http://hdl.handle.net/2117/658 2013-05-26T05:54:58Z http://hdl.handle.net/2117/18353 Title: Determination of the overlap factor and its enhancement for medium-size tropospheric lidar systems: a ray-tracing approach Authors: Kumar, Dhiraj; Rocadenbosch Burillo, Francisco Abstract: The problem of overlap factor (OVF) computation and its near-range sensitivity for medium-size aperture ( f ∕ 10 , f ∕ 11 ) bi-axial tropospheric lidar systems using ray-tracing sim- ulation software is presented. The method revisits both detector and fiber optics coupling alter- natives at the telescope focal-plane along with the insertion of a field lens. A sensitivity analysis is carried out as a function of laser divergence, field lens, and detector/fiber positions, detector size, and the fiber ’ s core diameter and numerical aperture. The ray-tracing approach presented here is straightforward and a comparatively much simpler solution than analytical-based meth- ods. Parametric simulations are carried out to show that both approaches are coincident. Insertion of a field lens proves to be an elegant and low sensitivity solution for OVF enhancement, par- ticularly, in the near-range of the lidar 2013-03-15T15:03:19Z http://hdl.handle.net/2117/17647 Title: Study on aerosol properties over Madrid (Spain) by multiple instrumentation during SPALI10 lidar campaign Authors: Molero, Francisco; Sicard, Michaël; Navas Guzmán, Francisco; Preissler, J.; Amodeo, Aldo; Freudenthaler, Volker; Fernández, J.A.; Tomás Martínez, Sergio; Granados, M.; Wagner, F.; Giunta, Aldo; Mattis, I.; Pujadas, Manuel; Comerón Tejero, Adolfo; Alados Arboledas, Lucas; Guerrero Rascado, Juan Luis; D'Amico, Giuseppe; Lange, Diego; Kumar, Dhiraj; Pappalardo, Gelsomina; Giner Nos, Joaquín José; Muñoz Porcar, Constantino; Rocadenbosch Burillo, Francisco Abstract: Cuatro sistemas lidar Raman multifrecuencia (Madrid, Granada, Barcelona y Evora), tomaron medidas simultáneamente a un sistema de referencia (Potenza) para verificar su funcionamiento durante la campaña de intercomparación: SPALI10, (SPAin Lidar Intercomparison 2010) que tuvo lugar en Madrid entre el 18 de Octubre y el 5 de Noviembre de 2010. Estos sistemas lidar Raman multifrecuencia proporcionan propiedades ópticas de los aerosoles con resolución vertical. Los perfiles suministrados por los sistemas lidar se compararon con información complementaria proporcionada por otra instrumentación, tal como la distribución de tamaños de los aerosoles medida de manera continua a nivel de superficie o la caracterización de la columna de aerosoles 2013-02-12T09:56:33Z http://hdl.handle.net/2117/17182 Title: Efficient parametric characterization of the dynamic performance of an RFID IC Authors: Capdevila Cascante, Santiago; Jofre Roca, Lluís; Romeu Robert, Jordi; Bolomey, J.Ch Abstract: In this letter, a measurement technique for a complete parametric characterization of the input impedance of an RFID IC is presented. The use of an SPDT switch to modulate the signal from the network analyzer provides the capability to measure the RFID IC activation level and its input impedance simultaneously. This data can then be used to fully predict the dynamic response and performance of an RFID tag. 2012-12-20T15:50:02Z http://hdl.handle.net/2117/17174 Title: Parasitic layer-based reconfigurable antenna design by multi-objective optimization Authors: Yuan, Xiaoyan; Li, Zhouyuan; Rodrigo López, Daniel; Mopidevi, Hema Swaroop; Kaynar, Oguz; Jofre Roca, Lluís; Cetiner, Bedri Artug Abstract: A parasitic layer-based multifunctional reconfigurable antenna (MRA) design based on multi-objective genetic algorithm optimization used in conjunction with full-wave EM analysis is presented. TheMRA is capable of steering its beam into three different directions simultaneously with polarization reconfigurability having six different modes of operation. The MRA consists of a driven microstrip-fed patch element and a reconfigurable parasitic layer, and is designed to be compatible with IEEE-802.11 WLAN standards (5–6 GHz range). The parasitic layer is placed on top of the driven patch. The upper surface of the parasitic layer has a grid of 5 5 electrically small rectangular-shaped metallic pixels, i.e., reconfigurable parasitic pixel surface. The EM energy from the driven patch element couples to the reconfigurable parasitic pixel surface by mutual coupling. The adjacent pixels are connected/disconnected by means of switching, thereby changing the geometry of pixel surface, which in turn changes the current distribution over the parasitic layer, results in the desired mode of operation in beam direction and polarization. A prototype of the designed MRA has been fabricated on quartz substrate. The results from simulations and measurements agree well indicating 8 dB gain in all modes of operation. 