ANTENNALAB  Grup d'Antenes i Sistemes Radio
http://hdl.handle.net/2117/657
20180324T15:49:47Z

Hierarchical discretization of the PMCHWT formulation with jump current discontinuities for the scattering analysis of ferromagnetic objects
http://hdl.handle.net/2117/115097
Hierarchical discretization of the PMCHWT formulation with jump current discontinuities for the scattering analysis of ferromagnetic objects
Úbeda Farré, Eduard; Sekulic, Ivan; Rius Casals, Juan Manuel
In the discretization of the PoggioMillerChanHarringtonWuTsai (PMCHWT) formulation by the Method of Moments (MoM), the unknown currents are usually expanded with the divergenceconforming RWG set. Recently, the discretization of the PMCHWT formulation with the monopolarRWG basis functions, discontinuous across edges, has been successfully developed through a volumetrictetrahedral testing scheme. We present a novel evensurface oddvolumetric monopolarRWG PMCHWTdiscretization that relies on the rearrangement of the monopolarRWG set in terms of the RWG and the oddmonopolarRWG subsets. This scheme offers improved accuracy for a wider range of heights of the testing tetrahedral elements than the volumetrically tested monopolarRWG PMCHWTdiscretization in the analysis of small sharpedged ferromagnetic targets.
©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.
20180313T11:32:09Z
Úbeda Farré, Eduard
Sekulic, Ivan
Rius Casals, Juan Manuel
In the discretization of the PoggioMillerChanHarringtonWuTsai (PMCHWT) formulation by the Method of Moments (MoM), the unknown currents are usually expanded with the divergenceconforming RWG set. Recently, the discretization of the PMCHWT formulation with the monopolarRWG basis functions, discontinuous across edges, has been successfully developed through a volumetrictetrahedral testing scheme. We present a novel evensurface oddvolumetric monopolarRWG PMCHWTdiscretization that relies on the rearrangement of the monopolarRWG set in terms of the RWG and the oddmonopolarRWG subsets. This scheme offers improved accuracy for a wider range of heights of the testing tetrahedral elements than the volumetrically tested monopolarRWG PMCHWTdiscretization in the analysis of small sharpedged ferromagnetic targets.

Volumetric testing with wedges for a nonconforming discretization of the PMCHWT formulation
http://hdl.handle.net/2117/115091
Volumetric testing with wedges for a nonconforming discretization of the PMCHWT formulation
Sekulic, Ivan; Úbeda Farré, Eduard; Rius Casals, Juan Manuel
The monopolarRaoWiltonGlisson (RWG) discretization of the PoggioMillerChanHarringtonWuTsai (PMCHWT) integral equation imposes no continuity constraints in the current expansion across the edges arising from the discretization of the boundary surface. The numerical evaluation of the hypersingular kernel contributions can be carried out through the volumetric testing of the fields over a set of tetrahedral elements attached to the boundary surface of the target. This facetbased implementation becomes wellsuited for the scattering analysis of composite objects or nonconformal meshes. Furthermore, improved accuracy has been observed in the analysis of moderately small sharpedged dielectric objects and high contrasts with the proper choice of the height of the testing tetrahedral elements. In this paper, we introduce a novel monopolarRWG discretization of the PMCHWT formulation where wedge testing elements are adopted. We show with radar cross section results that this scheme offers improved accuracy for a wider range of heights of the testing elements than the approach with tetrahedral testing.
©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.
20180313T10:35:06Z
Sekulic, Ivan
Úbeda Farré, Eduard
Rius Casals, Juan Manuel
The monopolarRaoWiltonGlisson (RWG) discretization of the PoggioMillerChanHarringtonWuTsai (PMCHWT) integral equation imposes no continuity constraints in the current expansion across the edges arising from the discretization of the boundary surface. The numerical evaluation of the hypersingular kernel contributions can be carried out through the volumetric testing of the fields over a set of tetrahedral elements attached to the boundary surface of the target. This facetbased implementation becomes wellsuited for the scattering analysis of composite objects or nonconformal meshes. Furthermore, improved accuracy has been observed in the analysis of moderately small sharpedged dielectric objects and high contrasts with the proper choice of the height of the testing tetrahedral elements. In this paper, we introduce a novel monopolarRWG discretization of the PMCHWT formulation where wedge testing elements are adopted. We show with radar cross section results that this scheme offers improved accuracy for a wider range of heights of the testing elements than the approach with tetrahedral testing.

