Desfasador de dos estats

El projecte es basa en el disseny i la fabricació d’un circuit desfasador, amb una entrada i una sortida, que commuta entre dos estats, un estat amb desfasament de 180º i l’altre sense desfasament. El circuit es dissenya amb microstrip,per una fc=5GHz. S’intenten obtenir les millors característiques per aquest disseny, és a dir, bon ample de banda i pèrdues per inserció baixes, acompanyat d’una bona resposta en les relacions de magnitud i fase. Es segueixen diferents etapes de disseny, on es comença per un model simple i s’avança en complexitat, afegint els nous components que acabaran conformant el circuit final. Després del disseny es passa a la fabricació del circuit, per veure el seu funcionament real. La memòria recull i ordena la informació obtinguda a través d’aquest procés, intentant mostrar-la de manera clara, per tal de seguir el procés de disseny realitzat, i així poder interpretar els resultats obtinguts. L’objectiu final és veure com es comporta el circuit dissenyat i definir les pautes a seguir per millorar-lo en un futur.

Control of optical fields and single photon emitters by advanced nanoantenna structures

The control of optical fields on the nanometre scale is becoming an increasingly important tool in many fields, ranging from channelling light delivery in photovoltaics and light emitting diodes to increasing the sensitivity of chemical sensors to single molecule levels. The ability to design and manipulate light fields with specific frequency and space characteristics is explored in this project. We present an alternative realisation of Extraordinary Optical Transmission (EOT) that requires only a single aperture and a coupled waveguide. We show how this waveguide-resonant EOT improves the transmissivity of single apertures. An important technique in imaging is Near-Field Scanning Optical Microscopy (NSOM); we show how waveguide-resonant EOT and the novel probe design assist in improving the efficiency of NSOM probes by two orders of magnitude, and allow the imaging of single molecules with an optical resolution of as good as 50 nm. We show how optical antennas are fabricated into the apex of sharp tips and can be used in a near-field configuration.

Caracterización de materiales en banda W

Para medir los coeficientes de transmisión y reflexión, S21 y S11, de diferentes materiales o muestras planas, se usa un sistema de toma de medidas en espacio libre operando banda W (75 – 110 GHz). Usando estos parámetros, S21 y S11, podemos calcular la permitividad dieléctrica relativa compleja (Er ) y la permeabilidad magnética relativa compleja (μr) mediante un proceso llamado NRW (Nicolson-Ross-Weir). El sistema para medir consiste en dos antenas de bocina, una transmisora y otra receptora, dos espejos con los que obtenemos una onda plana para medir las propiedades del material y un ordenador o dispositivo que calcula los resultados. Este dispositivo requiere de calibración para la obtención de resultados óptimos. Dicho sistema se puede simular de manera ideal con un software llamado ADS (Assistance Design System) para el estudio y comparación de grosores, permitividades dieléctricas relativas y permeabilidades magnéticas relativas de los materiales en función de la frecuencia.

Estudio de parámetros circuitales de resonadores

El objetivo de este proyecto consiste en el estudio de los parámetros circuitales (condensadores, bobinas…) de un resonador, realizado con estructuras microstrip, donde permita obtener unos resultados de esos parámetros circuitales cambiando los valores físicos del diseño, tales como la longitud y la anchura del resonador a partir de las medidas de los parámetros S. Para llevar a cabo dicho trabajo, se desarrolla en primer lugar toda la teoría necesaria de resonadores. Empezando por el funcionamiento y la estructura del resonador diseñado, y mostrando especial interés en el modelado de dicho resonador. Seguidamente, se estudia y analiza su comportamiento a través de las simulaciones de los parámetros S. Una vez se ha estudiado y analizado su comportamiento, se procede con las modificaciones de los parámetros físicos y se analiza a través de las simulaciones de los parámetros S cómo afectan estas modificaciones en los parámetros circuitales. Donde se utilizan una serie de herramientas que agilizan la extracción de los valores de los parámetros circuitales del resonador.

Metodologia per a la generació de consens social en el desplegament d'infraestructures de telefonia mòbil

Aquest document de treball es centra específicament en el desenvolupament de la infraestructura de telefonia mòbil a Catalunya com a exemple de tecnologia amb profundes implicacions socials. Esdevé un intent inicial de definir les principals línies de recerca en aquest tema. El projecte que el sosté és emmarcat en el programa de recerca Negrisc, centrat a examinar la negociació del risc en les tecnologies de la informació i de la comunicació. Parteix d'una aproximació que reconeix la natura multidisciplinària del risc i que, per tant, exigeix una aproximació interdisciplinària al seu estudi i a la gestió subsegüent. Aquesta perspectiva emfatitza la necessitat d'integrar els punts de vista dels diferents stakeholders, incloent-hi el públic, en la gestió d'una tecnologia socialment controvertida. Aquest és un pas necessari per a permetre la generació d'algun tipus de consens en el cas del desenvolupament de la infraestructura de telefonia mòbil a Catalunya.