2012-12-20T13:50:33Z http://hdl.handle.net/2117/17173 Title: Fabrication and measurement of homemade standard antennas Authors: Guardiola Garcia, Marta; Monsalve Carcelen, Beatriz; Calafell Rueda, Irena; Roqueta Crusats, Gemma; Romeu Robert, Jordi Abstract: Apprenticeship is linked to training. This paper is intended to be a tutorial on how to design, fabricate, and measure antennas in an economical and easy way, using recycled materials and common electronic devices such as a laptop and an access point. Several antenna designs built with household materials are proposed, giving practical design and fabrication guidelines. The use of the Wi-Fi band allows linking the experiment with daily-life devices, and proposing a simple and economical antenna-measurement system. The capacity to experiment with antennas from their design to measurement will defi nitely stimulate undergraduate or graduate students to get acquainted with the basic topics of antennas and propagation. The paper presented herein was awarded with the fi rst price in the IEEE AP-S Student Challenge 2010 [1, 2]. 2012-12-20T13:45:45Z http://hdl.handle.net/2117/17163 Title: Frequency and radiation pattern reconfigurability of a multi-size pixel antenna Authors: Rodrigo López, Daniel; Jofre Roca, Lluís Abstract: Pixel reconfigurable apertures constitute one of the most adaptable structures regarding antenna reconfiguration, being capable to achieve frequency and pattern compound reconfiguration. However, pixel antennas require a large amount of switches (typically above 100) that severely impact the antenna efficiency, complexity, cost and reconfiguration time. This paper presents a novel technique to mitigate the inherent complexity of pixel antennas by including multiple sized pixels divided over driven and parasitic regions. The technique has been applied to a planar monopole architecture leading to a low-complexity prototype of small dimensions and requiring only 12 switches. Its reconfiguration properties have been fully characterized through exhaustive measurements. Frequency reconfiguration is achieved from 1 GHz to 6 GHz with simultaneous beam-steering capabilities, being capable of synthesizing at each frequency an omnidirectional pattern and up to 5 directive patterns steered towards directions covering an angular range of almost 180 . 2012-12-19T18:50:13Z http://hdl.handle.net/2117/17160 Title: Circular beam-steering reconfigurable antenna with liquid metal parasitics Authors: Rodrigo López, Daniel; Jofre Roca, Lluís; Cetiner, Bedri Artug Abstract: A novel antenna reconfiguration mechanism based on the displacement of liquid metal sections is presented. The liquid nature of the moving parts of the antenna helps avoid the main disadvantage of mechanically-actuated reconfigurable antennas which is the mechanical failure of their solid parts due to material fatigue, creep or wear. Furthermore, the displacement of liquid elements can be more effectively performed than in the case of solid materials by applying precise microfluidic techniques such as continuous-flow pumping or electrowetting. The reconfiguration mechanism is demonstrated through the design, fabrication and measurement of a radiation pattern reconfigurable antenna. This antenna operates at 1800 MHz with 4.0% bandwidth and is capable of performing beam-steering over a 360 range with fine tuning. The antenna is a novel circular Yagi-Uda array, where the movable parasitic director and reflector elements are implemented by liquid metal mercury (Hg). The parasitics are placed and rotated in a circular microfluidic channel around the driven element by means of a flow generated and controlled by a piezoelectric micropump. The measured results demonstrate good performance and the applicability of the microfluidic system. 