ANTENNALAB  Grup d'Antenes i Sistemes Radio
http://hdl.handle.net/2117/657
20160210T22:24:17Z

Design and performance evaluation of a dielectric flat lens antenna for millimeterwave applications
http://hdl.handle.net/2117/81616
Design and performance evaluation of a dielectric flat lens antenna for millimeterwave applications
Imbert Villà, Marc; Papió, Anna; de Flaviis, Franco; Jofre Roca, Lluís; Romeu Robert, Jordi
In this letter, a practical fabrication of a novel inhomogeneous gradientindex dielectric flat lens for millimeterwave applications is presented. A previous theoretical design of a dielectric flat lens composed of different permittivity materials is now modeled and analyzed for a practical prototype fabrication and performance evaluation at 60 and 77 GHz. The measurement results at 60 GHz show that with the novel gradientindex dielectric flat lens antenna prototype, we can achieve up to 18.3 dB of broadside gain, beamsteering capabilities in both planes from 30 degrees to +30 degrees with around 15 dB of gain, and up to +/ 45 degrees with around 14 dB of gain, with low sidelobe levels. At 77 GHz, the performance evaluation shows that we can obtain up to 18.9 dB of broadside gain, beamsteering capabilities in both planes from 30 degrees to +30 degrees with around 17 dB of gain and low sidelobe levels, and up to +/ 45 degrees with around 15 dB of gain. This novel design leads to a lowcost, lowprofile, and lightweight antenna solution, easy to integrate in a compact millimeterwave wireless communication system.
©2014 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.
20160118T14:51:39Z
Imbert Villà, Marc
Papió, Anna
de Flaviis, Franco
Jofre Roca, Lluís
Romeu Robert, Jordi
In this letter, a practical fabrication of a novel inhomogeneous gradientindex dielectric flat lens for millimeterwave applications is presented. A previous theoretical design of a dielectric flat lens composed of different permittivity materials is now modeled and analyzed for a practical prototype fabrication and performance evaluation at 60 and 77 GHz. The measurement results at 60 GHz show that with the novel gradientindex dielectric flat lens antenna prototype, we can achieve up to 18.3 dB of broadside gain, beamsteering capabilities in both planes from 30 degrees to +30 degrees with around 15 dB of gain, and up to +/ 45 degrees with around 14 dB of gain, with low sidelobe levels. At 77 GHz, the performance evaluation shows that we can obtain up to 18.9 dB of broadside gain, beamsteering capabilities in both planes from 30 degrees to +30 degrees with around 17 dB of gain and low sidelobe levels, and up to +/ 45 degrees with around 15 dB of gain. This novel design leads to a lowcost, lowprofile, and lightweight antenna solution, easy to integrate in a compact millimeterwave wireless communication system.

Selfbiased reconfigurable graphene stacks for terahertz plasmonics
http://hdl.handle.net/2117/81043
Selfbiased reconfigurable graphene stacks for terahertz plasmonics
Gomez Diaz, J. S.; Moldovan, C; Capdevila Cascante, Santiago; Romeu Robert, Jordi; Bernard, L. S.; Magrez, A; Ionescu, A. M.; Perruisseau Carrier, Julien
The gatecontrollable complex conductivity of graphene offers unprecedented opportunities for reconfigurable plasmonics at terahertz and midinfrared frequencies. However, the requirement of a gating electrode close to graphene and the single 'control knob' that this approach offers limits the practical implementation and performance of these devices. Here we report on graphene stacks composed of two or more graphene monolayers separated by electrically thin dielectrics and present a simple and rigorous theoretical framework for their characterization. In a first implementation, two graphene layers gate each other, thereby behaving as a controllable single equivalent layer but without any additional gating structure. Second, we show that adding an additional gate allows independent control of the complex conductivity of each layer within the stack and provides enhanced control on the stack equivalent complex conductivity. These results are very promising for the development of THz and midinfrared plasmonic devices with enhanced performance and reconfiguration capabilities.
20151223T14:01:12Z
Gomez Diaz, J. S.
Moldovan, C
Capdevila Cascante, Santiago
Romeu Robert, Jordi
Bernard, L. S.
Magrez, A
Ionescu, A. M.
Perruisseau Carrier, Julien
The gatecontrollable complex conductivity of graphene offers unprecedented opportunities for reconfigurable plasmonics at terahertz and midinfrared frequencies. However, the requirement of a gating electrode close to graphene and the single 'control knob' that this approach offers limits the practical implementation and performance of these devices. Here we report on graphene stacks composed of two or more graphene monolayers separated by electrically thin dielectrics and present a simple and rigorous theoretical framework for their characterization. In a first implementation, two graphene layers gate each other, thereby behaving as a controllable single equivalent layer but without any additional gating structure. Second, we show that adding an additional gate allows independent control of the complex conductivity of each layer within the stack and provides enhanced control on the stack equivalent complex conductivity. These results are very promising for the development of THz and midinfrared plasmonic devices with enhanced performance and reconfiguration capabilities.