Improved accuracy in the scattering analysis of arbitrarily shaped ferromagnetic objects
http://hdl.handle.net/2117/115090
Improved accuracy in the scattering analysis of arbitrarily shaped ferromagnetic objects
Sekulic, Ivan; Úbeda Farré, Eduard; Rius Casals, Juan Manuel
The electromagnetic scattering analysis of arbitrarily shaped ferromagnetic bodies is usually carried out with the PoggioMillerChanHarringtonWuTsai (PMCHWT) integral equation. In the Method of Moments (MoM) discretization of the PMCHWT formulation, the RWG set is very
often adopted in the expansion of the unknown traces of the total electromagnetic fields over the boundary surface of the target. The RWGschemes are edgebased and become in general well
suited for the analysis of single targets meshed with conformal meshings, where adjacent triangles share common edges. However, their implementation for composite objects becomes
elaborate around junctions, where several regions intersect. In this paper, we expand the electric and magnetic field traces over the boundary surface with the monopolarRWG set, which
stands for a facetbased scheme. Unlike the divergenceconforming RWG set, which imposes normalcontinuity across edges, the monopolarRWG set is nonconforming because a fully
discontinuous transition across edges is established. This allows for the agile analysis of complex bodies or nonconformal meshes, with nonmatching edges between adjacent triangles. We show the improved RCSaccuracy for the monopolarRWG discretization of the PMCHWT, with respect to traditional RWGdiscretization, for an example of ferromagnetic object.
20180313T10:27:44Z
Sekulic, Ivan
Úbeda Farré, Eduard
Rius Casals, Juan Manuel
The electromagnetic scattering analysis of arbitrarily shaped ferromagnetic bodies is usually carried out with the PoggioMillerChanHarringtonWuTsai (PMCHWT) integral equation. In the Method of Moments (MoM) discretization of the PMCHWT formulation, the RWG set is very
often adopted in the expansion of the unknown traces of the total electromagnetic fields over the boundary surface of the target. The RWGschemes are edgebased and become in general well
suited for the analysis of single targets meshed with conformal meshings, where adjacent triangles share common edges. However, their implementation for composite objects becomes
elaborate around junctions, where several regions intersect. In this paper, we expand the electric and magnetic field traces over the boundary surface with the monopolarRWG set, which
stands for a facetbased scheme. Unlike the divergenceconforming RWG set, which imposes normalcontinuity across edges, the monopolarRWG set is nonconforming because a fully
discontinuous transition across edges is established. This allows for the agile analysis of complex bodies or nonconformal meshes, with nonmatching edges between adjacent triangles. We show the improved RCSaccuracy for the monopolarRWG discretization of the PMCHWT, with respect to traditional RWGdiscretization, for an example of ferromagnetic object.

Nonconforming discretization of the PMCHWT integral equation applied to arbitrarily shaped dielectric objects
http://hdl.handle.net/2117/115089
Nonconforming discretization of the PMCHWT integral equation applied to arbitrarily shaped dielectric objects
Sekulic, Ivan; Úbeda Farré, Eduard; Rius Casals, Juan Manuel
The PoggioMillerChanHarringtonWuTsai (PMCHWT) integral equation is widely used in the scattering analysis of dielectric bodies. The RWG set is normally adopted to expand the electric and magnetic currents in the Method of Moments (MoM) discretization of the PMCHWT formulation. This set preserves normal continuity across edges in the expansion of currents. However, in the analysis of composite objects, the imposition of such continuity constraint around junctions, where several regions intersect, becomes convoluted.
We present a new nonconforming discretization of the PMCHWT formulation so that currents are expanded with no continuity constraint across edges. This becomes wellsuited
for the analysis of composite objects or nonconformal meshes, where some adjacent facets have no common edges. We show RCS results where the nonconforming PMCHWT implementation, facetoriented, shows similar or better accuracy as the conventional approach, edgeoriented, for a given degree of meshing.
©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.
20180313T10:18:17Z
Sekulic, Ivan
Úbeda Farré, Eduard
Rius Casals, Juan Manuel
The PoggioMillerChanHarringtonWuTsai (PMCHWT) integral equation is widely used in the scattering analysis of dielectric bodies. The RWG set is normally adopted to expand the electric and magnetic currents in the Method of Moments (MoM) discretization of the PMCHWT formulation. This set preserves normal continuity across edges in the expansion of currents. However, in the analysis of composite objects, the imposition of such continuity constraint around junctions, where several regions intersect, becomes convoluted.
We present a new nonconforming discretization of the PMCHWT formulation so that currents are expanded with no continuity constraint across edges. This becomes wellsuited
for the analysis of composite objects or nonconformal meshes, where some adjacent facets have no common edges. We show RCS results where the nonconforming PMCHWT implementation, facetoriented, shows similar or better accuracy as the conventional approach, edgeoriented, for a given degree of meshing.

