Articles de revista
http://hdl.handle.net/2117/1443
20170117T15:24:32Z

Generation of atmospheric wavefronts using binary micromirror arrays
http://hdl.handle.net/2117/98622
Generation of atmospheric wavefronts using binary micromirror arrays
Anzuola, Esdras; Belmonte Molina, Aniceto
To simulate in the laboratory the influence that a turbulent atmosphere has on light beams, we introduce a practical method for generating atmospheric wavefront distortions that considers digital holographic reconstruction using a programmable binary micromirror array. We analyze the efficiency of the approach for different configurations of the micromirror array and experimentally demonstrate the benchtop technique. Though the mirrors on the digital array can only be positioned in one of two states, we show that the holographic technique can be used to devise a wide variety of atmospheric wavefront aberrations in a controllable and predictable way for a fraction of the cost of phaseonly spatial light modulators.
© 2016 [2016 Optical Society of America.]. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modifications of the content of this paper are prohibited.
20161220T12:35:19Z
Anzuola, Esdras
Belmonte Molina, Aniceto
To simulate in the laboratory the influence that a turbulent atmosphere has on light beams, we introduce a practical method for generating atmospheric wavefront distortions that considers digital holographic reconstruction using a programmable binary micromirror array. We analyze the efficiency of the approach for different configurations of the micromirror array and experimentally demonstrate the benchtop technique. Though the mirrors on the digital array can only be positioned in one of two states, we show that the holographic technique can be used to devise a wide variety of atmospheric wavefront aberrations in a controllable and predictable way for a fraction of the cost of phaseonly spatial light modulators.

The curious arithmetic of optical vortices
http://hdl.handle.net/2117/98471
The curious arithmetic of optical vortices
Molina Terriza, Gabriel; Recolons Martos, Jaume; Torner Sabata, Lluís
The superposition of noncoaxial light beams containing screw wavefront dislocations is shown to create light patterns with a richer vortex content than that given by the arithmetic of the topological charges of the individual beams. We report the experimental observation of this phenomenon.
© 2000 Optical Society of America
20161216T14:25:57Z
Molina Terriza, Gabriel
Recolons Martos, Jaume
Torner Sabata, Lluís
The superposition of noncoaxial light beams containing screw wavefront dislocations is shown to create light patterns with a richer vortex content than that given by the arithmetic of the topological charges of the individual beams. We report the experimental observation of this phenomenon.
© 2000 Optical Society of America

From field experiments to salinity products: a tribute to the contributions of Jordi Font to the SMOS mission
http://hdl.handle.net/2117/98458
From field experiments to salinity products: a tribute to the contributions of Jordi Font to the SMOS mission
Camps Carmona, Adriano José; Gabarró Prats, Carolina; VallLlossera Ferran, Mercedes Magdalena; Blanch Boris, Sebastián; Aguasca Solé, Alberto; Torres Torres, Francisco; Corbella Sanahuja, Ignasi; Duffo Ubeda, Núria; Turiel Martínez, Antonio; Portabella, Marcos; Ballabrera Poy, Joaquim; González Gambau, V.; Martinez, Justino; Villarino Villarino, Ramon; Monerris Belda, Sandra; Bosch Lluis, Xavier; Sabia, Roberto; Talone, Marco; Piles Guillem, Maria; Pablos Hernánez, Miriam; Valencia Domenech, Enric
This article summarizes some of the activities in which Jordi Font, research professor and head of the Department of Physical and Technological Oceanography, Institut de Ciències del Mar (CSIC, Spanish National Research Council) in Barcelona, has been involved as coPrincipal Investigator for Ocean Salinity of the European Space Agency Soil Moisture and Ocean Salinity (SMOS) Earth Explorer Mission from the perspective of the Remote Sensing Lab at the Universitat Politècnica de Catalunya. We have probably left out some of his many contributions to salinity remote sensing, but we hope that this review will give an idea of the importance of his work. We focus on the following issues: 1) the new accurate measurements of the sea water dielectric constant, 2) the WISE and EuroSTARRS field experiments that helped to define the geophysical model function relating brightness temperature to sea state, 3) the FROG 2003 field experiment that helped to understand the emission of sea foam, 4) GNSSR techniques for improving sea surface salinity retrieval, 5) instrument characterization campaigns, and 6) the operational implementation of the Processing Centre of Levels 3 and 4 at the SMOS Barcelona Expert Centre.
20161216T11:23:29Z
Camps Carmona, Adriano José
Gabarró Prats, Carolina
VallLlossera Ferran, Mercedes Magdalena
Blanch Boris, Sebastián
Aguasca Solé, Alberto
Torres Torres, Francisco
Corbella Sanahuja, Ignasi
Duffo Ubeda, Núria
Turiel Martínez, Antonio
Portabella, Marcos
Ballabrera Poy, Joaquim
González Gambau, V.
Martinez, Justino
Villarino Villarino, Ramon
Monerris Belda, Sandra
Bosch Lluis, Xavier
Sabia, Roberto
Talone, Marco
Piles Guillem, Maria
Pablos Hernánez, Miriam
Valencia Domenech, Enric
This article summarizes some of the activities in which Jordi Font, research professor and head of the Department of Physical and Technological Oceanography, Institut de Ciències del Mar (CSIC, Spanish National Research Council) in Barcelona, has been involved as coPrincipal Investigator for Ocean Salinity of the European Space Agency Soil Moisture and Ocean Salinity (SMOS) Earth Explorer Mission from the perspective of the Remote Sensing Lab at the Universitat Politècnica de Catalunya. We have probably left out some of his many contributions to salinity remote sensing, but we hope that this review will give an idea of the importance of his work. We focus on the following issues: 1) the new accurate measurements of the sea water dielectric constant, 2) the WISE and EuroSTARRS field experiments that helped to define the geophysical model function relating brightness temperature to sea state, 3) the FROG 2003 field experiment that helped to understand the emission of sea foam, 4) GNSSR techniques for improving sea surface salinity retrieval, 5) instrument characterization campaigns, and 6) the operational implementation of the Processing Centre of Levels 3 and 4 at the SMOS Barcelona Expert Centre.