Volumetric testing parallel to the boundary surface for a nonconforming discretization of the electricfield integral equation
http://hdl.handle.net/2117/79425
Volumetric testing parallel to the boundary surface for a nonconforming discretization of the electricfield integral equation
Úbeda Farré, Eduard; Rius Casals, Juan Manuel; Heldring, Alexander; Sekulic, Ivan
The volumetric monopolarRWG discretization of the electricfield integral equation (EFIE) imposes no continuity constraint across edges in the surface discretization around a closed conductor. The current is expanded with the monopolarRWG set and the electric field is tested over a set of tetrahedral elements attached to the boundary surface. This scheme is facetoriented and therefore, well suited for the scattering analysis of nonconformal meshes or composite objects. The observed accuracy, though, is only competitive with respect to the RWGdiscretization for a restricted range of heights of the tetrahedral elements. In this communication, we introduce a novel implementation of the volumetric monopolarRWG discretization of the EFIE with testing over a set of wedges. We show with RCS and nearfield results that this scheme offers improved accuracy for a wider range of heights than the approach with tetrahedral testing. The application of the wedge testing to the evensurface oddvolumetric monopolarRWG discretization of the EFIE, edgeoriented and therefore less versatile, shows similar accuracy as with tetrahedral testing, which is a sign of robustness.
© 2015 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.
20151118T14:40:14Z
Úbeda Farré, Eduard
Rius Casals, Juan Manuel
Heldring, Alexander
Sekulic, Ivan
The volumetric monopolarRWG discretization of the electricfield integral equation (EFIE) imposes no continuity constraint across edges in the surface discretization around a closed conductor. The current is expanded with the monopolarRWG set and the electric field is tested over a set of tetrahedral elements attached to the boundary surface. This scheme is facetoriented and therefore, well suited for the scattering analysis of nonconformal meshes or composite objects. The observed accuracy, though, is only competitive with respect to the RWGdiscretization for a restricted range of heights of the tetrahedral elements. In this communication, we introduce a novel implementation of the volumetric monopolarRWG discretization of the EFIE with testing over a set of wedges. We show with RCS and nearfield results that this scheme offers improved accuracy for a wider range of heights than the approach with tetrahedral testing. The application of the wedge testing to the evensurface oddvolumetric monopolarRWG discretization of the EFIE, edgeoriented and therefore less versatile, shows similar accuracy as with tetrahedral testing, which is a sign of robustness.

