, it was observed that GNSS scattered signals from natural surfaces are a combination of a coherent and an incoherent scattering components. A data analysis technique was proposed to separate both scattering contributions. The use of polarimetric observations for the determination of soil moisture was demonstrated to be useful under most soil conditions. It was also observed that forests with high levels of biomass could be observed with GNSS reflected signals. The fourth and last part of the Thesis provides an analysis of the technology perspectives. A GNSS-R End-to-End simulator was used to determine the capabilities of the technique to observe di erent soil reflectivity conditions from a low Earth orbiting satellite. It was determined that high accuracy in the estimation of reflectivity could be achieved within reasonable on-ground resolution, as the coherent scattering component is expected to be the predominant one in a spaceborne scenario. The results obtained in this PhD Thesis show the promising potential of GNSS-R measurements for land remote sensing applications, which could represent an excellent complementary observation for a wide range of Earth Observation missions such as SMOS, SMAP, and the recently approved ESA Earth Explorer Mission Biomass.

    La humedad del suelo y la biomasa de la vegetaci on son dos parametros clave desde un punto de vista tanto cient co como econ omico. Por una parte son esenciales para el estudio del ciclo del agua y del carbono. Por otra parte, la humedad del suelo es esencial para la gesti on de las cosechas y los recursos h dricos, mientras que la biomasa es un par ametro fundamental para ciertos programas de desarrollo. Varias formas de teledetección se han utilizado para la observaci on remota de estos par ametros, sin embargo, su monitorizaci on con la precisi on y resoluci on necesarias es todav a un importante reto tecnol ogico. Esta Tesis evalua la capacidad de medir humedad del suelo y biomasa de la vegetaci on con señales de Sistemas Satelitales de Posicionamiento Global (GNSS, en sus siglas en ingl es) reflejadas sobre la Tierra. La t ecnica se conoce como Reflectometr í a GNSS (GNSS-R), la cual ha ganado un creciente inter es dentro de la comunidad científ ca durante las dos ultimas d ecadas. Experimentos previos a este trabajo ya demostraron la capacidad de observar cambios en la reflectividad del terreno con GNSS-R. El uso de la componente copolar y contrapolar de la señal reflejada fue propuesto para independizar la medida de humedad del suelo de otros par ametros como la rugosidad del terreno. Sin embargo, no se pudo demostrar una evidencia experimental de la viabilidad de la t ecnica. En este trabajo se analiza desde un punto de vista te orico y experimental el uso de la informaci on polarim etrica de la señales GNSS reflejadas sobre el suelo para la determinaci on de humedad y biomasa de la vegetaci on. La Tesis se estructura en cuatro partes principales. En la primera parte se eval uan los aspectos fundamentales de la t ecnica y se da una revisi on detallada del estado del arte para la observaci on de humedad y vegetaci on. En la segunda parte se discuten los modelos de dispersi on electromagn etica sobre el suelo. Simulaciones con estos modelos fueron realizadas para analizar las componentes coherente e incoherente de la dispersi on de la señal reflejada sobre distintos tipos de terreno. Durante este trabajo se desarroll o un modelo de reflexi on simpli cado para poder relacionar de forma directa las observaciones con los par ametros geof sicos del suelo. La tercera parte describe las campañas experimentales realizadas durante este trabajo y discute el an alisis y la comparaci on de los datos GNSS-R con las mediciones in-situ. Como se predice por los modelos, se comprob o experimentalmente que la señal reflejada est a formada por una componente coherente y otra incoherente. Una t ecnica de an alisis de datos se propuso para la separacióon de estas dos contribuciones. Con los datos de las campañas experimentales se demonstr o el bene cio del uso de la informaci on polarim etrica en las señales GNSS reflejadas para la medici on de humedad del suelo, para la mayor a de las condiciones de rugosidad observadas. Tambi en se demostr o la capacidad de este tipo de observaciones para medir zonas boscosas densamente pobladas. La cuarta parte de la tesis analiza la capacidad de la t ecnica para observar cambios en la reflectividad del suelo desde un sat elite en orbita baja. Los resultados obtenidos muestran que la reflectividad del terreno podr a medirse con gran precisi on ya que la componente coherente del scattering ser a la predominante en ese tipo de escenarios. En este trabajo de doctorado se muestran la potencialidades de la t ecnica GNSS-R para observar remotamente par ametros del suelo tan importantes como la humedad del suelo y la biomasa de la vegetaci on. Este tipo de medidas pueden complementar un amplio rango de misiones de observaci on de la Tierra como SMOS, SMAP, y Biomass, esta ultima recientemente aprobada para la siguiente misi on Earth Explorer de la ESA.

  • Radiometric and spatial resolution constraints in millimeter-wave close-range passive screener systems

     Nova Lavado, Enrique; Romeu Robert, Jordi; Torres Torres, Francisco; Pablos, M.; Riera, J.M.; Broquetas Ibars, Antoni; Jofre Roca, Luis
    IEEE transactions on geoscience and remote sensing
    Date of publication: 2013-04
    Journal article

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    This paper presents a comparative study of the radiometric sensitivity and spatial resolution of three near-field (NF) passive screener systems: real aperture, 1-D synthetic aperture (SA), and 2-D SA radiometers are compared. The analytical expressions for the radiometric resolution, the number of required antennas, and the number of pixels in the image are derived taking into account the distortion produced by the NF geometry at nonboresight directions where the distortion is dominant. Based on the theoretical results, a performance comparison among the studied systems is carried out to show the advantages and drawbacks when using the radiometers in a close-range screening application. Moreover, the screener performance in a close-range environment is discussed from the results obtained in the aforementioned comparison.

  • Results on spatial-temporal atmospheric phase screen retrieval from long-term GEOSAR acquisition

     Ruiz Rodon, Josep; Broquetas Ibars, Antoni; Makhoul Varona, Eduardo; Monti Guarnieri, Andrea; Rocca, Fabbio
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2012-07-25
    Presentation of work at congresses

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    In this paper, a high integration gain GEOSAR mission for Earth imaging is presented. The spatial-temporal atmospheric decorrelation issues of a long integration time GEOSAR mission must be carefully studied. The feasibility of a GEOSAR mission for Atmospheric Phase Screen retrieval purposes is studied. The raw data received from several hours of acquisition is divided into sub-acquisitions with integration time on the order of the APS decorrelation time. From each sub-matrix, a low-resolution but enough to sample the spatial variations of the atmospheric map is obtained. The simulated results of the APS retrieval from a GEOSAR acquisition are shown at the end of this paper.