Remote sensing of hydrometeors by means of interfermotric radiometry: theory and experimental results
http://hdl.handle.net/2117/98393
Remote sensing of hydrometeors by means of interfermotric radiometry: theory and experimental results
Bará Temes, Francisco Javier; Corbella Sanahuja, Ignasi; Torres Torres, Francisco; Camps Carmona, Adriano José; Martín Neira, Manuel; Nesti, G; Olhmer, E
Spaceborne and groundbased radiometric measurements at microwave and millimeterwave frequencies have proved able to monitor hydrometeors, but at present the angular resolution of those systems is limited by the radiometer's antenna beam width. Efforts to improve the angular resolution of such systems by applying the interferometric techniques successfully used in radio astronomy [Thompson et al, 1986; Ruf et al., 1988] have encountered two main limitations. First, imaging interferometric radiometers are extremely complex, with a very large number of antennas and correlators. Second, because of the wide field of view, the array size is restricted by spatial decorrelation effects that cannot be simply compensated for by an adjustable delay, as in radio astronomy. Bandwidth segmentation overcomes this limitation at the expense of an even higher system's complexity. To overcome these limitations, this paper presents a technique that may achieve high angular resolution with a minimum number of antennas, taking advantage of the spatial filtering due to signal decorrelation. It describes both the basic theory behind this process and the experimental results at X band with a random static distribution of rubber bits and with simulated rain. The experimental results agree well with theoretical predictions and computer simulations, showing the inevitable tradeoff between angular resolution and radiometric sensitivity.
20161215T18:11:32Z
Bará Temes, Francisco Javier
Corbella Sanahuja, Ignasi
Torres Torres, Francisco
Camps Carmona, Adriano José
Martín Neira, Manuel
Nesti, G
Olhmer, E
Spaceborne and groundbased radiometric measurements at microwave and millimeterwave frequencies have proved able to monitor hydrometeors, but at present the angular resolution of those systems is limited by the radiometer's antenna beam width. Efforts to improve the angular resolution of such systems by applying the interferometric techniques successfully used in radio astronomy [Thompson et al, 1986; Ruf et al., 1988] have encountered two main limitations. First, imaging interferometric radiometers are extremely complex, with a very large number of antennas and correlators. Second, because of the wide field of view, the array size is restricted by spatial decorrelation effects that cannot be simply compensated for by an adjustable delay, as in radio astronomy. Bandwidth segmentation overcomes this limitation at the expense of an even higher system's complexity. To overcome these limitations, this paper presents a technique that may achieve high angular resolution with a minimum number of antennas, taking advantage of the spatial filtering due to signal decorrelation. It describes both the basic theory behind this process and the experimental results at X band with a random static distribution of rubber bits and with simulated rain. The experimental results agree well with theoretical predictions and computer simulations, showing the inevitable tradeoff between angular resolution and radiometric sensitivity.