Towards microwave system for realtime medical imaging
http://hdl.handle.net/2117/78382
Towards microwave system for realtime medical imaging
Guardiola Garcia, Marta; Buitrago Ventura, Santiago; Romeu Robert, Jordi; Jofre Roca, Lluís
Microwave tomography is proposed for medical diagnosis using Magnitude Combined tomographic algorithm. A proofofconcept experimental system was build and an inhomogeneous breast phantom with a tumor embedded was successfully reconstructed in less than 30 seconds per frequency. The motivation for this study is the future development of an imaging prototype for head imaging.
20151027T16:51:37Z
Guardiola Garcia, Marta
Buitrago Ventura, Santiago
Romeu Robert, Jordi
Jofre Roca, Lluís
Microwave tomography is proposed for medical diagnosis using Magnitude Combined tomographic algorithm. A proofofconcept experimental system was build and an inhomogeneous breast phantom with a tumor embedded was successfully reconstructed in less than 30 seconds per frequency. The motivation for this study is the future development of an imaging prototype for head imaging.

Integral Equation MEI (IEMEI) analysis of homogeneus dielectric and plasmonic media in 2D
http://hdl.handle.net/2117/77176
Integral Equation MEI (IEMEI) analysis of homogeneus dielectric and plasmonic media in 2D
Rius Casals, Juan Manuel; Planes Conangla, Gerard; Úbeda Farré, Eduard; Heldring, Alexander
This paper revisits the IEMEI method and proposes a new formulation for highloss didectric piecewisehomogeneous media. The aim of this work is lo assess if the bigh localization of surface plasmon polarltons helps in acbieving bigher matrix sparsification and therefore reduces the approximation error and the computational cost of the linear system solution, compared with the not very successful performance of IEMEI for perfectly conducting scatterers.
20150929T14:59:39Z
Rius Casals, Juan Manuel
Planes Conangla, Gerard
Úbeda Farré, Eduard
Heldring, Alexander
This paper revisits the IEMEI method and proposes a new formulation for highloss didectric piecewisehomogeneous media. The aim of this work is lo assess if the bigh localization of surface plasmon polarltons helps in acbieving bigher matrix sparsification and therefore reduces the approximation error and the computational cost of the linear system solution, compared with the not very successful performance of IEMEI for perfectly conducting scatterers.

Adapted ACA algorithm with improved efficiency and compression rate
http://hdl.handle.net/2117/77175
Adapted ACA algorithm with improved efficiency and compression rate
Heldring, Alexander; Úbeda Farré, Eduard; Rius Casals, Juan Manuel
This contribution proposes an adapted version of the popular Adaptive Cross Approximation algorithm for block wise compression of Method of Moments impedance matrices.
The estimation of the matrix block Frobenius norm, necessary to
know the relative error in the compressed representation takes
up a substantial percentage of the total computation time. In the
adapted version it is replaced by a stochastic process with
negligible cost. The involved uncertainly is eliminated using an a
posteriori SVD recompression which, as a fortunate sideeffect,
yields an important additional reduction of the compressed rank
20150929T14:52:25Z
Heldring, Alexander
Úbeda Farré, Eduard
Rius Casals, Juan Manuel
This contribution proposes an adapted version of the popular Adaptive Cross Approximation algorithm for block wise compression of Method of Moments impedance matrices.
The estimation of the matrix block Frobenius norm, necessary to
know the relative error in the compressed representation takes
up a substantial percentage of the total computation time. In the
adapted version it is replaced by a stochastic process with
negligible cost. The involved uncertainly is eliminated using an a
posteriori SVD recompression which, as a fortunate sideeffect,
yields an important additional reduction of the compressed rank

Design and implementation of multispectral remote sensing capabilities in the U.P.C. lidar system
http://hdl.handle.net/2117/27937
Design and implementation of multispectral remote sensing capabilities in the U.P.C. lidar system
Kumar, Dhiraj; Rocadenbosch Burillo, Francisco
20150515T12:03:01Z
Kumar, Dhiraj
Rocadenbosch Burillo, Francisco