  • Evaluation of state-of-the-art GMTI techniques for future spaceborne SAR systems -simulation validation-

     Makhoul Varona, Eduardo; Broquetas Ibars, Antoni; González, Oriol
    European Conference on Synthetic Aperture Radar
    Presentation's date: 2012-04-25
    Presentation of work at congresses

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    This paper presents an evaluation of the state-of-the-art Ground Moving Target Indication (GMTI) techniques in the frame of space-borne Synthetic Aperture Radar (SAR) for vessel detection by means of a flexible SAR-GMTI simulator tool. Among the different GMTI techniques, Displaced Phase Center Antenna (DPCA), Along-Track Interferometry (ATI) and Imaging Space-Time Adaptive Processing (ISTAP) have been evaluated

  • Optical cross-correlation of millimeter wave signals applied to interferometric radiometry

     Nova, Enrique; Romeu Robert, Jordi; Torres Torres, Francisco; Broquetas Ibars, Antoni; Jofre Roca, Luis
    International Conference on Infrared, Millimeter, and Terahertz Waves
    Presentation's date: 2012-07
    Presentation of work at congresses

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    This paper presents a method to perform in the opti- cal domain the correlations required when processing millimeter wave interferometric radiometer signals. The main problem when addressing the design of an interferometric radiometer working at W-band resides on the distribution and correlation of large bandwidth signals acquired by each radiometer receiver. In order to avoid the necessity of baseband processing of signals with large relative bandwidths, the signals coming from the radiometric receivers are up-converted to the optical domain using LiNbO3 optical phase modulators. The modulated signals from each receiver pairs are added and and detected by a photodiode. The correlation is obtained from the resulting photocurrent.

  • Ground moving target indication using multi-channel SAR with non-uniform displaced phase centers

     Makhoul Varona, Eduardo; Broquetas Ibars, Antoni; Ruiz Rodon, Josep
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2012-07-24
    Presentation of work at congresses

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    This paper presents an evaluation of a post-Doppler spacetime adaptive Processing (STAP) technique for non-uniformly displaced phase center receivers synthetic aperture radar (SAR). Both theoretical and simulation analysis are carried out in order to prove the ground moving target indication (GMTI) capabilities for specific non-uniformly spaced multichannel configurations on-board a single satellite platform. Simulated SAR data in the maritime scenario show improved performance, specially for small and slow targets, compared to current SAR missions, equipped with just two channels.

  • GEMINI: geosynchronous SAR for Earth monitoring by interferometry and imaging

     Monti Guarnieri, Andrea; Tebaldini, Stefano; Rocca, Fabio; Broquetas Ibars, Antoni
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2012-07-23
    Presentation of work at congresses

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    In this paper we discuss a preliminary design for a constellation of geosynchronous (GEO) Synthetic Aperture Radars (SAR). The key design concept is to employ one or more pairs of closely-spaced twin receivers flown onboard GEO minisatellites moving with a velocity of few meters per second with respect to the Earth’s surface, so as to form a synthetic aperture on the order of few tenths of kilometers twice a day. The employement of closely-spaced receivers would enable the estimation of the temporal gradient of the tropospheric delay via along track Interferometry, resulting in the possibility to coherently integrate the signal over an aperture time on the order of hours. As a result an area as wide as one thousand kilometers could be imaged while providing: i) continuous temporal coverage at coarse resolution (hundreds of meters); ii) high resolution (few meters) imaging and interferometric capabilities two or more times a day by integrating the signal over few hours, thus ensuring high SNR performance (for stable targets) with a transmitted power com- parable to currently operated spaceborne SARs.

  • Atmospheric phase screen retrieval from GEOSAR long term acquisition

     Ruiz Rodon, Josep; Broquetas Ibars, Antoni; Monti Guarnieri, Andrea; Rocca, Fabio
    European Conference on Synthetic Aperture Radar
    Presentation's date: 2012-04-25
    Presentation of work at congresses

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    In this paper, a GEOSAR mission with typical LEOSAR parameters but longer integration time to increase the received power is presented. Such systems can provide images of large areas with continuous monitoring. The revisit time is reduced to the synthetic aperture integr ation time to reach the desired resolution and SNR require- ments. However, the Atmospheric Phase Screen (APS) ar tefacts must be characterized to compensate the long term atmospheric phase decorrelation. An APS correc tion methodology from short term periodic acquisitions (sub-apertures) of the whole long term synthetic aperture is analysed. Finally, the first results obtained from Ground-Based SAR (GB-SAR) real data are presented to validate the proposed correction method.

  • Approach to velocity and acceleration measurement in the Bi-Directional SAR imaging mode

     Mittermayer, Josef; Prats, Pau; Wollstadt, Steffen; Baumgartner, Stefan; Lopez Dekker, Paco; Broquetas Ibars, Antoni; Makhoul Varona, Eduardo; Krieger, Gerhard; Moreira, Alberto
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2012-07-26
    Presentation of work at congresses

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    This paper presents an initial analysis of the possibilities for velocity and acceleration m easurement with the Bi- Directional SAR imaging mode (BiDi). It comprises single satellite single path acquisitions as well as a constellation of two satellites. The translati onal velocity components into azimuth and range directions are simulated. A BiDi ap- proach for measuring the azimuth velocity from one satellite with one receiving channel is proposed. Image examples acquired with the TerraSAR-X (TSX) and TanDEM-X (TDX) satellites show velocity and acceleration effects on ships and the proposed BiDi ve locity approach is verified. Interferometric fringes were observed on anchoring ships. A first approach into the understanding of rotational effects was achieved by simulation of rotational fringes.

  • Evaluation of the internal calibration methodologies for spaceborne synthetic aperture radars with active phased array antennas

     Makhoul Varona, Eduardo; Broquetas Ibars, Antoni; Lopez Dekker, Paco; Closa, Josep; Saameno, Paula
    IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing
    Date of publication: 2012-06
    Journal article

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  • SAR Multidimensional para la observación de la tierra: sistemas, procesado y aplicaciones

     Alonso Gonzalez, Alberto; Centolanza, Giuseppe; Monells Miralles, Daniel; López Martínez, Carlos; Mallorqui Franquet, Jordi Joan; Broquetas Ibars, Antoni; Fabregas Canovas, Francisco Javier; Makhoul Varona, Eduardo; Aguasca Sole, Alberto
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  • Track Detection in Railway Sidings Based on MEMS Gyroscope Sensors

     Broquetas Ibars, Antoni; Comeron Tejero, Adolfo; Gelonch Bosch, Antoni; Fuertes Armengol, José Mª; Castro, Jose Antonio; Felip, Damià; López, Miguel Angel; Pulido, Jose Antonio
    Sensors
    Date of publication: 2012-11-23
    Journal article

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  • A geosynchronous synthetic aperture radar mission analysis based on long integration time acquisition and atmospheric correction

