Articles de revista
http://hdl.handle.net/2117/658
20171124T22:36:43Z

Versatile and accurate schemes of discretization in the scattering analysis of 2D composite objects with penetrable or perfectly conducting regions
http://hdl.handle.net/2117/107764
Versatile and accurate schemes of discretization in the scattering analysis of 2D composite objects with penetrable or perfectly conducting regions
Sekulic, Ivan; Úbeda Farré, Eduard; Rius Casals, Juan Manuel
The methodofmoment discretization of boundary integral equations in the scattering analysis of closed infinitely long (2D) objects, perfectly conducting (PEC) or penetrable, is traditionally carried out with continuous piecewise linear basis functions, which embrace pairs of adjacent segments. This is numerically advantageous because the discretization of the transversal component of the scattered fields, electric (TE) or magnetic (TM), becomes free from hypersingular Kernel contributions. In the analysis of composite objects, though, the imposition of the continuity requirement around junction nodes, where the boundaries of several regions intersect, becomes especially awkward. In this paper, we present, for the scattering analysis of composite objects, a new combined discretization of the Poggio–Miller–Chang–Harrington–Wu–Tsai (PMCHWT) integral equation, for homogeneous dielectric regions, and the electricfield integral equation, for PEC regions, such that the basis functions are defined strictly on each segment, with no continuity constraint between adjacent segments. We show the improved observed accuracy with the proposed TEPMCHWT implementation on several dielectric objects with sharp edges and corners and moderate or high contrasts. Furthermore, we illustrate the versatility of these schemes in the analysis of 2D composite piecewise homogeneous objects without sacrificing accuracy with respect to the conventional implementations.
©2017 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.
20170919T10:44:02Z
Sekulic, Ivan
Úbeda Farré, Eduard
Rius Casals, Juan Manuel
The methodofmoment discretization of boundary integral equations in the scattering analysis of closed infinitely long (2D) objects, perfectly conducting (PEC) or penetrable, is traditionally carried out with continuous piecewise linear basis functions, which embrace pairs of adjacent segments. This is numerically advantageous because the discretization of the transversal component of the scattered fields, electric (TE) or magnetic (TM), becomes free from hypersingular Kernel contributions. In the analysis of composite objects, though, the imposition of the continuity requirement around junction nodes, where the boundaries of several regions intersect, becomes especially awkward. In this paper, we present, for the scattering analysis of composite objects, a new combined discretization of the Poggio–Miller–Chang–Harrington–Wu–Tsai (PMCHWT) integral equation, for homogeneous dielectric regions, and the electricfield integral equation, for PEC regions, such that the basis functions are defined strictly on each segment, with no continuity constraint between adjacent segments. We show the improved observed accuracy with the proposed TEPMCHWT implementation on several dielectric objects with sharp edges and corners and moderate or high contrasts. Furthermore, we illustrate the versatility of these schemes in the analysis of 2D composite piecewise homogeneous objects without sacrificing accuracy with respect to the conventional implementations.

GNSSR altimetry performance analysis for the GEROS experiment on board the international space station
http://hdl.handle.net/2117/106741
GNSSR altimetry performance analysis for the GEROS experiment on board the international space station
Camps Carmona, Adriano José; Hyuk, Park; Sekulic, Ivan; Rius Casals, Juan Manuel
The GEROSISS (GNSS rEflectometry, Radio Occultation and Scatterometry onboard International Space Station) is an innovative experiment for climate research, proposed in 2011 within a call of the European Space Agency (ESA). This proposal was the only one selected for further studies by ESA out of ~25 ones that were submitted. In this work, the instrument performance for the nearnadir altimetry (GNSSR) mode is assessed, including the effects of multipath in the ISS structure, the electromagneticbias, and the orbital height decay. In the absence of ionospheric scintillations, the altimetry rms error is <50 cm for a swath <~250 km and for U10 <10 m/s. If the transmitted power is 3 dB higher (likely to happen at beginning of life of the GNSS spacecrafts), mission requirements (rms error is <50 cm) are met for all ISS heights and for U10 up to 15 m/s. However, around 1.5 GHz, the ionosphere can induce significant fading, from 2 to >20 dB at equatorial regions, mainly after sunset, which will seriously degrade the altimetry and the scatterometry performances of the instrument.
20170724T10:54:59Z
Camps Carmona, Adriano José
Hyuk, Park
Sekulic, Ivan
Rius Casals, Juan Manuel
The GEROSISS (GNSS rEflectometry, Radio Occultation and Scatterometry onboard International Space Station) is an innovative experiment for climate research, proposed in 2011 within a call of the European Space Agency (ESA). This proposal was the only one selected for further studies by ESA out of ~25 ones that were submitted. In this work, the instrument performance for the nearnadir altimetry (GNSSR) mode is assessed, including the effects of multipath in the ISS structure, the electromagneticbias, and the orbital height decay. In the absence of ionospheric scintillations, the altimetry rms error is <50 cm for a swath <~250 km and for U10 <10 m/s. If the transmitted power is 3 dB higher (likely to happen at beginning of life of the GNSS spacecrafts), mission requirements (rms error is <50 cm) are met for all ISS heights and for U10 up to 15 m/s. However, around 1.5 GHz, the ionosphere can induce significant fading, from 2 to >20 dB at equatorial regions, mainly after sunset, which will seriously degrade the altimetry and the scatterometry performances of the instrument.

