Ponències/Comunicacions de congressos
http://hdl.handle.net/2117/659
2017-03-14T06:33:00ZOn the accuracy of the Adaptive Cross Approximation algorithm
http://hdl.handle.net/2117/102208
On the accuracy of the Adaptive Cross Approximation algorithm
Heldring, Alexander; Úbeda Farré, Eduard; Rius Casals, Juan Manuel
This contribution identifies an often ignored source of uncertainty in the accuracy of the Adaptive Cross Approximation (ACA) algorithm.
2017-03-09T13:43:25ZHeldring, AlexanderÚbeda Farré, EduardRius Casals, Juan ManuelThis contribution identifies an often ignored source of uncertainty in the accuracy of the Adaptive Cross Approximation (ACA) algorithm.Balanced tangential testing for the nonconforming discretization of the Electric-Field Integral Equation on open PeC surfaces
http://hdl.handle.net/2117/99435
Balanced tangential testing for the nonconforming discretization of the Electric-Field Integral Equation on open PeC surfaces
Úbeda Farré, Eduard; Sekulic, Ivan; Rius Casals, Juan Manuel
Recent attention has been devoted to the development of nonconforming implementations of the Electric-Field Integral Equation (EFIE), which impose no continuity constraints in the expansion of the current between adjacent
facets. These schemes, based on the facet-oriented monopolar-RWG set, become more versatile than the traditional edge-oriented schemes, based on the RWG set, because they simplify the discretization around junctions in composite
objects and because they can handle nonconformal triangulations. The existing nonconforming implementations tackle the numerical evaluation of the inherent hypersingular Kernel contributions of the EFIE by testing the fields over
volumetric or surface domains attached to the boundary surface inside the conductor. Hence, the application of such schemes is restricted to closed PeC surfaces. In this paper, we present a novel nonconforming implementation of the
EFIE that allows the scattering analysis of open PeC surfaces by testing the fields with a new, 'balancedtangential', strategy. We show for several examples of open PeC surfaces, infinitely long (2D) or arbitrarily shaped (3D), that the proposed scheme provides similar or slightly better accuracy than the RWG-discretization of the EFIE and same meshing.
2017-01-17T11:31:35ZÚbeda Farré, EduardSekulic, IvanRius Casals, Juan ManuelRecent attention has been devoted to the development of nonconforming implementations of the Electric-Field Integral Equation (EFIE), which impose no continuity constraints in the expansion of the current between adjacent
facets. These schemes, based on the facet-oriented monopolar-RWG set, become more versatile than the traditional edge-oriented schemes, based on the RWG set, because they simplify the discretization around junctions in composite
objects and because they can handle nonconformal triangulations. The existing nonconforming implementations tackle the numerical evaluation of the inherent hypersingular Kernel contributions of the EFIE by testing the fields over
volumetric or surface domains attached to the boundary surface inside the conductor. Hence, the application of such schemes is restricted to closed PeC surfaces. In this paper, we present a novel nonconforming implementation of the
EFIE that allows the scattering analysis of open PeC surfaces by testing the fields with a new, 'balancedtangential', strategy. We show for several examples of open PeC surfaces, infinitely long (2D) or arbitrarily shaped (3D), that the proposed scheme provides similar or slightly better accuracy than the RWG-discretization of the EFIE and same meshing.Dielectric flat lenses with cylindrically distributed parameters for millimeter-wave applications
http://hdl.handle.net/2117/98172
Dielectric flat lenses with cylindrically distributed parameters for millimeter-wave applications
Imbert, M.; Romeu Robert, Jordi; Jofre Roca, Lluís
The design and performance evaluation of an inhomogeneous dielectric flat lens with the effective relative permittivity cylindrically distributed is presented. In order to achieve high-data rate wireless communications for future broadband networks at millimeter-wave frequencies it is essential to dispose of high directive antennas with beamsteering capabilities. In consequence, in this paper we introduce a novel design of an inhomogeneous dielectric flat lens with an effective gradient-index in one axis, while a constant-index is maintained along the other one. With this cylindrical effective parameter distribution, the beam-scanning can be performed in one plane by moving (or selecting) the position of a radiating single element along the gradient-index axis, whereas the beam can be maintained invariant in the other direction, in which the effective parameters are kept constant, despite changing the radiating element
position in this particular axis. In this way, the beamscanning can be achieved in the constant-index axis of the lens by means of a different technique (e.g. frequency-scanned array), in order to reduce the switch elements needed, to finally perform the scan in both theta and phi directions of the space.
