Contribution to the Analysis, Design and Assessment of Compact Antenna Test Ranges At Millimeter Wavelengths - Contribución al Análisis, Diseño y Caracterización de Sistemas de Medida de Antenas en Rango Compacto para Frecuencias Milimétricas

This Doctoral Thesis entitled Contribution to the analysis, design and assessment of compact antenna test ranges at millimeter wavelengths aims to deepen the knowledge of a particular antenna measurement system: the compact range, operating in the frequency bands of millimeter wavelengths. The thesis has been developed at Radiation Group (GR), an antenna laboratory which belongs to the Signals, Systems and Radiocommunications department (SSR), from Technical University of Madrid (UPM). The Radiation Group owns an extensive experience on antenna measurements, running at present four facilities which operate in different configurations: Gregorian compact antenna test range, spherical near field, planar near field and semianechoic arch system. The research work performed in line with this thesis contributes the knowledge of the first measurement configuration at higher frequencies, beyond the microwaves region where Radiation Group features customer-level performance. To reach this high level purpose, a set of scientific tasks were sequentially carried out. Those are succinctly described in the subsequent paragraphs. A first step dealed with the State of Art review. The study of scientific literature dealed with the analysis of measurement practices in compact antenna test ranges in addition with the particularities of millimeter wavelength technologies. Joint study of both fields of knowledge converged, when this measurement facilities are of interest, in a series of technological challenges which become serious bottlenecks at different stages: analysis, design and assessment. Thirdly after the overview study, focus was set on Electromagnetic analysis algorithms. These formulations allow to approach certain electromagnetic features of interest, such as field distribution phase or stray signal analysis of particular structures when they interact with electromagnetic waves sources. Properly operated, a CATR facility features electromagnetic waves collimation optics which are large, in terms of wavelengths. Accordingly, the electromagnetic analysis tasks introduce an extense number of mathematic unknowns which grow with frequency, following different polynomic order laws depending on the used algorithmia. In particular, the optics configuration which was of our interest consisted on the reflection type serrated edge collimator. The analysis of these devices requires a flexible handling of almost arbitrary scattering geometries, becoming this flexibility the nucleus of the algorithmia’s ability to perform the subsequent design tasks. This thesis’ contribution to this field of knowledge consisted on reaching a formulation which was powerful at the same time when dealing with various analysis geometries and computationally speaking. Two algorithmia were developed. While based on the same principle of hybridization, they reached different order Physics performance at the cost of the computational efficiency. Inter-comparison of their CATR design capabilities was performed, reaching both qualitative as well as quantitative conclusions on their scope. In third place, interest was shifted from analysis - design tasks towards range assessment. Millimetre wavelengths imply strict mechanical tolerances and fine setup adjustment. In addition, the large number of unknowns issue already faced in the analysis stage appears as well in the on chamber field probing stage. Natural decrease of dynamic range available by semiconductor millimeter waves sources requires in addition larger integration times at each probing point. These peculiarities increase exponentially the difficulty of performing assessment processes in CATR facilities beyond microwaves. The bottleneck becomes so tight that it compromises the range characterization beyond a certain limit frequency which typically lies on the lowest segment of millimeter wavelength frequencies. However the value of range assessment moves, on the contrary, towards the highest segment. This thesis contributes this technological scenario developing quiet zone probing techniques which achieves substantial data reduction ratii. Collaterally, it increases the robustness of the results to noise, which is a virtual rise of the setup’s available dynamic range. In fourth place, the environmental sensitivity of millimeter wavelengths issue was approached. It is well known the drifts of electromagnetic experiments due to the dependance of the re sults with respect to the surrounding environment. This feature relegates many industrial practices of microwave frequencies to the experimental stage, at millimeter wavelengths. In particular, evolution of the atmosphere within acceptable conditioning bounds redounds in drift phenomena which completely mask the experimental results. The contribution of this thesis on this aspect consists on modeling electrically the indoor atmosphere existing in a CATR, as a function of environmental variables which affect the range’s performance. A simple model was developed, being able to handle high level phenomena, such as feed - probe phase drift as a function of low level magnitudes easy to be sampled: relative humidity and temperature. With this model, environmental compensation can be performed and chamber conditioning is automatically extended towards higher frequencies. Therefore, the purpose of this thesis is to go further into the knowledge of millimetre wavelengths involving compact antenna test ranges. This knowledge is dosified through the sequential stages of a CATR conception, form early low level electromagnetic analysis towards the assessment of an operative facility, stages for each one of which nowadays bottleneck phenomena exist and seriously compromise the antenna measurement practices at millimeter wavelengths.