     Ruiz, Josep; Broquetas Ibars, Antoni; Monti, Andrea; Rocca, Fabio
    Ka and Broadband Communications Navigation and Earth Observation Conference
    Presentation's date: 2011-10-03
    Presentation of work at congresses

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  • A Ku-band geosynchronous synthetic aperture radar mission analysis with medium transmitted power and medium-sized antenna

     Ruiz, Josep; Broquetas Ibars, Antoni; Monti Guarnieri, Andrea; Rocca, Fabio
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2011-07-24
    Presentation of work at congresses

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    In this paper, the feasibility of a geosynchronous satellite for Synthetic Aperture Radar applications is assessed. The nearly fixed position of geosynchronous satellites offers new features to SAR acquisition such as the continuous monitoring of wide areas with short revisit times. A monostatic dedicated mission, working with moderated antenna sizes and transmitted powers with long integration time (several hours), is firstly presented and the main SAR parameters (PRF selection, power budget, ambiguities) analyzed. The system Point Spread Function is obtained from simulated raw data showing the system spatial resolution in a realistic orbital configuration.

  • Micrometric deformation imaging at W-Band

     Abril, Jordi; Nova, Enrique; Broquetas Ibars, Antoni; Aguasca Sole, Alberto; Romeu Robert, Jordi; Jofre Roca, Luis
    IEEE International Microwave Workshop
    Presentation's date: 2011-08-24
    Presentation of work at congresses

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    The measurement of scattered signals at W Band can be exploited to form images of small deformations with precisions in the order of tenths of micrometers. In this paper an Interferometric Synthetic Aperture Radar setup is proposed to form high resolution reflectivity images and deformation maps of dielectric or metallic surfaces. First, the system geometry of observation based on a linear motion of the radar antennas is described. A CW frequency domain measurement provides the wide band required for high resolution imaging. The scattered field data is focused on the surface spatial domain using a combination of range compression based on Inverse Fourier Transform combined with a backprojection algorithm to form the synthetic aperture with a high cross range resolution. The focusing performance has been assessed by numerical simulations and experimental measurements of simple scattering objects like spheres and trihedrals. Interferometric images of controlled displacements have been obtained showing a good agreement between real and measured displacements. A representative surface deformation test has been also carried out using a metallic rough surface. The interferometric phase difference between acquisitions can be used to image local deformations in the order of tens of micrometers from a range of several meters. Likewise the interferogram coherence shows the degree of decorrelation of the radar reflectivity which provides valuable information for surface random change assessment.

  • W-band radiometric imager with mechanical beam-scanning

     Nova, Enrique; Abril, Jordi; Romeu Robert, Jordi; Broquetas Ibars, Antoni; Torres Torres, Francisco; Jofre Roca, Luis
    International Conference on Infrared, Millimeter, and Terahertz Waves
    Presentation's date: 2011-10-02
    Presentation of work at congresses

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    The design of a 94 GHz Total Power Radiometer system for imaging purposes is presented in this paper. A mechanical beam-scanning antenna system is used to acquire passive raster images. The main performance parameters of the imaging system are described as well as their impact on the resulting image quality. A temperature resolution below 1K and a spatial resolution around 4 cm at 1 meter standoff distance are obtained with this system. Moreover, radiometric images acquired in indoor and outdoor environments are shown and compared.

  • Characterization of a 94 GHz radiometric imager with mechanical beam-scanning

     Nova, Enrique; Abril, Jordi; Romeu Robert, Jordi; Broquetas Ibars, Antoni; Torres Torres, Francisco; Jofre Roca, Luis
    IEEE International Microwave Workshop
    Presentation's date: 2011-08-24
    Presentation of work at congresses

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    This paper presents the characterization in terms of spatial resolution and radiometric sensitivity of a W-band Total Power Radiometer (TPR). The TPR is based on a heterodyne receiver with 64 dB of gain and 6.5 dB of noise figure. An antenna system consisting on a pan-tilt scanner has been designed and built in order to aim a 100 mm offset parabolic reflector. With this system, relative temperature images of targets at a 1 m standoff range are obtained in indoor environments with an spatial resolution of 4 cm.

  • Deforming and relief interferometric SAR imaging at W-band

     Abril, Jordi; Nova, Enrique; Broquetas Ibars, Antoni; Aguasca Sole, Alberto; Romeu Robert, Jordi; Jofre Roca, Luis
    International Conference on Infrared, Millimeter, and Terahertz Waves
    Presentation's date: 2011-10-02
    Presentation of work at congresses

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    Interferometry at W Band can be exploited to form images of small deformations with precisions in the order of tenths of microns and retrieve surface relieves. An Interferometric Synthetic Aperture Radar setup is proposed in which the scattered field is focused using a combination of range compression and backpropagation algorithm. Interferometric images involving micrometric displacements have been obtained showing a good agreement between real and measured displacements. A metallic rough surface deformation test has been first performed, by imaging the phase difference between acquisitions before and after the displacement. The interferometric phase difference between acquisitions can be used to image local deformations from a range of several meters. Furthermore the interferogram coherence shows the degree of decorrelation of the radar reflectivity which provides valuable information for surface random change. Likewise the relief of the surface with an L-shape target is retrieved mapping the phase difference between the two receiving antennas, in this case an static scenario is required.

  • Internal calibration strategies for space-borne synthetic aperture radars with active phased array antennas

     Makhoul, Eduard; Broquetas Ibars, Antoni; Closa, Josep; Saameno, Paula
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2011-07-24
    Presentation of work at congresses

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    This paper proposes an analytical formulation of the instrumental errors in multilevel hierarchic SAR architecture equipped with active phased array antennas. The basis of the study is the derivation of the so called post-calibration errors, which remain as residual error contributions after the application of a dedicated internal calibration procedure. The limitations of the current internal calibration approaches for the-state-of-the-art space-borne SAR missions are analyzed and alternative internal global calibration strategies are proposed to reduce the impact of the post-calibration error. Numerical simulations of instrumental errors are presented to evaluate the different proposed calibration procedures.

  • Signal-to-noise ratio equalization for TOPSAR mode using a nonuniform steering rate

     Ruiz Rodon, Josep; Broquetas Ibars, Antoni; González Arbesú, José María; Closa Dominguez, Josep M.; Labriola, M
    IEEE Geoscience and Remote Sensing Letters
    Date of publication: 2011-09-15
    Journal article

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    In this letter, an optimized scanning in terrain observation by progressive scan synthetic aperture radar (TOPSAR) mode is studied. A nonuniform steering rate of the radar array antenna in the along-track direction is proposed in order to obtain constant radiometric sensitivity and signal-to-noise ratio. This is achieved owing to the longer integration time of the echoes received at both ends of the antenna azimuth sweep. By optimizing iteratively the array discrete steering rate law, the radiometric impact of the array basic element pattern (subarray pattern) can be accurately compensated. First, simulation results are presented to validate the nonuniform steering TOPSAR.