2016-12-13T15:33:11ZImbert, M.Romeu Robert, JordiJofre Roca, LluísThe design and performance evaluation of an inhomogeneous dielectric flat lens with the effective relative permittivity cylindrically distributed is presented. In order to achieve high-data rate wireless communications for future broadband networks at millimeter-wave frequencies it is essential to dispose of high directive antennas with beamsteering capabilities. In consequence, in this paper we introduce a novel design of an inhomogeneous dielectric flat lens with an effective gradient-index in one axis, while a constant-index is maintained along the other one. With this cylindrical effective parameter distribution, the beam-scanning can be performed in one plane by moving (or selecting) the position of a radiating single element along the gradient-index axis, whereas the beam can be maintained invariant in the other direction, in which the effective parameters are kept constant, despite changing the radiating element
position in this particular axis. In this way, the beamscanning can be achieved in the constant-index axis of the lens by means of a different technique (e.g. frequency-scanned array), in order to reduce the switch elements needed, to finally perform the scan in both theta and phi directions of the space.Edge diffraction computation using GRECO
http://hdl.handle.net/2117/98166
Edge diffraction computation using GRECO
Rius Casals, Juan Manuel; Carbo, Alex; Úbeda Farré, Eduard; Heldring, Alexander
This paper addresses two graphical processing approaches for computation of edge scattering with Physical Theory of Diffraction (PTD) high-frequency approximation. One is based on processing only a bitmap containing an image of the radar target, while the other uses a bitmap graphical processing algorithm to identify illuminated and shadowed facet mesh vertices, published in 2014, and then computes PTD diffraction coefficients for illuminated edges in the conventional way. The first approach is much faster for models containing a very large number of facets, but introduces pixel discretization noise, that can be alleviated by using larger bitmaps.
2016-12-13T15:15:43ZRius Casals, Juan ManuelCarbo, AlexÚbeda Farré, EduardHeldring, AlexanderThis paper addresses two graphical processing approaches for computation of edge scattering with Physical Theory of Diffraction (PTD) high-frequency approximation. One is based on processing only a bitmap containing an image of the radar target, while the other uses a bitmap graphical processing algorithm to identify illuminated and shadowed facet mesh vertices, published in 2014, and then computes PTD diffraction coefficients for illuminated edges in the conventional way. The first approach is much faster for models containing a very large number of facets, but introduces pixel discretization noise, that can be alleviated by using larger bitmaps.Constraints in azimuth resolution by refocusing slowly moving targets from single-look complex SAR vignettes
http://hdl.handle.net/2117/96571
Constraints in azimuth resolution by refocusing slowly moving targets from single-look complex SAR vignettes
Yam Ontiveros, Luis Eduardo; Mallorquí Franquet, Jordi Joan; Rius Casals, Juan Manuel
Accessing the raw data of spaceborne SAR systems is not always possible to refocus blurred SAR signatures of vessels. Instead, the single-look complex (SLC) data is usually more available, but since the vessel motion can shift the Doppler centroid frequency there can be a partial suppression of the target's spectrum during the windowing in the image formation, limiting the achievable azimuth resolution of the SAR signature. Simulations of slowly moving point-targets and complex vessels with spaceborne SAR sensors (C- and X-band) are carried out to examine the impact of the target motion on the azimuth resolution of its SAR signature.
2016-11-11T15:36:31ZYam Ontiveros, Luis EduardoMallorquí Franquet, Jordi JoanRius Casals, Juan ManuelAccessing the raw data of spaceborne SAR systems is not always possible to refocus blurred SAR signatures of vessels. Instead, the single-look complex (SLC) data is usually more available, but since the vessel motion can shift the Doppler centroid frequency there can be a partial suppression of the target's spectrum during the windowing in the image formation, limiting the achievable azimuth resolution of the SAR signature. Simulations of slowly moving point-targets and complex vessels with spaceborne SAR sensors (C- and X-band) are carried out to examine the impact of the target motion on the azimuth resolution of its SAR signature.Pixel reconfigurable antennas: towards low-complexity full reconfiguration
http://hdl.handle.net/2117/93034
Pixel reconfigurable antennas: towards low-complexity full reconfiguration
Rodrigo López, Daniel; Romeu Robert, Jordi; Cetiner, Bedri Artug; Jofre Roca, Lluís
The explosive growth of wireless communications has brought new requirements in terms of compactness, mobility and multi-functionality that make reconfigurable antennas excellent candidates for future wireless networks. Pixel antennas are particularly interesting due to their ability to dynamically reshape its active surface to change
their properties. Despite their outstanding reconfigurability, pixel antennas require a level of complexity and cost that prevents their implementation in commercial systems. In this paper we cover the main concepts for the design and optimization of pixel antennas and propose novel pixel architectures. These new pixel structures allow us to reduce the antenna complexity, maximize their reconfigurability and eventually contribute to the development of pixel antennas
from a conceptual structure to a practical reconfigurable architecture.