On the accuracy of the adaptive cross aproximation algorithm
http://hdl.handle.net/2117/114569
On the accuracy of the adaptive cross aproximation algorithm
Heldring, Alexander; Úbeda Farré, Eduard; Sekulic, Ivan; Rius Casals, Juan Manuel
This contribution identifies an often ignored source of uncertainty in the accuracy of the adaptive cross approximation algorithm, and proposes a combination of adaptations that reduce this uncertainty with negligible additional computational cost.
© 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.
20180227T16:45:52Z
Heldring, Alexander
Úbeda Farré, Eduard
Sekulic, Ivan
Rius Casals, Juan Manuel
This contribution identifies an often ignored source of uncertainty in the accuracy of the adaptive cross approximation algorithm, and proposes a combination of adaptations that reduce this uncertainty with negligible additional computational cost.

Frequency extrapolation of IEMEI linear system Coefficients in 2D
http://hdl.handle.net/2117/114558
Frequency extrapolation of IEMEI linear system Coefficients in 2D
Rius Casals, Juan Manuel; Heldring, Alexander; Úbeda Farré, Eduard
The Integral Equation MEI (IEMEI) method for the sparsification of Method of Moments linear system matrix is revisited here. It achieves cpu computation time and storage memory requirements of order O(N ) (for 2D perfectly conducting scatterers of arbitrary convex shape), which is –to our knowledge– the best asymptotic computational complexity ever achieved by integral equation methods. The aim of this paper is to present yet unpublished details of the algorithm to extrapolate the linear system coefficients and the latest results obtained using modern computers.
20180227T14:53:14Z
Rius Casals, Juan Manuel
Heldring, Alexander
Úbeda Farré, Eduard
The Integral Equation MEI (IEMEI) method for the sparsification of Method of Moments linear system matrix is revisited here. It achieves cpu computation time and storage memory requirements of order O(N ) (for 2D perfectly conducting scatterers of arbitrary convex shape), which is –to our knowledge– the best asymptotic computational complexity ever achieved by integral equation methods. The aim of this paper is to present yet unpublished details of the algorithm to extrapolate the linear system coefficients and the latest results obtained using modern computers.

A simple and effective microwave invisibility cloak based on frequency selective surfaces
http://hdl.handle.net/2117/114520
A simple and effective microwave invisibility cloak based on frequency selective surfaces
Yuste, Pedro; Rius Casals, Juan Manuel; Romeu Robert, Jordi; Blanch Boris, Sebastián; Heldring, Alexander; Úbeda Farré, Eduard
This paper presents the design, simulation, manufacturing and testing of a simple invisibility cloak based on a frequency selective surface (FSS). The work is focused on cloaking an electrically thin dielectric cylinder with an easy to manufacture FSS made of copper strips glued to the cylinder surface. In contrast to many papers in the literature, the full procedure from formulation to measurement results is presented
here. An original approach to obtain the effective surface
impedance of the cylindrical FSS from either simulated or
measured far fields is introduced. The measurement results show
excellent and relatively wide band performance of the cloak
prototype.
20180226T16:38:40Z
Yuste, Pedro
Rius Casals, Juan Manuel
Romeu Robert, Jordi
Blanch Boris, Sebastián
Heldring, Alexander
Úbeda Farré, Eduard
This paper presents the design, simulation, manufacturing and testing of a simple invisibility cloak based on a frequency selective surface (FSS). The work is focused on cloaking an electrically thin dielectric cylinder with an easy to manufacture FSS made of copper strips glued to the cylinder surface. In contrast to many papers in the literature, the full procedure from formulation to measurement results is presented
here. An original approach to obtain the effective surface
impedance of the cylindrical FSS from either simulated or
measured far fields is introduced. The measurement results show
excellent and relatively wide band performance of the cloak
prototype.

