DSpace Collection:
http://hdl.handle.net/2117/658
20150525T05:37:31Z

Stochastic estimation of the Frobenius norm in the ACA convergence criterion
http://hdl.handle.net/2117/27519
Title: Stochastic estimation of the Frobenius norm in the ACA convergence criterion
Authors: Heldring, Alexander; Úbeda Farré, Eduard; Rius Casals, Juan Manuel
Abstract: 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

Frequency, radiation pattern and polarization reconfigurable antenna using a parasitic pixel layer
http://hdl.handle.net/2117/27121
Title: Frequency, radiation pattern and polarization reconfigurable antenna using a parasitic pixel layer
Authors: Rodrigo López, Daniel; Cetiner, Bedri Artug
Abstract: 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

RF MEMS reconfigurable twoband antenna
http://hdl.handle.net/2117/26820
Title: RF MEMS reconfigurable twoband antenna
Authors: Zohur, Abdul; Mopidevi, Hema Swaroop; Rodrigo López, Daniel; Unlu, M.; Jofre Roca, Lluís; Cetiner, Bedri Artug
20150318T16:33:24Z

Design guidelines for a terahertz silicon microlens antenna
http://hdl.handle.net/2117/26819
Title: Design guidelines for a terahertz silicon microlens antenna
Authors: Alonso del Pino, María; Llombart, Núria; Chattopadhyay, G.; Lee, Craig; Jung Kubiak, Cecile; Jofre Roca, Lluís; Mehdi, Imran
Abstract: A silicon lens antenna suited for future integrated terahertz arrays has been proposed recently. The antenna consists of an extended hemispherical silicon lens fed by a leakywave waveguide feed. The primary advantage is that the antenna is compatible with silicon microfabrication techniques as only a small sector of the lens is actually used. Moreover, it can be easily integrated with other silicon micromachined frontend components. In this letter, the design and optimization details of such a microlens antenna is presented. The design is validated with a set of measurements at 550 GHz from a prototype that has been fabricated using laser microfabrication.
20150318T16:31:22Z

Telefonía IP de banda ancha
http://hdl.handle.net/2117/26341
Title: Telefonía IP de banda ancha
Authors: Elias Fusté, Antonio
Abstract: La telefonía IP representará una auténtica revolución, la primera en 100 años de telefonía vocal fija. A
nuestro entender, las dos palabras clave que definen los servicios de VoIP son: (1) “personalización”, concepto que empezamos a apreciar con la telefonía móvil y que se va a extender con las aplicaciones que ya acompañan y que sin duda se van a ampliar en los servicios de VoIP, servicios que conjuntados con aplicaciones de movilidad con redes de acceso WiFi o WiMax o con las mismas redes UMTS van a convertir definitivamente al terminal de VoIP en un periférico del cuerpo humano, que nos va a permitir romper definitivamente las barreras de espacio y tiempo en todo lo referente a comunicaciones personales. Y (2) separación plena entre el servicio telefónico y la red de acceso, tal comoocurre ahora con el correo electrónico.
20150213T13:25:11Z

Las Redes de nueva generación
http://hdl.handle.net/2117/26340
Title: Las Redes de nueva generación
Authors: Elias Fusté, Antonio
Abstract: Las redes de nueva generación (NGN) van a obligar a concebir un nuevo tipo de regulación.
20150213T13:14:01Z

El Ingeniero desde el concepto de servicio
http://hdl.handle.net/2117/26339
Title: El Ingeniero desde el concepto de servicio
Authors: Elias Fusté, Antonio; Torres Torres, Francisco
Abstract: Las exigencias actuales del entorno laboral hacen que el periodo de formación de un ingeniero no acabe con la obtención de su título, sino que continúe de forma muy importante a lo largo de toda su vida profesional. La profesionalización de la docencia en todos sus niveles hace patente que la formación de carácter científicotécnico tenga que ser complementada con conocimientos de tipo social y gerencial, dando lugar a la llamada formación integral del ingeniero. Un punto de vista muy útil a la hora de planificar y desarrollar la carrera profesional del ingeniero es aquel por el cual se le define como un profesional que ofrece un servicio de ingeniería. Así, el ingeniero desarrolla su carrera profesional a medida que aumenta la calidad y cantidad de los servicios que es capaz de ofrecer a sus clientes (compañeros, superiores, departamentos, empresas, organismos oficiales, etc). El diagrama de bloques de la figura 1 explicita el hecho de que en la actualidad la Universidad se ha especializado en proveer un servicio a la sociedad consistente en la formación de ingenieros. Éste se ha revelado muy efectivo para dotar a los alumnos de una sólida base de conocimientos científicotécnicos y para potenciar ciertas aptitudes como la capacidad de abstracción, el pensamiento sistemático, la capacidad de análisis, etc. ; dejando sin embargo, aspectos formativos de tipo social y gerencial para el aprendizaje autodidacta o a cargo de las empresas, ya en una etapa postacadémica.
20150213T12:46:29Z