2016-11-07T14:16:26ZRodrigo López, DanielRomeu Robert, JordiCetiner, Bedri ArtugJofre Roca, LluísThe explosive growth of wireless communications has brought new requirements in terms of compactness, mobility and multi-functionality that make reconfigurable antennas excellent candidates for future wireless networks. Pixel antennas are particularly interesting due to their ability to dynamically reshape its active surface to change
their properties. Despite their outstanding reconfigurability, pixel antennas require a level of complexity and cost that prevents their implementation in commercial systems. In this paper we cover the main concepts for the design and optimization of pixel antennas and propose novel pixel architectures. These new pixel structures allow us to reduce the antenna complexity, maximize their reconfigurability and eventually contribute to the development of pixel antennas
from a conceptual structure to a practical reconfigurable architecture.Análisis de antenas de reflector mediante procesado gráfico
http://hdl.handle.net/2117/88574
Análisis de antenas de reflector mediante procesado gráfico
Vall-Llossera Ferran, Mercedes Magdalena; Salazar, C; Rius Casals, Juan Manuel; Cardama Aznar, Ángel
The aim of this article is to show a new technique for calculating the Radiation Pattern of arbitrary geometry reflector antennas. We use the Graphical processing technique developed in this group for Radar Cross Section Analysing [1] to obtain the whole geometry information of the reflector antenna necessary to obtain his radiation pattern. This program can obtain the first contribution using Phisical Optics technique, but also can obtain second order contribution.
2016-07-06T15:15:30ZVall-Llossera Ferran, Mercedes MagdalenaSalazar, CRius Casals, Juan ManuelCardama Aznar, ÁngelThe aim of this article is to show a new technique for calculating the Radiation Pattern of arbitrary geometry reflector antennas. We use the Graphical processing technique developed in this group for Radar Cross Section Analysing [1] to obtain the whole geometry information of the reflector antenna necessary to obtain his radiation pattern. This program can obtain the first contribution using Phisical Optics technique, but also can obtain second order contribution.Cálculo de radiación en 3 dimensiones mediante el método de los elementos de contorno
http://hdl.handle.net/2117/88569
Cálculo de radiación en 3 dimensiones mediante el método de los elementos de contorno
Duffo Ubeda, Núria; Rius Casals, Juan Manuel; Cardama Aznar, Ángel
In order to analize the electromagnetic fields generated by perfectly conducting bodies whichever it is its geometry, the Boundary Element Method is applied.
The basic formulation and associated items (integral equations to solve, surface and thin wire discretization, fields interpolation and numerical integration) are comented.
Results of problems of radiation are given and compared with available analytic solutions, which demostrate the good accurancy of the method.
2016-07-06T14:28:17ZDuffo Ubeda, NúriaRius Casals, Juan ManuelCardama Aznar, ÁngelIn order to analize the electromagnetic fields generated by perfectly conducting bodies whichever it is its geometry, the Boundary Element Method is applied.
The basic formulation and associated items (integral equations to solve, surface and thin wire discretization, fields interpolation and numerical integration) are comented.
Results of problems of radiation are given and compared with available analytic solutions, which demostrate the good accurancy of the method.Algoritmo iterativo de propagación espectral para el cálculo de RCS en cavidades conductoras
http://hdl.handle.net/2117/88568
Algoritmo iterativo de propagación espectral para el cálculo de RCS en cavidades conductoras
Rius Casals, Juan Manuel; Cardama Aznar, Ángel; Jofre Roca, Lluís
One of the most difficult problems in the RCS prediction of a complex target is the analysis of the cavities existing at the air inlets and outlets of engines. The geometrical complexity of these structures makes difficult the analysis by modal, ray or beam techniques, while their huge electrical size makes computationally prohibitive the analysis by matrix methods. For these reasons, we have developed an iterative spectral propagation algorithm which can be used to calculate the RCS of electrically intermediate or large cavities with certain geometrical features.
2016-07-06T14:15:41ZRius Casals, Juan ManuelCardama Aznar, ÁngelJofre Roca, LluísOne of the most difficult problems in the RCS prediction of a complex target is the analysis of the cavities existing at the air inlets and outlets of engines. The geometrical complexity of these structures makes difficult the analysis by modal, ray or beam techniques, while their huge electrical size makes computationally prohibitive the analysis by matrix methods. For these reasons, we have developed an iterative spectral propagation algorithm which can be used to calculate the RCS of electrically intermediate or large cavities with certain geometrical features.Caracterización electromagnética de materiales RAM mediante medidas en espacio libre
http://hdl.handle.net/2117/88567
Caracterización electromagnética de materiales RAM mediante medidas en espacio libre
Blanch Boris, Sebastián; Cardama Aznar, Ángel; Jofre Roca, Lluís
A free-space measurement system in the 2-JBGHz frequency range is used to measure the reflection and transmission coefficients of planar samples. The complex electric permittivity and the magnetic permeability are calculated from the measured values of S11 and S21. The measurement system consists of broadband transmit and receive antennas, a network analyzer, mode transitions, and a computer. Error due to multiple reflections between antennas via the swjace of the sample are corrected by using a free space T.R.L. calibration technique.
2016-07-06T14:06:32ZBlanch Boris, SebastiánCardama Aznar, ÁngelJofre Roca, LluísA free-space measurement system in the 2-JBGHz frequency range is used to measure the reflection and transmission coefficients of planar samples. The complex electric permittivity and the magnetic permeability are calculated from the measured values of S11 and S21. The measurement system consists of broadband transmit and receive antennas, a network analyzer, mode transitions, and a computer. Error due to multiple reflections between antennas via the swjace of the sample are corrected by using a free space T.R.L. calibration technique.