  • CONTRIBUTION OF ELASTIC-BACKSCATTER LIDARS TO WIND FIELD RETRIEVAL AND ATMOSPHERIC BOUNDARY LAYER MONITORING

     Tomas Martinez, Sergio
    Defense's date: 2011-12-15
    Department of Signal Theory and Communications, Universitat Politècnica de Catalunya
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  • On the design of microwave radiometers with digital beamforming and polarization synthesis for earth observation  Open access

     Bosch Lluis, Xavier
    Defense's date: 2011-03-30
    Department of Signal Theory and Communications, Universitat Politècnica de Catalunya
    Theses

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    Actualment, la comunitat científica ja disposa de les primeres mesures radiomètriques a banda L, polarimètriques i multi-angulars fetes de l’espai. Això és gràcies al recent llançament de la missió de la Eurepean Space Agency (ESA) anomenada Soil Moisture and Ocean Salinity (SMOS). Es sabut que a partir de la temperatura d’antena es possible recuperar salinitat superficial marina (Sea Surface Salinity, (SSS)) i humitat del sòl (Soil Moisture (SM)). Els beneficis de mesurar aquests dos paràmetres geofísics son múltiples, essent especialment profitosos en els camps de la oceanografia i la climatologia. La raó principal que va motivar la presentació del projecte Passive Advanced Unit (PAU) a la European Science Foundantion (ESF) va ser per estudiar la relació entre brillantor de temperatura i observables Global Navigation Satellite System Reflectometry (GNSS/R) per a millorar la recuperació de la SSS i SM. A més a més, els objectius tècnics del projecte PAU incloïen el desenvolupament de nous conceptes de radiòmetres en banda L, com a base tecnològica per a nous sistemes radiomètrics. La present tesi doctoral estén el coneixement adquirit en els últims anys en el desenvolupament del radiòmetre SMOS i és una contribució al desenvolupament d'una nova generació de sensors passius. Per primera vegada – pel que fa els coneixements de l'autor – s’ha desenvolupat amb èxit un radiòmetre amb una agrupació d’antenes capaç de formar feixos en temps real. Aquest sistema és capaç de dirigir múltiples i simultanis feixos en diferents angle d'incidència, sense cap m moviment mecànic, proporcionant així un nou mètode per a obtenir mesures multi-angulars. El projecte PAU ha estat desenvolupat en el Remote Sensing Lab, del Departament de Teoria del Senyal i Comunicacions de la Universitat Politècnica de Catalunya. La present tesi doctoral descriu la tasca realitzada entre 2005 i 2010, tant en aspectes teòrics i de hardware com en el camp de la radiometria de banda L. Aquesta tesi consisteix en un estudi teòric realitzat en radiòmetres correlació amb la formació de feix digital des del punt de vista dels radiòmetres d'obertura sintètica i una anàlisi exhaustiva del impacte del sistema de digitalització. D'altra banda, han estat definits els requisits per a construir un radiòmetre de correlació amb la formació de feix digital en temps real i amb síntesi de la polarització. Un instrument amb aquestes característiques s'ha construït, a nivell intern va igualar per l'amplitud i fase de cada receptor, provat i es caracteritza a la cambra anecoica, i, finalment, s’ha realitzat campanya de camp per obtenir valors de l'emissivitat del sòl per a una gamma d’angles d'incidència.

    With the recent launch of the ESA’s Soil Moisture and Ocean Salinity (SMOS) mission the scientific community is provided with the first polarimetric and multi-angular L-band radiometric measurements from the space. From the antenna temperature is possible to retrieve Sea Surface Salinity (SSS) and Soil Moisture (SM), which benefits both the oceanographic and climatologic studies. It is well known that it exists angular and polarization dependence for the radiometric measurements. Using this dependence, it is possible to use multi-angular and polarimetric measurements to retrieve geophysical parameters. The main rationale that motivated the submission of the Passive Advanced Unit (PAU) project to the European Science Foundation (ESF) was to study the relationship between the brightness temperatures and some Global Navigation Satellite System Reflectometry (GNSS/R) observables, so as to improve the SSS retrievals. Also, the technical objectives of the PAU project included the development of new L-band radiometer concepts, such as a technological bed for providing new radiometer systems. The present PhD dissertation extends the knowledge acquired in the recent years in the development of the SMOS radiometer, and is a contribution to the development of a new generation of passive sensors. For the first time – to author’s knowledge – real-time digital beamforming and polarization synthesis have been successfully implemented in a real system. The system is able to steer multiple and simultaneous beams in different incidence angles without mechanical scan of the antenna, providing a new method to obtain multi-angular measurements combining an L-band radiometer with the concept of digital beamformer. The PAU project has been developed by the Passive Remote Sensing Group of the Remote Sensing Lab, at the Department of Signal Theory and Communications of the Universitat Politècnica de Catalunya. The present PhD dissertation describes the work undertaken between 2005 and 2010 in both theoretical and hardware issues within the field of L-band radiometry with real-time digital beamforming with polarization synthesis. This dissertation consists of a theoretical study performed on digital correlation radiometers with beamforming from the point of view of the synthetic aperture radiometers and an extended analysis of the impact of the digitization scheme. Moreover, the requirements to build a correlation radiometer with real-time digital beamforming and polarization synthesis have been stated. The new concept instrument has been built, internally equalized for the amplitude and phase of each receiver, tested and characterized in the anechoic chamber, and in a field campaign obtaining soil emissivity values for a range of incidence angles.

  • Sistemas de teledetección activos y pasivos embarcados en sistemas aéreos no tripulados para la monitorización de la tierra  Open access

     Acevo Herrera, René
    Defense's date: 2011-04-04
    Department of Signal Theory and Communications, Universitat Politècnica de Catalunya
    Theses