Internet i la seva governança
http://hdl.handle.net/2117/26137
Title: Internet i la seva governança
Authors: Elias Fusté, Antonio
Abstract: In just over fifteen years, the internet has become the vehicle
for and instrument that sustains the new social model we know
of as the “information society”. The internet is a service based
on a system of telecommunication networks of a different nature,
with various models of exploitation and under different
legal jurisdictions. To show the complexity of internet governance,
a view is presented from three perspectives: technical,
economic and social. The combination of the economic aspect
with the social leads to the need to find a balance in order to
integrate the “open service” (natural network) nature of the
internet, with good quality service provided in the supporting
telecom networks. The article proposes a distribution of a
network’s capacity that allows the aforementioned integration,
and the need for an independent international body to manage
internet governance.
20150128T12:38:16Z

Threedimensional microfabricated broadband patch antenna for wiGig applications
http://hdl.handle.net/2117/25126
Title: Threedimensional microfabricated broadband patch antenna for wiGig applications
Authors: Mopidevi, Hema Swaroop; Hurneli, H. V.; Cagatay, E.; Biyikli, N.; Imbert Villà, Marc; Romeu Robert, Jordi; Jofre Roca, Lluís; Cetiner, Bedri Artug
Abstract: The design, microfabrication, and characterization of a broadband patch antenna capable of covering the entire IEEE 802.11ad (WiGig) frequency band (5766 GHz) are presented in this letter. A conductorbacked (CB) coplanar waveguide (CPW)fed loop slot couples the energy to the patch antenna, resulting in a broad bandwidth. The feed circuitry along with the loop is formed on a quartz substrate (epsilon(r) = 3.9, tan delta = 0.0002 at 60 GHz), on top of which an SU8based threedimensional (3D) structure with air cavities is microfabricated. The patch metallization is deposited on top of this 3D structure. While the main role of the structure made out of SU8 material is to provide a mechanical support for the patch metallization, the antenna takes advantage of the air cavities underneath, thus resulting in an antenna substrate with a very low loss. This, in turn, improves the overall antenna performances. The simulated and measured impedance characteristics agree well, showing similar to 15% bandwidth. Also, the radiation pattern results demonstrate the integrity of radiation pattern with reasonably constant gain values (average similar to 6.4 dB) in the broadside direction over the entire WiGig band.
20141222T15:49:02Z

Passive acoustic method for aircraft states estimation based on the Doppler effect
http://hdl.handle.net/2117/24983
Title: Passive acoustic method for aircraft states estimation based on the Doppler effect
Authors: Martín Román, SaraRegina; Genesca, Meritxell; Romeu Robert, Jordi; Arcos Villamarín, Robert
Abstract: A passive acoustic method to locate moving sound sources is applied to maneuvering aircraft. The advantages of the method are that it is suitable for all kinds of aircraft, not only propellerdriven, and is not restricted to low height above the ground. Its applicability could be, for instance, to supplement aircraft noise monitoring systems or to supervise small airports' activities. The method is based on the relation between the relative Doppler effect observed from a set of at least seven microphone receivers, distributed in the airport surroundings, and the aircraft position and speed. The method requires knowledge of the position of the aircraft at the start of takeoff. The ambiguity function is used to calculate the relative Doppler stretch of the spectrum of the sound between pairs of microphones. The results of applying the ambiguity function are the inputs to a system of equations that relates the aircraft position and speed to the relative Doppler frequency stretches. This system of equations is solved using a genetic algorithm. The performance of the method was tested by computer simulation. The results showed that the location errors are of the same order of magnitude as the size of an average aircraft, even if the takeoff position is not accurately known.
20141210T13:39:40Z

On the convergence of the ACA algorithm for radiation and scattering problems
http://hdl.handle.net/2117/24654
Title: On the convergence of the ACA algorithm for radiation and scattering problems
Authors: Heldring, Alexander; Úbeda Farré, Eduard; Rius Casals, Juan Manuel
Abstract: The adaptive cross approximation (ACA) algorithm, when used to accelerate the numerical solution of integral equations for radiation and scattering problems, sometimes suffers from inaccuracies. These inaccuracies occur when the ACA convergence criterion, which is based on an approximation of the residual relative error, is prematurely satisfied. This paper identifies the two sources of this problem and proposes adaptations of the algorithm that remedy them.
20141110T17:44:02Z