2012-12-19T18:12:56Z http://hdl.handle.net/2117/16627 Title: Analysis of the electromagnetic signature of reinforced concrete structures for nondestructive evaluation of corrosion damage Authors: Roqueta Crusats, Gemma; Jofre Roca, Lluís; Feng, M.Q. Abstract: This paper presents a nondestructive corrosion damage detection method for reinforced concrete structures based on the analysis of the electromagnetic signature of the steel rebar corrosion. The signature of the corrosion on the scattered field upon microwave illumination is first numerically analyzed. First-order quality factor parameters, the energy and the mean propagation delay, are proposed to quantify the corrosion amount in the structure. To validate the model, low-profile ultra-wide-band antennas (3–12 GHz) are fabricated and measured. Measurements on 12 reinforced concrete samples with induced corrosion are performed, using three different antenna setups. The experiments demonstrate a good correlation between an increase in the corrosion amount with a decrease in the energy and an increase in the time delay of the propagated signal. 2012-10-03T18:22:01Z http://hdl.handle.net/2117/16584 Title: Silicon micro-lens antennas for THz integrated arrays Authors: Alonso, M.; Llombart, Nuria; Lee, Clement; Jung, C.; Chattopadhyay, G.; Jofre Roca, Lluís; Mehdi, Imran Abstract: In this paper, we describe the characterization of silicon micro-lenses fabricated by two different techniques, one using laser micromachining and the other developed using photolithographical techniques. The micro-lens antenna patterns were measured from 530 to 600 GHz and the characteristics of the two lenses compared. 2012-09-26T11:58:19Z http://hdl.handle.net/2117/16079 Title: Signal-to-noise ratio equalization for TOPSAR mode using a nonuniform steering rate Authors: Ruiz Rodon, Josep; Broquetas Ibars, Antoni; González Arbesú, José María; Closa Domínguez, Josep M.; Labriola, M Abstract: In this letter, an optimized scanning in terrain observation by progressive scan synthetic aperture radar (TOPSAR) mode is studied. A nonuniform steering rate of the radar array antenna in the along-track direction is proposed in order to obtain constant radiometric sensitivity and signal-to-noise ratio. This is achieved owing to the longer integration time of the echoes received at both ends of the antenna azimuth sweep. By optimizing iteratively the array discrete steering rate law, the radiometric impact of the array basic element pattern (subarray pattern) can be accurately compensated. First, simulation results are presented to validate the nonuniform steering TOPSAR. 2012-06-18T14:21:02Z http://hdl.handle.net/2117/16060 Title: Isofrequency-reconfigurable 8-bit RF repeater Authors: Díaz Tapia, Edgar; Grau, Alfred; Rodriguez De Luis, Javier; de Flaviis, Franco; Jofre Roca, Lluís Abstract: A novel isofrequency-reconfigurable RF repeater operating at 4.5 GHz is presented. The repeater uses a total of eight reconfigurable parasitic dipole elements to enhance and reconfigure the isolation level between the receiving (Rx) and the transmiting (Tx) antennas. The reconfiguration of the parasitic dipoles is achieved using p-i-n diodes as microwave switches to change their electrical length. The parasitic dipoles are dynamically reconfigured into an optimum configuration state (to make them work as either director or reflector elements) to enhance and recover the perturbed isolation level when an obstacle is placed near the repeater, while maintaining good impedance matching and pointing the maximum of the radiation pattern at the Rx port toward a specific base station. 2012-06-15T16:48:37Z http://hdl.handle.net/2117/14984 Title: Concentric annular-ring microstrip antenna with circular polarization Authors: Ramirez, M.; Parrón, Josep; González Arbesú, José María; Gemio, J. Abstract: In this letter,we present a concentric annular-ring microstrip antenna that covers the bands of Galileo (E5a, E5b, E1, E2, L1), GPS (L1, L2, L5), and GLONASS (L1, L3). This microstrip antenna is fed by four apertures that improve the coupling. Broadband phase shifters and Wilkinson power combiners are used to generate the required circular polarization. 