Error bound of the multilevel adaptive cross approximation (MLACA)
http://hdl.handle.net/2117/102827
Error bound of the multilevel adaptive cross approximation (MLACA)
Chen, Xinlei; Gu, Changqing; Heldring, Alexander; Li, Zhuo; Cao, Qunsheng
An error bound of the multilevel adaptive cross approximation (MLACA 1, which is a multilevel version of the adaptive cross approximationsingular value decomposition (ACASVD), is rigorously derived. For compressing an offdiagonal submatrix of the method of moments MAD impedance matrix with a binary tree, the Llevel MIACA includes L + 1 steps, and each step includes 2(L) ACASVD decompositions. If the relative Frobenius norm error of the ACASVD used in the MLACA is smaller than epsilon, the rigorous proof in this communication shows that the relative Frobenius norm error of the LIevel MLACA is smaller than (1 + epsilon)(L+1)  1. In practical applications, the error bound of the MLACA can be approximated as epsilon(L + 1), because epsilon is always << 1. The error upper bound can he used to control the accuracy of the MLACA. To ensure an error of the Llevel MLACA smaller than epsilon for different L, the ACASVD threshold can be set to (1 + epsilon)1/L+1  1, which approximately equals epsilon/(L + 1) for practical applications.
20170323T13:25:21Z
Chen, Xinlei
Gu, Changqing
Heldring, Alexander
Li, Zhuo
Cao, Qunsheng
An error bound of the multilevel adaptive cross approximation (MLACA 1, which is a multilevel version of the adaptive cross approximationsingular value decomposition (ACASVD), is rigorously derived. For compressing an offdiagonal submatrix of the method of moments MAD impedance matrix with a binary tree, the Llevel MIACA includes L + 1 steps, and each step includes 2(L) ACASVD decompositions. If the relative Frobenius norm error of the ACASVD used in the MLACA is smaller than epsilon, the rigorous proof in this communication shows that the relative Frobenius norm error of the LIevel MLACA is smaller than (1 + epsilon)(L+1)  1. In practical applications, the error bound of the MLACA can be approximated as epsilon(L + 1), because epsilon is always << 1. The error upper bound can he used to control the accuracy of the MLACA. To ensure an error of the Llevel MLACA smaller than epsilon for different L, the ACASVD threshold can be set to (1 + epsilon)1/L+1  1, which approximately equals epsilon/(L + 1) for practical applications.

From experimental campaigns to BEC  CP34 salinity products: Tribute to the Contributions of prof. Font to the SMOS Mission
http://hdl.handle.net/2117/102670
From experimental campaigns to BEC  CP34 salinity products: Tribute to the Contributions of prof. 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, Antonio; Portabella, Marcos; BallabreraPoy, Joaquim; GonzálezGambau, Verónica; Martínez, Justino; Villarino Villarino, Ramon; Enrique, Luis; Monerris Belda, Sandra; Bosch, Xavier; Sabia, Roberto; Talone, Marco; Piles Guillem, Maria; Pablos Hernánez, Miriam; Valencia, 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.
20170320T14:25:13Z
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, Antonio
Portabella, Marcos
BallabreraPoy, Joaquim
GonzálezGambau, Verónica
Martínez, Justino
Villarino Villarino, Ramon
Enrique, Luis
Monerris Belda, Sandra
Bosch, Xavier
Sabia, Roberto
Talone, Marco
Piles Guillem, Maria
Pablos Hernánez, Miriam
Valencia, 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.