A new approach to real time traffic sign recognition based on colour information

The automatic interpretation of conventional traffic signs is very complex and time consuming. The paper concerns an automatic warning system for driving assistance. It does not interpret the standard traffic signs on the roadside; the proposal is to incorporate into the existing signs another type of traffic sign whose information will be more easily interpreted by a processor. The type of information to be added is profuse and therefore the most important object is the robustness of the system. The basic proposal of this new philosophy is that the co-pilot system for automatic warning and driving assistance can interpret with greater ease the information contained in the new sign, whilst the human driver only has to interpret the "classic" sign. One of the codings that has been tested with good results and which seems to us easy to implement is that which has a rectangular shape and 4 vertical bars of different colours. The size of these signs is equivalent to the size of the conventional signs (approximately 0.4 m2). The colour information from the sign can be easily interpreted by the proposed processor and the interpretation is much easier and quicker than the information shown by the pictographs of the classic signs

Estudi de nusos rígids prefabricats de formigó

Una de les principals limitacions de les edificacions industrialitzades resoltes amb prefabricat de formigó, és que els nusos que defineixen les interseccions dels seus elements són articulacions, provocant diferències importants del model estructural d’una obra resolta “in situ” on els nusos poden ser considerats encastaments elàstics. Aquest projecte proposa fer un pas més en aquesta limitació exposada i plantejar sistemes de nusos rígids, resolts amb el propi prefabricat que permetin variar el model de nusos articulats a rígids. Això augmentarà el grau d’hiperestaticitat de l’estructura, redistribuint els esforços en els seus elements, disminuint les deformacions i les longituds de vinclament dels pilars. L’objecte del treball és definir la millora que aporta la utilització de nusos rígids en el càlcul estructural, basada en una disminució de sol·licitacions al llarg del pilar, possibilitat de reducció de secció de pilars, reducció de l’armadura necessària en pilars i jàsseres, i finalment, un estalvi econòmic. Partirem d’un edifici d’habitatges d’ús residencial PB+3 de planta rectangular de 24·11 m i de 13,5 m d’altura. Aquesta tipologia d’edifici serà el punt de partida per al plantejament, sobre d’aquesta base, de 3 models estructurals diferents, amb la intenció de satisfer de forma raonada i minuciosa 3 plantejaments estàticament diferents

Dipolo impreso para aplicaciones Wi-fi y caracterización de la ganancia por medio de la celda TEM

Este trabajo recoge el estudio, diseño, fabricación y análisis de dos dipolos de media onda para aplicaciones Wi-fi, con objeto de caracterizar sus respectivas ganancias mediante el uso de dos sistemas de medida distintos, el primero basado en el análisis del balance de enlace entre antenas mediante un analizador de redes y el segundo mediante una celda TEM. Para obtener un correcto funcionamiento de los dipolos, resulta de vital importancia conseguir un buen ajuste de las dimensiones de los mismos durante el desarrollo práctico del proyecto, consiguiendo una máxima transferencia de potencia y un ancho de banda suficientemente amplio para asegurar que las antenas presenten una buena adaptación en la banda de los 2.4 GHz – 2.5 GHz.

Nuevo disipador para edificación sismorresistente. 1ª parte: caracterización y modelos de predicción

A new energy dissipator, based on yielding of steel under shear response, has been developed and recently tested. It is H shaped and web stiffened. Yielding moin part is mechanized from one piece of rectangular shoped steel bar. Its conception let obtain thin and well-stiffened web cross sections without welded parts. Main experimentally obtained charecteristics are a yielding point near 0.5 mm of displacement, yielding loads between 14 kN and 20 kN and a dissipated energy, before damage appears in the web, from 10 kJ to 21 kJ. All tested specimens have developed large deformations without web buckling. Whe web degradation appers, flanges and stiffeners keep dissipating an important amount of energy. Proposed numerical models and simple mathematical expressions offer well correlated results when compared to the experimental ones

A unified treatment of optimum pilot overhead in multipath fading channels

The optimization of the pilot overhead in single-user wireless fading channels is investigated, and the dependence of this overhead on various system parameters of interest (e.g., fading rate, signal-to-noise ratio) is quantified. The achievable pilot-based spectral efficiency is expanded with respect to the fading rate about the no-fading point, which leads to an accurate order expansion for the pilot overhead. This expansion identifies that the pilot overhead, as well as the spectral efficiency penalty with respect to a reference system with genie-aided CSI (channel state information) at the receiver, depend on the square root of the normalized Doppler frequency. It is also shown that the widely-used block fading model is a special case of more accurate continuous fading models in terms of the achievable pilot-based spectral efficiency. Furthermore, it is established that the overhead optimization for multiantenna systems is effectively the same as for single-antenna systems with the normalized Doppler frequency multiplied by the number of transmit antennas.