2012-02-06T18:32:09Z http://hdl.handle.net/2117/14785 Title: Portafolio digital de aprendizaje: un nuevo medio de comunicación en la educación Authors: Coromina, Judit; Sabaté i Garriga, Ferran; Romeu Robert, Jordi; Ruiz, Ferran Abstract: Propósito: La Generalitat de Catalunya tiene previsto introducir antes del año 2017 el portafolio digital, una iniciativa vinculada con los nuevos métodos de aprendizaje. Constatado el creciente interés por el portafolio digital como medio de comunicación en la educación, este artículo tiene por objetivos describir detalladamente su funcionamiento e identificar una lista de criterios, útiles a los centros educativos, para seleccionar la aplicación de gestión del portafolio digital que mejor se adapte a sus necesidades. Diseño/metodología/enfoque: En primer lugar se fija el marco teórico de funcionamiento del portafolio digital. Luego se tipifican las aplicaciones que son usadas comúnmente para su implementación. A continuación se realiza un análisis de requisitos de una aplicación ideal con acuerdo a las fases de creación del portafolio identificados en el marco teórico. Finalmente, a partir de estos requisitos se identifica una lista de criterios útiles para seleccionar la aplicación de soporte al portafolio. Resultados y originalidad/valor: El artículo aporta un proceso estructurado en etapas y fases para la creación del portafolio digital que va más allá de los existentes en la literatura. Además, define una lista de criterios útiles para seleccionar la aplicación de soporte al portafolio digital que más convenga a un centro educativo, obtenidos con una metodología bastante exhaustiva. Limitaciones/implicaciones de investigación: Para poner en práctica los criterios identificados se propone completar, en un nuevo estudio, el modelo de decisión multicriterio, especificando los procesos para pesar los criterios y normalizarlos. Después se podría analizar la validez del modelo estudiando la satisfacción obtenida por su uso en una muestra de centros educativos. Implicaciones prácticas: La lista de criterios se espera facilite la selección de la aplicación informática de soporte al portafolio de aprendizaje a los centros educativos, con acuerdo a sus necesidades específicas. 2012-01-24T16:30:01Z http://hdl.handle.net/2117/13361 Title: Taylor-orthogonal basis functions for the discretization in method of moments of second kind integral equations in the scattering analysis of perfectly conducting or dielectric objects Authors: Úbeda Farré, Eduard; Tamayo Palau, José María; Rius Casals, Juan Manuel Abstract: We present new implementations in Method of Moments of two types of second kind integral equations: (i) the recently proposed Electric-Magnetic Field Integral Equation (EMFIE), for perfectly conducting objects, and (ii) the Müller formulation, for homogeneous or piecewise homogeneous dielectric objects. We adopt the Taylor-orthogonal basis functions, a recently presented set of facet-oriented basis functions, which, as we show in this paper, arise from the Taylor's expansion of the current at the centroid of the discretization triangles. We show that the Taylor-orthogonal discretization of the EMFIE mitigates the discrepancy in the computed Radar Cross Section observed in conventional divergence-conforming implementations for moderately small, perfectly conducting, sharp-edged objects. Furthermore, we show that the Taylor-discretization of the Müller-formulation represents a valid option for the analysis of sharp-edged homogenous dielectrics, especially with low dielectric contrasts, when compared with other RWG-discretized implementations for dielectrics. Since the divergence-Taylor Orthogonal basis functions are facet-oriented, they appear better suited than other, edge-oriented, discretization schemes for the analysis of piecewise homogenous objects since they simplify notably the discretization at the junctions arising from the intersection of several dielectric regions. 2011-09-27T12:44:22Z http://hdl.handle.net/2117/13274 Title: A recursive acceleration technique for static potential Green's functions of a rectangular cavity combining image and modal series Authors: Tamayo Palau, José María; López-Peña, Sergio; Mattes, Michael; Heldring, Alexander; Rius Casals, Juan Manuel; Mosig, Juan Ramón Abstract: A hybrid acceleration algorithm for the computation of the static potential Green’s functions of a rectangular cavity is proposed. Similarly to Ewald’s method, it combines the series expansions in terms of images and modes. The main particularity with respect to Ewald resides in the fact that it does not need the evaluation of a nonalgebraic function such as the complementary error function (erfc) while maintaining the rapid convergence of the Ewald technique. Finally, the method requires the computation of eight terms (original source plus seven images) and of several modal series corresponding to bigger cavities, which can be efficiently performed. Numerical results are provided to verify the feasibility of the algorithm, which appears as a promising alternative to the existing methods in the literature. 2011-09-20T13:18:17Z