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    La comunidad científica ha mostrado gran interés por estudiar los fenómenos que ocurren sobre la superficie de la tierra, específicamente los que suceden en la atmósfera, los océanos, o la superficie del suelo, y que afectan el clima o modifican la superficie de la tierra. Para poder analizar y predecir estos fenómenos, se monitorizan parámetros que se relacionan de manera directa o indirecta con procesos biofísicos y geofísicos. Es en este punto donde la teledetección entra en juego, puesto que es la técnica que permite medir tales parámetros de forma remota sin necesidad de entrar en contacto directo con un objeto o una superficie. En particular, la teledetección por microondas permite la detección de energía electromagnética casi bajo cualquier condición climática y a cualquier hora del día, debido a que a esta longitud de onda la energía electromagnética puede penetrar a través de las nubes, polvo, neblina y lluvia, y es menos susceptible a la dispersión atmosférica, que afecta en gran medida a las señales ópticas. Actualmente existen varios sistemas de teledetección por microondas que se han embarcado en satélites, para monitorizar parámetros biofísicos y geofísicos sobre la superficie de la tierra de manera global. También se han desarrollado estos sistemas para ser transportados en plataformas aéreas tripuladas para realizar estudios a nivel local o regional, donde se desea obtener información de una zona en particular en tiempos relativamente cortos. Sin embargo, ambas plataformas representan, entre otras cosas, un alto coste, no solo económico sino de infraestructura, equipo, grupos de trabajo, permisos de operación, y varios requerimientos más. El creciente desarrollo de los sistemas aéreos no tripulados (Unmanned Aerial Vehicle, UAV), ha hecho posible su uso para transportar sensores de teledetección. Los sistemas UAV presentan las mismas ventajas que los sistemas aéreos tripulados, pero además añaden otras ventajas adicionales. Por ejemplo, pueden ser operados durante varias horas de forma autónoma, el coste de explotación y desarrollo puede ser menor que el de un avión tripulado si se emplea un UAV de bajas prestaciones. Por tal motivo en este trabajo se propone el uso de un aeromodelo de control por radio como plataforma UAV para monitorizar diversos parámetros geofísicos y biofísicos de la tierra mediante sensores activos y pasivos de teledetección por microondas. Para realizar las medidas de teledetección pasiva se ha desarrollado el sensor denominado Airborne RadIometEr at L-Band (ARIEL) que es un radiómetro Dicke de bajo peso y pequeñas dimensiones, y que trabaja en Banda L (≈1.4 GHz). En la presenta memoria se muestra el diseño del sensor, las características principales de funcionamiento, y las técnicas de procesamiento de datos. Posteriormente se presentan las campañas de medida realizadas en zonas de cultivo, suelo descubierto, y zonas costeras. En tales campañas se han conseguido generar mapas de temperatura de brillo y de humedad de suelo. Con el fin de llevar a cabo medidas de teledetección activa se ha desarrollado el sistema denominado AiR Based REmote Sensing ARBRES, que consta de dos sensores radar de apertura sintética SAR diseñados a dos frecuencias diferentes, uno en Banda C (≈ 5.3 GHz) y otro en Banda X (≈ 9.65 GHz). Ambos radares son de onda continua FMCW, además son de bajo peso, bajo consumo de potencia y de pequeñas dimensiones. Ambos sensores tienen la capacidad de realizar medidas de interferometría SAR. En esta memoria se muestran las características de funcionamiento del sistema, así como algunos algoritmos de focalización de imágenes SAR, y una técnica para compensar los movimientos de la plataforma de vuelo. Finalmente se presentan medidas en campo para obtener imágenes de reflectividad de un escenario, y se muestran también los resultados para medidas realizadas en configuración de interferometría de simple pasada, la cual está relacionada con la topografía del terreno.

  • Research & Development of a Simulator for Moving Target Indicator System

     Makhoul Varona, Eduardo; Rius Casals, Juan-manuel; Aguasca Sole, Alberto; O'callaghan Castella, Juan Manuel; Broquetas Ibars, Antoni
    Participation in a competitive project

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  • Bistatic SAR based on Terrasar-X and ground based receivers

     Broquetas Ibars, Antoni; Fortes Galera, Eduardo M.; Siddique, M. A.; Duque, Sergi; Merlano Duncan, Juan Carlos; Lopez Dekker, Paco; Mallorqui Franquet, Jordi Joan; Aguasca Sole, Alberto
    IEEE International Geoscience and Remote Sensing Symposium
    Presentation's date: 2010-07-26
    Presentation of work at congresses

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  • Combined passive and active millimeter-wave imaging system for concealed objects detection

     Abril, Jordi; Nova, Enrique; Broquetas Ibars, Antoni; Torres Torres, Francisco; Romeu Robert, Jordi; Jofre Roca, Luis
    Infrared Millimeter and Terahertz Waves (IRMMW-THz), 2010 35th International Conference on
    Presentation's date: 2010-09-06
    Presentation of work at congresses

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  • Active and passive THz systems for short-range imaging applications

     Abril, Jordi; Nova, Enrique; Capdevila Cascante, Santiago; Broquetas Ibars, Antoni; Torres Torres, Francisco; Jofre Roca, Luis
    European Conference on Antennas and Propagation
    Presentation's date: 2010-04-13
    Presentation of work at congresses

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    Teraherz subsurface imaging system  Open access

     Nova, Enrique; Abril, Jordi; Guardiola Garcia, Marta; Capdevila Cascante, Santiago; Broquetas Ibars, Antoni; Romeu Robert, Jordi; Jofre Roca, Luis
    European Conference on Antennas and Propagation
    Presentation's date: 2010-04-12
    Presentation of work at congresses

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    A subsurface imaging system based on a terahertz time-domain spectrometer (THz-TDS) is described in this paper. The system performance has been simulated in terms of spatial resolution, penetration capabilities and SNR. Moreover, a commercial THz-TDS has been used to perform the proof-of-concept of the described system.

  • SABRINA-X: Bistatic SAR receiver for TerraSAR-X

     Broquetas Ibars, Antoni; Mallorqui Franquet, Jordi Joan; Aguasca Sole, Alberto; Merlano Duncan, Juan Carlos; Duque, Sergi
    European Conference on Synthetic Aperture Radar
    Presentation's date: 2010-06-09
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  • Far field condition in passive interferometry for security screening applications

     Torres Torres, Francisco; Abril, Jordi; Nova, E.; Broquetas Ibars, Antoni; Jofre Roca, Luis
    European Conference on Antennas and Propagation
    Presentation's date: 2010-04-12
    Presentation of work at congresses

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    This work presents the main geometric constraints that affect the performance of a passive interferometer at 94 GHz for security screening applications by means of a reviewed definition of the Far Field condition in close range detection applications. This new approach allows to easily give, in a first order approximation, the number of antennas, the array size and the target range by using well known far field tools.