Design of single shaped reflector antennas for synthesis of shaped contour beams using genetic algorithms
http://hdl.handle.net/2117/98391
Design of single shaped reflector antennas for synthesis of shaped contour beams using genetic algorithms
VallLlossera Ferran, Mercedes Magdalena; Rius Casals, Juan Manuel; Duffo Ubeda, Núria; Cardama Aznar, Ángel
A genetic algorithm (GA) has been developed for designing singleshaped reflector antennas for the synthesis of shaped contour beams. The graphical processing technique is used in order to obtain the antenna radiation patterns very efficiently. Results comparing with the classical conjugate gradient are included to provide validation. © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 27: 358–361, 2000.
20161215T18:07:57Z
VallLlossera Ferran, Mercedes Magdalena
Rius Casals, Juan Manuel
Duffo Ubeda, Núria
Cardama Aznar, Ángel
A genetic algorithm (GA) has been developed for designing singleshaped reflector antennas for the synthesis of shaped contour beams. The graphical processing technique is used in order to obtain the antenna radiation patterns very efficiently. Results comparing with the classical conjugate gradient are included to provide validation. © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 27: 358–361, 2000.

Generalized transverse resonance analysis of planar discontinuities considering the edge effect
http://hdl.handle.net/2117/98370
Generalized transverse resonance analysis of planar discontinuities considering the edge effect
Barlabe Dalmau, Antoni; Comerón Tejero, Adolfo; Pradell i Cara, Lluís
Abstract:
Modematching related techniques such as the Generalized Transverse Resonance Method (GTR) suffer from the relative convergence phenomenon. To reduce its influence, we present a technique consisting of the application of basis functions incorporating the singular behavior of fields at edges and an optimal modal ratio. We present the results obtained analyzing a uniform finline and a shortcircuited finline which demonstrate the minimization of the relative convergence phenomenon, allowing a fast and accurate analysis on a lowcost personal computer.
20161215T15:42:37Z
Barlabe Dalmau, Antoni
Comerón Tejero, Adolfo
Pradell i Cara, Lluís
Abstract:
Modematching related techniques such as the Generalized Transverse Resonance Method (GTR) suffer from the relative convergence phenomenon. To reduce its influence, we present a technique consisting of the application of basis functions incorporating the singular behavior of fields at edges and an optimal modal ratio. We present the results obtained analyzing a uniform finline and a shortcircuited finline which demonstrate the minimization of the relative convergence phenomenon, allowing a fast and accurate analysis on a lowcost personal computer.

The correlation of visibility noise and its impact on the radiometric resolution of an aperture synthesis radiometer
http://hdl.handle.net/2117/98365
The correlation of visibility noise and its impact on the radiometric resolution of an aperture synthesis radiometer
Bará Temes, Francisco Javier; Camps Carmona, Adriano José; Torres Torres, Francisco; Corbella Sanahuja, Ignasi
The correlation between the visibility samples' noise of an aperture synthesis radiometer are required for the computation of the recovered temperature noise of a given pixel and of the improvement introduced by baseline redundance. A general expression for this correlation and noise examples for a linear array are presented.
20161215T15:28:02Z
Bará Temes, Francisco Javier
Camps Carmona, Adriano José
Torres Torres, Francisco
Corbella Sanahuja, Ignasi
The correlation between the visibility samples' noise of an aperture synthesis radiometer are required for the computation of the recovered temperature noise of a given pixel and of the improvement introduced by baseline redundance. A general expression for this correlation and noise examples for a linear array are presented.

Analisys of noise injection networks for interferometric radiometer calibration
http://hdl.handle.net/2117/98362
Analisys of noise injection networks for interferometric radiometer calibration
Corbella Sanahuja, Ignasi; Camps Carmona, Adriano José; Torres Torres, Francisco; Bará Temes, Francisco Javier
Abstract:
The spatial resolution of current spaceborne Earth observation radiometers is limited by the physical antenna aperture. This is especially critical at Lband, which exhibits high sensitivity to soil moisture and sea surface salinity. Interferometric radiometers (InR's) are currently being studied by several space agencies as a feasible alternative to overcome this problem. However, their calibration is a crucial issue since most techniques inherited from radio astronomy cannot be directly applied. Due to the large number of receiving channels, calibration techniques based on centralized noise injection from a single noise source will require a large and stable distribution network, which is technically very complex and unacceptable from the pointofview of mass and volume. Procedures based on distributed noise injection from a set of noise sources through smaller distribution networks have been recently proposed by the authors as an alternative to alleviate these technological problems. In this paper, the analysis of these networks, the impact of the noise generated by the network losses on the calibration, and the impact of frontend reradiated noise are analyzed. Finally, the optimum circuit topologies and tolerances to which these networks have to be characterized in order to achieve the required calibration are derived. These configurations are formed by cascading basic 1:2 and 1:3 isolated power splitters. Isolators at receiver inputs have to be included in order to minimize offsets originating from the correlation of reradiation of receiver noise. It has been found that, in order to satisfy the calibration requirements of InR's, the Sparameters of the ensemble noiseinjection network plus isolators have to be known to within 0.0250.050 dB in amplitude and 0.5/spl deg/ in phase, and their physical temperature known to within 0.5/spl deg/C.
20161215T15:13:31Z
Corbella Sanahuja, Ignasi
Camps Carmona, Adriano José
Torres Torres, Francisco
Bará Temes, Francisco Javier
Abstract:
The spatial resolution of current spaceborne Earth observation radiometers is limited by the physical antenna aperture. This is especially critical at Lband, which exhibits high sensitivity to soil moisture and sea surface salinity. Interferometric radiometers (InR's) are currently being studied by several space agencies as a feasible alternative to overcome this problem. However, their calibration is a crucial issue since most techniques inherited from radio astronomy cannot be directly applied. Due to the large number of receiving channels, calibration techniques based on centralized noise injection from a single noise source will require a large and stable distribution network, which is technically very complex and unacceptable from the pointofview of mass and volume. Procedures based on distributed noise injection from a set of noise sources through smaller distribution networks have been recently proposed by the authors as an alternative to alleviate these technological problems. In this paper, the analysis of these networks, the impact of the noise generated by the network losses on the calibration, and the impact of frontend reradiated noise are analyzed. Finally, the optimum circuit topologies and tolerances to which these networks have to be characterized in order to achieve the required calibration are derived. These configurations are formed by cascading basic 1:2 and 1:3 isolated power splitters. Isolators at receiver inputs have to be included in order to minimize offsets originating from the correlation of reradiation of receiver noise. It has been found that, in order to satisfy the calibration requirements of InR's, the Sparameters of the ensemble noiseinjection network plus isolators have to be known to within 0.0250.050 dB in amplitude and 0.5/spl deg/ in phase, and their physical temperature known to within 0.5/spl deg/C.