Stochastic estimation of the Frobenius norm in the ACA convergence criterion
http://hdl.handle.net/2117/27519
Stochastic estimation of the Frobenius norm in the ACA convergence criterion
Heldring, Alexander; Úbeda Farré, Eduard; Rius Casals, Juan Manuel
The adaptive cross approximation (ACA) algorithm has been used in many fast Integral Equation solvers for electromagnetic Radiation and Scattering problems. It efficiently computes a low rank approximation to the interaction matrix between mutually distant parts of a scattering object. The ACA is an iterative algorithm that needs an accurate and efficient convergence criterion. The evaluation of this criterion may consume a considerable part of the computational resources. This communication presents an efficient new way to evaluate the convergence criterion, using a stochastic approach.
20150422T13:58:34Z
Heldring, Alexander
Úbeda Farré, Eduard
Rius Casals, Juan Manuel
The adaptive cross approximation (ACA) algorithm has been used in many fast Integral Equation solvers for electromagnetic Radiation and Scattering problems. It efficiently computes a low rank approximation to the interaction matrix between mutually distant parts of a scattering object. The ACA is an iterative algorithm that needs an accurate and efficient convergence criterion. The evaluation of this criterion may consume a considerable part of the computational resources. This communication presents an efficient new way to evaluate the convergence criterion, using a stochastic approach.

Cronología de las TIC
http://hdl.handle.net/2117/27266
Cronología de las TIC
Elias Fusté, Antonio
És un recorregut cronològic i conceptual sobre els científics, inventors i tecnòlegs que han provocat l’actual situació socioeconòmica que coneixem com Societat de la Informació
20150413T09:20:40Z
Elias Fusté, Antonio

Frequency, radiation pattern and polarization reconfigurable antenna using a parasitic pixel layer
http://hdl.handle.net/2117/27121
Frequency, radiation pattern and polarization reconfigurable antenna using a parasitic pixel layer
Rodrigo López, Daniel; Cetiner, Bedri Artug
This communication presents a reconfigurable antenna capable of independently reconfiguring the operating frequency, radiation pattern and polarization. A switched grid of small metallic patches, known as pixel surface, is used as a parasitic layer to provide reconfiguration capabilities to existing antennas acting as driven element. The parasitic pixel layer presents advantages such as low profile, integrability and costeffective fabrication. A fully operational prototype has been designed, fabricated and its compound reconfiguration capabilities have been characterized. The prototype combines a patch antenna and a parasitic pixel surface consisting of 6 x 6 pixels, with an overall size of 0.6 lambda x 0.6 lambda and 60 PINdiode switches. The antenna simultaneously tunes its operation frequency over a 25% frequency range, steers the radiation beam over +/ 30 degrees in E and Hplanes, and switches between four different polarizations ((x) over cap, (y) over cap, LHCP, RHCP). The average antenna gain among the different parameter combinations is 4 dB, reaching 67 dB for the most advantageous combinations. The distance between the driven and the parasitic layers determines the tradeoff between frequency tuning range (12% to 25%) and radiation efficiency (45% to 55%).
20150331T21:59:14Z
Rodrigo López, Daniel
Cetiner, Bedri Artug
This communication presents a reconfigurable antenna capable of independently reconfiguring the operating frequency, radiation pattern and polarization. A switched grid of small metallic patches, known as pixel surface, is used as a parasitic layer to provide reconfiguration capabilities to existing antennas acting as driven element. The parasitic pixel layer presents advantages such as low profile, integrability and costeffective fabrication. A fully operational prototype has been designed, fabricated and its compound reconfiguration capabilities have been characterized. The prototype combines a patch antenna and a parasitic pixel surface consisting of 6 x 6 pixels, with an overall size of 0.6 lambda x 0.6 lambda and 60 PINdiode switches. The antenna simultaneously tunes its operation frequency over a 25% frequency range, steers the radiation beam over +/ 30 degrees in E and Hplanes, and switches between four different polarizations ((x) over cap, (y) over cap, LHCP, RHCP). The average antenna gain among the different parameter combinations is 4 dB, reaching 67 dB for the most advantageous combinations. The distance between the driven and the parasitic layers determines the tradeoff between frequency tuning range (12% to 25%) and radiation efficiency (45% to 55%).