  • Feasibility of geosynchronous satellites for synthetic aperture radar remote sensing at Ka-BAND

     Ruiz, Josep; González, Alba; Broquetas Ibars, Antoni; Monti Guarnieri, Andrea; Carcano, Laura; Fideli, Giorgio; Rocca, Fabbio
    Ka and Broadband Communications Navigation and Earth Observation Conference
    Presentation's date: 2010-10-20
    Presentation of work at congresses

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    This document presents the conceptual design and analysis of a Synthetic Aperture Radar (SAR) system based on geosynchronous satellites (GEOSAR) working at Ka-band. These satellites, apparently orbiting in a fixed position relative to the Earth, are affected by slight perturbations of the perfectly geostationary orbits (small inclinations and non zero eccentricities) that may be used to generate a synthetic aperture radar for Earth Observation. The main advantage of GEOSAR is to obtain short revisit pass (daily or less) with local coverage, thus complementary to typical Low Earth Orbit SAR that achieve global coverage but with weekly or monthly revisit times. A further advantage is the look direction, mainly South-North, that is truly complementary to the LEO satellites looking at East-West. The LEO long revisit times prevent the observation of fast dynamic scenarios like natural hazards, disasters, atmosphere, etc. The GEOSAR main characteristics are presented and different configurations are proposed. Some geosynchronous orbit considerations are shown to understand the particularities in the GEOSAR geometry. The compromises between spatial resolution and sensitivity are obtained together with basic operation parameters like Doppler Analysis, power link budget and ambiguities.

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    Measurement of the electromagnetic field backscattered by a fractal surface for the verification of electromagnetic scattering models  Open access

     Ruello, Giuseppe; Blanco Sanchez, Pablo; Iodice, Antonio; Mallorqui Franquet, Jordi Joan; Riccio, Daniele; Broquetas Ibars, Antoni; Franceschetti, Girogio
    IEEE transactions on geoscience and remote sensing
    Date of publication: 2010-04
    Journal article

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    Fractal geometry is widely accepted as an efficient theory for the characterization of natural surfaces; the opportunity of describing irregularity of natural surfaces in terms of few fractal parameters makes its use in direct and inverse electromagnetic (EM) scattering theories highly desirable. In this paper, we present an innovative procedure for manufacturing fractal surfaces and for measuring their scattering properties. A cardboard–aluminum fractal surface was built as a representation of a Weiestrass–Mandelbrot fractal process; the EM field scattered from it was measured in an anechoic chamber. A monostatic radarlike configuration was employed. Measurement results were compared to Kirchhoff approximation and small perturbation method closed-form results that were analytically obtained by employing the fractional Brownian motion to model the surface shape. Matching and discrepancies between theories andmeasurements are then discussed. Finally, fractal and classical surface models are compared as far as their use in the EM scattering is concerned.

  • Estudio de viabilidad de la estimación cuantitativa de parámetros de nieve mediante técnicas de teledetección (EOSWAN)

     Alonso Gonzalez, Alberto; Fabregas Canovas, Francisco Javier; Broquetas Ibars, Antoni; Mallorqui Franquet, Jordi Joan; López Martínez, Carlos
    Participation in a competitive project

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  • New European Watcher

     Rius Casals, Juan-manuel; O'callaghan Castella, Juan Manuel; Makhoul Varona, Eduardo; Broquetas Ibars, Antoni
    Participation in a competitive project

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  • Polarimetric differential SAR interferometru with ground-based sensors  Open access

     Pipia, Luca
    Defense's date: 2009-09-18
    Department of Signal Theory and Communications, Universitat Politècnica de Catalunya
    Theses

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    Las técnicas de Interferometría Diferencial se basan en la combinación de varias imágenes SAR con distinta separación temporal y permiten la recuperación de las componentes lineales y no-lineales del proceso de deformación ocurrida en el entorno de interés durante el entero periodo de observación. Condición imprescindible para una correcta estimación de los fenómenos geodéticos es la elevada estabilidad de la plataforma que embarca el sensor SAR. Por esta razón, a nivel operativo se utilizan datos SAR satelitales.El objetivo de la Polarimetría SAR es describir el entorno de interés analizando las propiedades de la señal que éste dispersa cuando se utilizan diferentes combinaciones de polarización de las antenas transmisora y receptora, definidas canales polarimétricos. La polarimetría interferométrica SAR junta la capacidad de la polarimetría de separar mecanismos de dispersión independientes con la sensibilidad de la Interferometría a la altura de los correspondientes centros de fase, y permite describir la distribución volumétrica de los dispersores dentro de la escena observada. Debido a la falta de conjuntos de datos polarimétricos SAR satelitales que cubran tramos temporales suficientemente largos, hay aún un gran interés en las mejoras que la polarimetría podría aportar a técnicas ya consolidadas como las de Interferometría Diferencial.La actividad de investigación que se presentará en esta tesis doctoral abarca, por primera vez conjuntamente, las dos áreas de la Polarimetría SAR y de la Interferometría Diferencial utilizando el sensor radar terrestre de corto alcance (gbSAR) desarrollado por la Universitat Politècnica de Catalunyua (UPC). El trabajo constará de dos bloques principales.El primer bloque describirá las técnicas que se han desarrollado para convertir el sistema UPC gbSAR en un instrumento operativo y simplificar la utilización de sus adquisiciones, incluyendo la formulación matemática de los principios de funcionamiento del sistema, la cadena de procesado de los raw data y su calibración polarimétrica, los procedimientos de georeferenciación, y las técnicas de compensación de los artefactos atmosféricos presentes en sus medidas diferenciales.La segunda parte se ocupará de demostrar los beneficios que los datos SAR polarimétricos ofrecen respecto a la medición de un único canal polarimétrico para aplicaciones diferenciales. A fin de llevar a cabo esta tarea, se analizarán los datos gbSAR adquiridos durante una campaña de medidas de un año realizada en el pueblo de Sallent, en Cataluña, afectado por un fenómeno de subsidencia. En esta parte se analizarán tres temas principales. El primero es el comportamiento no estacionario en tiempo del entorno urbano bajo la geometría de observación del sensor terrestre. Se estudiarán en detalle los efectos de su inestabilidad y se propondrá una técnica de filtrado novedosa entallada a las propiedades de los blancos deterministas con el fin de preservar la información de la fase diferencial. El segundo tema abarca el problema de los efectos de troposfera en datos diferenciales con separación temporal superior al mes y de su separación de las variaciones de fase inducidas por el proceso de deformación. El tercer tema es la utilización de toda la información polarimétrica diferencial. Con fin de superar las limitaciones propias de las técnicas DInSAR clásicas, se propondrá un nuevo modelo polarimétrico de dispersión y se demostrarán las ventajas de la nueva formulación enseñando la mejor estimación del proceso de subsidencia en Sallent. En la parte final de este apartado se explorará también el potencial de las técnicas polarimétricas de optimización de la coherencia para aplicaciones diferenciales.