Tangentialnormal surface testing for the nonconforming discretization of the electricfield integral equation
http://hdl.handle.net/2117/102423
Tangentialnormal surface testing for the nonconforming discretization of the electricfield integral equation
Úbeda Farré, Eduard; Sekulic, Ivan; Rius Casals, Juan Manuel; Heldring, Alexander
Nonconforming implementations of the electricfield integral equation (EFIE), based on the facetoriented monopolarRWG set, impose no continuity constraints in the expansion of the current between adjacent facets. These schemes become more versatile than the traditional edgeoriented schemes, based on the RWG set, because they simplify the management of junctions in composite objects and allow the analysis of nonconformal triangulations. Moreover, for closed moderately small conductors with edges and corners, they show improved accuracy with respect to the conventional RWGdiscretization. However, they lead to elaborate numerical schemes because the fields are tested inside the body, near the boundary surface, over volumetric subdomains attached to the surface meshing. In this letter, we present a new nonconforming discretization of the EFIE that results from
testing with RWG functions over pairs of triangles such that one triangle matches one facet of the surface triangulation and the other one is oriented perpendicularly, inside the body. This “tangentialnormal” testing scheme, based on surface integrals, simplifies considerably the matrix generation when compared to the volumetrically tested approaches.
©2016 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.
20170314T10:22:25Z
Úbeda Farré, Eduard
Sekulic, Ivan
Rius Casals, Juan Manuel
Heldring, Alexander
Nonconforming implementations of the electricfield integral equation (EFIE), based on the facetoriented monopolarRWG set, impose no continuity constraints in the expansion of the current between adjacent facets. These schemes become more versatile than the traditional edgeoriented schemes, based on the RWG set, because they simplify the management of junctions in composite objects and allow the analysis of nonconformal triangulations. Moreover, for closed moderately small conductors with edges and corners, they show improved accuracy with respect to the conventional RWGdiscretization. However, they lead to elaborate numerical schemes because the fields are tested inside the body, near the boundary surface, over volumetric subdomains attached to the surface meshing. In this letter, we present a new nonconforming discretization of the EFIE that results from
testing with RWG functions over pairs of triangles such that one triangle matches one facet of the surface triangulation and the other one is oriented perpendicularly, inside the body. This “tangentialnormal” testing scheme, based on surface integrals, simplifies considerably the matrix generation when compared to the volumetrically tested approaches.

High directivity fractal boundary microstrip patch antenna
http://hdl.handle.net/2117/98486
High directivity fractal boundary microstrip patch antenna
Borja Borau, Carmen; Font, G; Blanch Boris, Sebastián; Romeu Robert, Jordi
A novel patch antenna with a fractal boundary condition is proposed. Experimental and numerical results corroborate the fact that the fractal characteristic of the perimeter produces localised modes. This property is utilised in the design of a microstrip patch antenna with a measured directivity of 12.7 dB.
20161216T15:45:43Z
Borja Borau, Carmen
Font, G
Blanch Boris, Sebastián
Romeu Robert, Jordi
A novel patch antenna with a fractal boundary condition is proposed. Experimental and numerical results corroborate the fact that the fractal characteristic of the perimeter produces localised modes. This property is utilised in the design of a microstrip patch antenna with a measured directivity of 12.7 dB.

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.

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.

The Koch monopole: a small fractal antenna
http://hdl.handle.net/2117/98367
The Koch monopole: a small fractal antenna
Puente Baliarda, Carles; Romeu Robert, Jordi; Cardama Aznar, Ángel
Fractal objects have some unique geometrical properties. One of them is the possibility to enclose in a finite area an infinitely long curve. The resulting curve is highly convoluted being nowhere differentiable. One such curve is the Koch curve. In this paper, the behavior the Koch monopole is numerically and experimentally analyzed. The results show that as the number of iterations on the small fractal Koch monopole are increased, the Q of the antenna approaches the fundamental limit for small antennas.
20161215T15:34:42Z
Puente Baliarda, Carles
Romeu Robert, Jordi
Cardama Aznar, Ángel
Fractal objects have some unique geometrical properties. One of them is the possibility to enclose in a finite area an infinitely long curve. The resulting curve is highly convoluted being nowhere differentiable. One such curve is the Koch curve. In this paper, the behavior the Koch monopole is numerically and experimentally analyzed. The results show that as the number of iterations on the small fractal Koch monopole are increased, the Q of the antenna approaches the fundamental limit for small antennas.

Dual band fss with fractal elements
http://hdl.handle.net/2117/98359
Dual band fss with fractal elements
Romeu Robert, Jordi; RahmatSamii, Y
Experimental and computed results of a frequency selective surface (FSS) based on a certain type of fractal element are presented. The fractal element is a two iteration Sierpinski gasket dipole. Owing to the dual band behaviour of the two iteration Sierpinski gasket dipole, two stopbands are exhibited within the operating frequency band. This behaviour is obtained by arraying one simple element in a single layer frequency selective surface (FSS)
20161215T15:03:19Z
Romeu Robert, Jordi
RahmatSamii, Y
Experimental and computed results of a frequency selective surface (FSS) based on a certain type of fractal element are presented. The fractal element is a two iteration Sierpinski gasket dipole. Owing to the dual band behaviour of the two iteration Sierpinski gasket dipole, two stopbands are exhibited within the operating frequency band. This behaviour is obtained by arraying one simple element in a single layer frequency selective surface (FSS)