Assessment of LTCCbased dielectric flat lens antennas and switchedbeam arrays for future 5G millimeterwave communication systems
http://hdl.handle.net/2117/111960
Assessment of LTCCbased dielectric flat lens antennas and switchedbeam arrays for future 5G millimeterwave communication systems
Imbert Villà, Marc; Romeu Robert, Jordi; Baquero Escudero, M.; Martinez Ingles, Maria Teresa; MolinaGarcia Pardo, Jose Maria; Jofre Roca, Lluís
IEEE This paper presents design, LTCC fabrication, and full experimental verification of novel dielectric flat lens antennas for future high data rate 5G wireless communication systems in the 60 GHz band. We introduce and practically completely evaluate and compare the performance of three different inhomogeneous gradientindex dielectric lenses with the effective parameters circularly and cylindrically distributed. These lenses, despite their planar profile antenna configuration, allow full 2D beamscanning of high gain radiation beams. A timedomain spectroscopy system is used to practically evaluate the permittivity profile achieved with the LTCC manufacturing process, obtaining very good results to confirm the viability of fabricating inhomogeneous flat lenses in a mass production technology. Then, the lenses performance is evaluated in terms of radiation pattern parameters, maximum gain, beamscanning, bandwidth performance, efficiencies, and impedance matching in the whole frequency band of interest. Finally, the performance of the three lenses is also experimentally evaluated and compared to a single omnidirectional antenna and to a 10element uniform linear array (ULA) of omnidirectional antennas in real 60 GHz WPAN indoor lineofsight (LOS) and obstructedLOS environments, obtaining interesting and promising remarkable results in terms of measured received power and root mean square (RMS) delay spread. At the end of the paper, an innovative switchedbeam antenna array concept based on the presented cylindrically distributed effective parameters lens is also introduced and completely evaluated, confirming the potential applicability of the proposed antenna solution for future 5G wireless millimeterwave communication system.
© 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.
20171213T17:45:25Z
Imbert Villà, Marc
Romeu Robert, Jordi
Baquero Escudero, M.
Martinez Ingles, Maria Teresa
MolinaGarcia Pardo, Jose Maria
Jofre Roca, Lluís
IEEE This paper presents design, LTCC fabrication, and full experimental verification of novel dielectric flat lens antennas for future high data rate 5G wireless communication systems in the 60 GHz band. We introduce and practically completely evaluate and compare the performance of three different inhomogeneous gradientindex dielectric lenses with the effective parameters circularly and cylindrically distributed. These lenses, despite their planar profile antenna configuration, allow full 2D beamscanning of high gain radiation beams. A timedomain spectroscopy system is used to practically evaluate the permittivity profile achieved with the LTCC manufacturing process, obtaining very good results to confirm the viability of fabricating inhomogeneous flat lenses in a mass production technology. Then, the lenses performance is evaluated in terms of radiation pattern parameters, maximum gain, beamscanning, bandwidth performance, efficiencies, and impedance matching in the whole frequency band of interest. Finally, the performance of the three lenses is also experimentally evaluated and compared to a single omnidirectional antenna and to a 10element uniform linear array (ULA) of omnidirectional antennas in real 60 GHz WPAN indoor lineofsight (LOS) and obstructedLOS environments, obtaining interesting and promising remarkable results in terms of measured received power and root mean square (RMS) delay spread. At the end of the paper, an innovative switchedbeam antenna array concept based on the presented cylindrically distributed effective parameters lens is also introduced and completely evaluated, confirming the potential applicability of the proposed antenna solution for future 5G wireless millimeterwave communication system.

Annual traffic noise levels estimation based on temporal stratification
http://hdl.handle.net/2117/111392
Annual traffic noise levels estimation based on temporal stratification
Quintero, G.; Balastegui Manso, Andreu; Romeu Garbí, Jordi
This paper proposes a temporal sampling strategy that increases the accuracy of longterm noise level estimation and allows to establish the estimation error according to the number of sampled days. Days of the week are stratified into working days and weekend days. This research shows how to use measurements of Leq on working days to estimate the corresponding values for weekend days. This is possible because working days have higher noise levels and less variability than weekend days. The improvement in accuracy allows for a reduction in the number of required sampled days compared to taking samples randomly, which would help to reduce the uncertainty in environmental noise assessment. As a reference, to obtain a 90% confidence interval of ±1 dB for Lday, the proposed sampling strategy reduces the required measurement days by more than 38%. For LDEN, the reduction is close to 18% of the total number of days. The proposed strategy could be adapted to different environments by simply changing a few parameters.
© 2017. This version is made available under the CCBYNCND 4.0 license http://creativecommons.org/licenses/byncnd/4.0/
20171130T15:50:29Z
Quintero, G.
Balastegui Manso, Andreu
Romeu Garbí, Jordi
This paper proposes a temporal sampling strategy that increases the accuracy of longterm noise level estimation and allows to establish the estimation error according to the number of sampled days. Days of the week are stratified into working days and weekend days. This research shows how to use measurements of Leq on working days to estimate the corresponding values for weekend days. This is possible because working days have higher noise levels and less variability than weekend days. The improvement in accuracy allows for a reduction in the number of required sampled days compared to taking samples randomly, which would help to reduce the uncertainty in environmental noise assessment. As a reference, to obtain a 90% confidence interval of ±1 dB for Lday, the proposed sampling strategy reduces the required measurement days by more than 38%. For LDEN, the reduction is close to 18% of the total number of days. The proposed strategy could be adapted to different environments by simply changing a few parameters.

Aplicación del método de la descomposición modal al análisis de radomos esféricos
http://hdl.handle.net/2117/108850
Aplicación del método de la descomposición modal al análisis de radomos esféricos
Romeu Robert, Jordi
20171019T10:32:16Z
Romeu Robert, Jordi