    Differential SAR interferometry (DInSAR) deals with the combination of multi-temporal SAR images for the estimation of the linear and non-linear components of the deformation process within an area of interest during the whole observation period. A high stability of the platform is required for a reliable estimation of the geodetic phenomena. Accordingly, space-borne SAR images are operatively employed for DInSAR estimation, air-borne DInSAR still constituting a challenging research issue. SARPolarimetry aims at charactering the illuminated area through the analysis of its response under different combinations of transmitting and receiving antennas polarization, called polarimetric channels. The Polarimetric SAR Interferometry joins the capability of Polarimetry to separate independent scattering mechanisms and the sensitivity of Interferometry to the corresponding phase centers' elevation, making it possible to describe the volumetric distribution of the scatterers within the observed area. Owing to the lack of long-time collections of polarimetric space-borne SAR data, the studies carried out in this research field have been mainly based on air-borne acquisitions. Yet, there is a great expectation for the improvements that polarimetry may bring to assessed single-polarization techniques such as the DinSAR.The research described in this PhD dissertation fills for the first time the gap between SAR Polarimetry and SAR Differential Interferometry through the employment of an X-band ground-based SAR (gbSAR) sensor developed by the Remote Sensing Lab of the Universitat Politècnica de Catalunya (UPC).The work is divided into two main blocks. The first part deals with the algorithms that have been developed to make the UPC system operative and its acquisitions easy to use. Summarily, they include the mathematical formulation of the sensor's working principles, the raw data processing chain and the polarimetric calibration method, the geocoding procedures, and the techniques compensating for the atmospheric artefacts affecting gbSAR zero-baseline acquisitions.The second part is concerned with demonstrating the benefits that polarimetric SAR measurements provide with respect to single-polarization data for differential applications. In order to cope with this task, the data sets acquired during a one-year measurement campaign carried out in the village of Sallent, northeastern Spain, are analyzed. The experiment was focused on monitoring the subsidence phenomenon affecting a district of the village with the UPC gbSAR sensor. Three main issues are here argued. The first one is the time non-stationary behaviors characterizing the urban environment at X-band in the gbSAR observation geometry. Their effects are analyzed in detail and a novel non-stationary filtering technique tailored to deterministic scatterers' properties is introduced to preserve the differential phase information. The second one is the compensation of the troposphere changes in long-time span gbSAR differential interferograms. A new technique is worked out to effectively separate the differential phase variations due to the atmospheric artefacts from the deformation components. The third one is the use of the whole polarimetric differential information. A novel polarimetric differential scattering model is put forward to relax the constraints of an advanced DInSAR technique, the Coherent Pixel Technique, and to propose an innovative polarimetric approach. The advantages offered by Polarimetric DInSAR are demonstrated in terms of quality of the deformation-rate map describing the subsidence phenomenon in Sallent. In the end, the potentials of coherence-optimization techniques for the further improvement of the deformation process estimation are stressed.

  • BLOCKSAT-2: GUIADO Y POSICIONAMIENTO DE TRÁFICO FERROVIARIO CON SEGURIDAD INTRÍNSECA: SISTEMA DE BLOQUEO BASADO EN NAVEGACIÓN X SATÉ

     Comeron Tejero, Adolfo; Gelonch Bosch, Antoni; Jofre Roca, Luis; Romeu Robert, Jordi; Fuertes Armengol, José Mª; Cabestany Moncusi, Joan; Broquetas Ibars, Antoni
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  • CONCEPTOS AVANZADOS EN TELEDETECCION ACTIVA Y PASIVA DE MICROONDAS: TECNOLOGIA Y APLICACIONES

     Corbella Sanahuja, Ignasi; Torres Torres, Francisco; Broquetas Ibars, Antoni; Mallorqui Franquet, Jordi Joan; Duffo Ubeda, Nuria; Aguasca Sole, Alberto; López Martínez, Carlos; Fabregas Canovas, Francisco Javier
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  • UWB Tomographic Radar Imaging of Penetrable and Impenetrable Objects

     Jofre Roca, Luis; Broquetas Ibars, Antoni; Romeu Robert, Jordi; Blanch Boris, Sebastian; Toda, Ap; Fabregas Canovas, Francisco Javier
    Proceedings of the IEEE
    Date of publication: 2009-02
    Journal article

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  • Bistatic interferometry using fixed receiver configurations

     Duque Biarge, Sergio; Lopez Dekker, Paco; Merlano Duncan, Juan Carlos; Mallorqui Franquet, Jordi Joan; Broquetas Ibars, Antoni
    European Conference on Synthetic Aperture Radar
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  • Marine applications of SAR polarimetry  Open access  awarded activity

     Margarit Martin, Gerard
    Defense's date: 2007-07-11
    Department of Signal Theory and Communications, Universitat Politècnica de Catalunya
    Theses

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    Els oceans mantenen una fràgil i complexa cadena que enllaça un alt nombre de factors biològics, sociològics i econòmics. Actualment, aquest ecosistema està amenaçat per l'activitat humana i uns dels punts més crítics és la sobreexplotació pesquera. Això ha despertat la consciencia de les autoritats d'arreu per a protegir l'entorn marí i assegurar, així, la seguretat i supervivència dels éssers humans. Tal objectiu demana el desenvolupament de polítiques de control que monitorin l'activitat dels vaixells. Fins l'actualitat, diferents propostes s'han estudiat per monitorar vaixells, com per exemple transpondedors, teledetecció òptica i sensors acústics passius. L'experiència en entorns reals ha demostrat que cap d'aquestes solucions és eficient. Una alternativa poden ser els Radars d'Obertura Sintètica (SAR). Aquests sistemes utilitzen les propietats de reflectivitat i dispersió dels vaixells per identificar-los amb independència de qualsevol fenomen atmosfèric i del cicle dia/nit. El sensors SAR sintetitzen una obertura més gran que la real permetent l'obtenció d'imatges de reflectivitat d'uns quants kilòmetres d'amplada amb una resolució de pocs metres.En la monitorització de vaixells, la tecnologia SAR ha demostrat unes bones prestacions per la detecció. Treu profit del fet que els vaixells dispersen més energia que el mar i, així, apareixen en les imatges com punts molt brillants. Però, la seva utilitat en la identificació de vaixells encara no està clara. Hi ha dues limitacions importants: 1) les resolucions dels sistemes actuals no semblen suficients per aïllar característiques geomètriques a partir de la informació de reflectivitat i 2) les distorsions que les signatures dels vaixells experimenten en entorns marins. Aquests problemes es poden resoldre parcialment si s'utilitzen dades SAR multidimensional. Aquest concepte es refereix al fet d'adquirir imatges SAR modificant un o més paràmetres del sistema. En la classificació de vaixells, hi ha dues opcions clares: 1) Polarimetria SAR (PolSAR) que utilitza les dues components polarimètriques de l'ona EM i 2) la Interferometria SAR que s'obté per la combinació de dues imatges SAR adquirides des de posicions molt properes. Per a una banda, la polarització de l'ona EM és una propietat intrínseca de l'ona que ajuda a aïllar estructures geomètriques particulars per mitjà de la teoria de descomposició de blancs (TD). Per l'altra, la interferometria treu profit de la diferencia de fase entre les dues imatges SAR per obtenir la tercera dimensió de l'escena.PolSAR and InSAR presenten grans possibilitats per la monitorització de vaixells ja que poden solucionar algunes de les limitacions dels mètodes clàssics. Desafortunadament, encara no han estat profundament estudiades a causa de les dificultats en obtenir dades reals validades. Això ha limitat el nombre d'estudis en aquesta temàtica. En aquest entorn, la tesi està orientada a avaluar fins a quin punt les tècniques PolSAR i InSAR poden ser útils per la monitorització de vaixells. Per a tal propòsit, s'han fixat quatre objectius importants:1. El desenvolupament d'un simulador SAR eficient que doni imatges realistes de vaixells i que solucioni el dèficit de dades reals en entorns marins.2. L'estudi de la dispersió dels vaixells que fixi els principals mecanismes de dispersió observats en imatges SAR i com es relacionen amb la geometria dels vaixells. 3. Un estudi de les prestacions de les tècniques actuals d'anàlisis de dades PolSAR en la classificació de vaixells.4. El desenvolupament d'un mètode nou i eficient per la identificació de vaixells.Al llarg de la tesis, els diferents punts seran estudiats i resolts. El desenvolupament de GRECOSAR, un simulador SAR de blancs complexes que dóna imatges de vaixells similars a les adquirides en entorns reals, ha estat essencial per estudiar les propietats de dispersió dels vaixells. Ha permès demostrar que els vaixells es poden distingir a partir del seu patró dispersiu, el qual és senzill i dominat per alguns dispersors guia que presenten una marcada estabilitat i potència de dispersió. Amb aquests resultats ha estat possible desenvolupar un nou mètode que pot identificar vaixells sota condicions d'observació adverses. Combina característiques polarimètriques i interferomètriques SAR (PolInSAR) per inferir estimacions 3D de la geometria dels vaixells. Diferents tests han demostrat que aquest mètode dóna una millor fiabilitat en la identificació que altres mètodes actualment disponibles. Malgrat tot, fixa uns requeriments tecnològics més elevats, sobretot en la resolució de les imatges i en les característiques PolInSAR. La nova generació de sensors SAR els poden cobrir.