Impact of antenna correlation on the capacity of multiantenna channels

This paper applies random matrix theory to obtain analytical characterizations of the capacity of correlated multiantenna channels. The analysis is not restricted to the popular separable correlation model, but rather it embraces a more general representation that subsumesmost of the channel models that have been treated in the literature. For arbitrary signal-to-noise ratios (SNR), the characterization is conducted in the regime of large numbers of antennas. For the low- and high-SNR regions, in turn, we uncover compact capacity expansions that are valid for arbitrary numbers of antennas and that shed insight on how antenna correlation impacts the tradeoffs between power, bandwidth and rate.

High-SNR power offset in multiantenna communication

The analysis of the multiantenna capacity in the high-SNR regime has hitherto focused on the high-SNR slope (or maximum multiplexing gain), which quantifies the multiplicative increase as function of the number of antennas. This traditional characterization is unable to assess the impact of prominent channel features since, for a majority of channels, the slope equals the minimum of the number of transmit and receive antennas. Furthermore, a characterization based solely on the slope captures only the scaling but it has no notion of the power required for a certain capacity. This paper advocates a more refined characterization whereby, as function of SNRjdB, the high-SNR capacity is expanded as an affine function where the impact of channel features such as antenna correlation, unfaded components, etc, resides in the zero-order term or power offset. The power offset, for which we find insightful closed-form expressions, is shown to play a chief role for SNR levels of practical interest.

Capacity-achieving input covariance for single-user multi-antenna channels

We characterize the capacity-achieving input covariance for multi-antenna channels known instantaneously at the receiver and in distribution at the transmitter. Our characterization, valid for arbitrary numbers of antennas, encompasses both the eigenvectors and the eigenvalues. The eigenvectors are found for zero-mean channels with arbitrary fading profiles and a wide range of correlation and keyhole structures. For the eigenvalues, in turn, we present necessary and sufficient conditions as well as an iterative algorithm that exhibits remarkable properties: universal applicability, robustness and rapid convergence. In addition, we identify channel structures for which an isotropic input achieves capacity.

Capacity-approaching rate function for layered multiantenna architectures

The simultaneous use of multiple transmit and receive antennas can unleash very large capacity increases in rich multipath environments. Although such capacities can be approached by layered multi-antenna architectures with per-antenna rate control, the need for short-term feedback arises as a potential impediment, in particular as the number of antennas—and thus the number of rates to be controlled—increases. What we show, however, is that the need for short-term feedback in fact vanishes as the number of antennas and/or the diversity order increases. Specifically, the rate supported by each transmit antenna becomes deterministic and a sole function of the signal-to-noise, the ratio of transmit and receive antennas, and the decoding order, all of which are either fixed or slowly varying. More generally, we illustrate -through this specific derivation— the relevance of some established random CDMA results to the single-user multi-antenna problem.

Sequential estimation of multipath MIMO-OFDM channels

Wireless “MIMO” systems, employing multiple transmit and receive antennas, promise a significant increase of channel capacity, while orthogonal frequency-division multiplexing (OFDM) is attracting a good deal of attention due to its robustness to multipath fading. Thus, the combination of both techniques is an attractive proposition for radio transmission. The goal of this paper is the description and analysis of a new and novel pilot-aided estimator of multipath block-fading channels. Typical models leading to estimation algorithms assume the number of multipath components and delays to be constant (and often known), while their amplitudes are allowed to vary with time. Our estimator is focused instead on the more realistic assumption that the number of channel taps is also unknown and varies with time following a known probabilistic model. The estimation problem arising from these assumptions is solved using Random-Set Theory (RST), whereby one regards the multipath-channel response as a single set-valued random entity.Within this framework, Bayesian recursive equations determine the evolution with time of the channel estimator. Due to the lack of a closed form for the solution of Bayesian equations, a (Rao–Blackwellized) particle filter (RBPF) implementation ofthe channel estimator is advocated. Since the resulting estimator exhibits a complexity which grows exponentially with the number of multipath components, a simplified version is also introduced. Simulation results describing the performance of our channel estimator demonstrate its effectiveness.