A quadband antenna for public safety applications
http://hdl.handle.net/2117/24294
Title: A quadband antenna for public safety applications
Authors: Mopidevi, Hema Swaroop; Damgaci, T; Rodrigo López, Daniel; Jofre Roca, Lluís; Cetiner, Bedri Artug
Abstract: The design, fabrication, and characterization of a frequencyreconfigurable antenna for the United States Public Safety (PS) wireless communication applications are presented. This antenna is quadband operating in the PS bands220, 470, 800, and 4960 MHz. It is an electrically small antenna with calculated ka similar to 0.55 at 220 MHz. The antenna has two reconfigurable modes of operations. In mode 1, 220, 470, and 4960MHz bands are excited. Mode 2 provides operation over 800 and 4960MHz bands. This dynamic frequency reconfiguration is accomplished by two radio frequency microelectromechanical systems switches strategically located within the antenna architecture. The measured and simulated results for impedance and radiation characteristics agree well, where similar to 3%, 4%, 21%, and 17% fractional bandwidths have been measured in the four bands, respectively, while maintaining integrity of radiation pattern.
20141007T13:24:32Z

Nonconforming discretization of the electricfield integral equation for closed perfectly conducting objects
http://hdl.handle.net/2117/24163
Title: Nonconforming discretization of the electricfield integral equation for closed perfectly conducting objects
Authors: Úbeda Farré, Eduard; Rius Casals, Juan Manuel; Heldring, Alexander
Abstract: Galerkin implementations of the method of moments (MoM) of the electricfield integral equation (EFIE) have been traditionally carried out with divergenceconforming sets. The normalcontinuity constraint across edges gives rise to cumbersome implementations around junctions for composite objects and to less accurate implementations of the combined field integral equation (CFIE) for closed sharpedged conductors. We present a new MoMdiscretization of the EFIE for closed conductors based on the nonconforming monopolarRWG set, with no continuity across edges. This new approach, which we call
20140925T14:15:46Z

New graphical processing technique for fast shadowing computation in PO surface integral
http://hdl.handle.net/2117/23208
Title: New graphical processing technique for fast shadowing computation in PO surface integral
Authors: Rius Casals, Juan Manuel; Carbó Meseguer, Alexis; Bjerkemo, Jakob; Úbeda Farré, Eduard; Heldring, Alexander; Mallorquí Franquet, Jordi Joan; Broquetas Ibars, Antoni
Abstract: This paper presents a new graphical processing technique for fast computation of PO surface integral. In contrast with the original graphical processing approach introduced by the authors in 1993, the new one combines a novel shadowing computation algorithm together with the conventional facetbased Gordon's formula, instead of the pixelbased Asvestas' approximation. The resulting hybrid approach needs more CPU power for very complex radar targets, but is free from the pixel discretization noise inherent to graphical processing. It has the same accuracy as conventional Physical Optics computation, but shadowed facets detection is more than 10 times faster than with the most efficient alternative algorithms of O(N log N) computational cost. © 2014 IEEE.
20140612T13:33:08Z

Unit cell for frequencytunable beamscanning reflectarrays
http://hdl.handle.net/2117/23126
Title: Unit cell for frequencytunable beamscanning reflectarrays
Authors: Rodrigo López, Daniel; Jofre Roca, Lluís; Perruisseau Carrier, Julien
Abstract: A reflectarray cell able to dynamically control the reflection phase at a variable frequency is presented. This capability enables beamscanning reflectarrays with frequency reconfigurability, which is a novel capability with applications in frequencyhopping systems, cognitive radio and satellite communications. The proposed cell combines switching and variable impedance loading techniques to maximize the frequency range over which a large dynamic phase range can be obtained. Analytical and numerical approaches are used to design and optimize the reflecting cell, which uses two semiconductor RFswitches and one varactor. An analog phase range above 270 degrees is achieved over a 50% frequency range, from 1.88 GHz to 3.07 GHz, with flat losses of 0.8 dB. For an analog phase range of 180 degrees the cell achieves a 1: 2 frequency reconfiguration range. It is also verified that the cell preserves good performance, and in particular low crosspolarization, under oblique incidence as well. A fully operational cell was fabricated and measured, demonstrating good agreement with simulation results.
20140602T15:12:00Z