    Oceans support a complex and fragile chain that links a high number of biological, sociological and economical factors. In these days, this ecosystem is endangered by human activity and one of the main hot spots is overfishing. As a result, authorities worldwide have become aware about the necessity to law-protect the marine environment in order to assure the safety and sustenance of human beings. This demands the development of fisheries policy to monitor the activities of ships.Up to now, different vessel monitoring proposals have been considered, for instance transponders, optical remote sensing or passive acoustic sensors. The lessons learnt in real scenarios have shown that none of these solutions is efficient. A feasible option may be the so-called active Synthetic Aperture Radar (SAR) technology. It uses the reflectivity/scattering properties of vessels for basing the identification process with independence of any atmospheric phenomena and day/night cycle. SAR sensors synthesize an antenna aperture larger than the real one and this allows to acquire reflectivity images of some tens of kilometers wide with a resolution of few meters.In vessel monitoring, SAR imagery has proven good performance for vessel detection. They take profit of the fact that vessels normally backscatter more power than the sea and, hence, they appear in the images as bright spots. But their usefulness in vessel identification has not been established yet. There are two main limitations, namely: 1) the resolution of current systems that appears to be not enough for isolating geometrical features from the reflectivity information of SAR images and 2) the distortions that vessel' signatures experiment within sea scenarios. Such problems can be solved up to certain extend if multidimensional SAR data is used. This concept refers to the possibility to acquire different SAR images by modifying one or more imaging parameters. In the scope of vessel classification, there are two main options, namely: 1) SAR polarimetry (PolSAR) that refers to the usage of the two polarimetric components of the EM wave and 2) SAR interferometry (InSAR) derived by combining two SAR images acquired from slightly different positions. On the one hand, the polarization of an EM wave is an intrinsic wave property that helps on identifying specific geometrical structures via Target Decomposition (TD) theory. On the other hand, Interferometry takes profit of the phase difference between the two SAR images to retrieve the third dimension of the scene.PolSAR and InSAR have great potentialities for supporting vessel monitoring as they can overcome some of the limitations of classical methods. Unfortunately, they have not been exploited yet due to the difficulties on having at one's disposal real data with reliable ground-truth. This has limited the number of works tackling such issue. In this framework, the current thesis is focused to evaluate up to which extend PolSAR and InSAR imagery are reliable for vessel monitoring. For such purpose, four main goals are proposed, namely:1. The development of an efficient SAR simulation environment that provides realistic vessel SAR images and overcomes the current data deficiency related to marine scenarios.2. The study of vessel scattering to fix the main polarimetric scattering mechanisms observed in vessel SAR images and how they are related with the geometries of vessels.3. A performance study of current analysis tools of PolSAR data in vessel classification.4. The development of a novel and efficient methodology for vessel identification.Along the thesis, the different points are studied and solved. The development of GRECOSAR, a SAR simulator of complex targets able to provide vessel images similar to those obtained in real scenarios, has been essential for studying the scattering properties of vessels. It has allowed to show that vessels can be distinguished by means of their scattering pattern, which appear to be not so complex and dominated by some guide scatters that present a marked reflectivity stability and scattered power. With these results, a new approach able to identify vessels even under adverse observation conditions has been developed. It combines polarimetric and interferometric SAR (PolInSAR) capabilities to retrieve 3D estimates of the geometry of ships. Different tests have shown that the proposed method provides better identification confidence than other available methods. However, it demands higher technological requirements in terms of image resolution and PolInSAR features. The new generation of SAR sensors may fulfill them.

  • European Master of Research on Information and Communication Technologies

     Broquetas Ibars, Antoni
    MSc Seminar (Masters Europeus) organitzat pel CLUSTER
    Presentation's date: 2006-05-19
    Presentation of work at congresses

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  • Synthesis, construction and validation of a fractal surface

     Ruello, G; Blanco, P; Iodice, A; Mallorqui Franquet, Jordi Joan; Riccio, D; Broquetas Ibars, Antoni; Franceschetti, G
    IEEE transactions on geoscience and remote sensing
    Date of publication: 2006-06
    Journal article

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  • European Master of Research on Information and Communication Technologies

     Broquetas Ibars, Antoni
    MSc Seminar (Masters Europeus) organitzat pel CLUSTER
    Presentation of work at congresses

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  • Performance Study of Quantized Linear Frequency Modulated signals and its application to CW radars

     Aguasca Sole, Alberto; Broquetas Ibars, Antoni
    3rd European Radar Conference
    Presentation of work at congresses

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