Infrared thermograms applied to nearfield testing
http://hdl.handle.net/2117/98358
Infrared thermograms applied to nearfield testing
González, J.M.; Aguasca Solé, Alberto; Romeu Robert, Jordi
Electromagnetic fields close to radiant structures can be measured quickly using an infrared camera. Examples of induced fields by wire antennas over a detection screen at distances shorter than one wavelength are presented. The measured thermograms agree with simulations that take into account heat propagation on the detection screen
20161215T14:57:20Z
González, J.M.
Aguasca Solé, Alberto
Romeu Robert, Jordi
Electromagnetic fields close to radiant structures can be measured quickly using an infrared camera. Examples of induced fields by wire antennas over a detection screen at distances shorter than one wavelength are presented. The measured thermograms agree with simulations that take into account heat propagation on the detection screen

Numerical simulation of long path spherical wave propagation in threedimensional random media
http://hdl.handle.net/2117/98348
Numerical simulation of long path spherical wave propagation in threedimensional random media
Fernández Rubio, Juan Antonio; Belmonte Molina, Aniceto; Comerón Tejero, Adolfo
A new method to overcome some limitations in the simulation of the propagation of waves originating from a point source through a very long path in a turbulent medium is presented. Existing propagation simulation algorithms suffer from either windowing or lack of resolution when applied to long paths. If Cartesian coordinates are used, the limited size of the numerical mesh eventually leads to windowing errors. Casting the classical splitstep Fourier algorithm in a spherically diverging coordinate system allows one to get around this problem. In this way an angular mesh matching the source and the propagation algorithm to the problem geometry is used. But for longpath propagation, this spherical divergent mesh causes a loss of resolution that can become a serious problem in the evaluation of the field statistical moments. The method discussed in this paper overcomes both the windowing effect associated with Cartesian coordinates and the loss of resolution accompanying spherical coordinates by using a sphericalcoordinate algorithm and performing repeated interpolations of the numerically propagated field before the mesh grows too large to sample the field accurately. Each time an interpolation is done, the angular window is decreased to maintain the matrix size. © 1999 Society of PhotoOptical Instrumentation Engineers.
20161215T14:19:02Z
Fernández Rubio, Juan Antonio
Belmonte Molina, Aniceto
Comerón Tejero, Adolfo
A new method to overcome some limitations in the simulation of the propagation of waves originating from a point source through a very long path in a turbulent medium is presented. Existing propagation simulation algorithms suffer from either windowing or lack of resolution when applied to long paths. If Cartesian coordinates are used, the limited size of the numerical mesh eventually leads to windowing errors. Casting the classical splitstep Fourier algorithm in a spherically diverging coordinate system allows one to get around this problem. In this way an angular mesh matching the source and the propagation algorithm to the problem geometry is used. But for longpath propagation, this spherical divergent mesh causes a loss of resolution that can become a serious problem in the evaluation of the field statistical moments. The method discussed in this paper overcomes both the windowing effect associated with Cartesian coordinates and the loss of resolution accompanying spherical coordinates by using a sphericalcoordinate algorithm and performing repeated interpolations of the numerically propagated field before the mesh grows too large to sample the field accurately. Each time an interpolation is done, the angular window is decreased to maintain the matrix size. © 1999 Society of PhotoOptical Instrumentation Engineers.