Array Compacto De Monopolos Planos Con Plano De Tierra Ranurado Para Sistemas Mimo

A compact array of monopoles with a slotted ground plane is analyzed for being used in MIMO systems. Compact arrays suffer usually from high coupling which degrades significantly MIMO benefits. Through a matching network, main drawbacks can be solved, although it tends to provide a low bandwidth. The studied design is an array of monopoles with a slot in the ground plane. The slot shape is optimized with a Genetic Algorithm and an own electromagnetic software based on MoM in order to fulfill main figures of merit within a significant bandwidth

Trabajos virtuales. Un método compacto para el análisis práctico

La utilización del teorema de los trabajos virtuales para el estudio de los mecanismos de colapso de una estructura, permite resolver con elegancia y sencillez los problemas de diseño práctico. En este artículo se recuerdan los conceptos fundamentales y se resuelven algunos ejemplos.

Evaluación de procesos de desgaste en turbinas aeronáuticas mediante espectrometría por disco rotativo(rde) y por contador de partículas láser(lnf)

En esta ponencia se realiza una revisión de diferentes metodologías para la evaluación de procesos de desgaste en turbinas aéreas derivadas. Mediante el análisis de las características del lubricante utilizado, a través de espectrometría de micropartículas y de la evaluación por contadores de partículas de tamaño superior a los 20 micrómetros, se pretende determinar procesos de desgaste y correlaciones entre diversos parámetros de funcionamiento de la turbina. Para ello se presentan las principales metodologías de análisis de aceite en uso, indicando la información que suministran, los ámbitos en los que su aplicación es pertinente, y se muestran los resultados de diferentes casos de aplicación correspondientes tanto a aeronaves de ala fija como de ala rotativa.

Sistema de adquisición de datos compacto para medidas de extensiometría y posición

En este proyecto se trata el diseño y construcción de un sistema de adquisición de datos compacto y de bajo coste para medidas de extensiometría y posición. Dicho sistema irá embarcado en una bicicleta de montaña con el fin de medir determinados parámetros. Estos parámetros son a) Elongación de las suspensiones, b) Deformación en el cuadro. Para la medida de elongación de las suspensiones se diseña y construye un sensor casero de bajo coste basado en una transparencia y un par de diodos fotoemisor y fotorreceptor infrarrojos. Se imprime un gradiente y se emplean dos tubos coaxiales de PVC. La medida de extensiometría se realiza con galgas extensiométricas, puentes de Wheatstone y amplificador de instrumentación. Las muestras se digitalizan con el ADC del microcontrolador C8051F020 de la casa Silabs, que se usa en una placa de desarrollo, y se almacenan en una memoria flash serie. Se desarrolla un software para PC con LabView para poder recibir, procesar y visualizar las muestras obtenidas de los distintos canales con el fin de analizarlas. Se obtienen conclusiones de los resultados de pruebas básicas. ABSTRACT On this project, the design and construction of a compact, low cost, data adquisition system for strain and position measurements is dealt with. Such system will be embedded on a bicycle in order to measure certain parameters. These are a) Suspension elongation, b) Frame deformation. For suspension elongation measurements, a homemade, low cost sensor based on a photoemitter-photoreceiver diode couple and a transparent sheet is designed and built. A gradient is printed in the transparent sheet, and two coaxial PVC pipes are used. Strain measurements are carried out by means of a strain gage, Wheatstone bridges and an instrumentation amplifier. Samples are digitized with Silabs’ C8051F020’s ADC, which is used in a development board, and are stored in a serial flash memory. Software for PC on LabView is developed in order to receive, process and visualize the obtained samples from each channel in order to analyze them. Results are obtained from basic tests.

Desarrollo de una aplicación web para la reducción de ruido del sonido grabado de un disco de vinilo

Las grabaciones digitales de discos de vinilo, al ser un medio de almacenamiento de sonido analógico, están afectadas por ruido de diversos tipos, debido al deterioro de la superficie con el tiempo y con su reproducción. Aunque algunos programas de edición de audio permiten hacer una reducción de ruido sobre esas grabaciones, muchos consumidores de música en vinilo los desconocen, encuentran complicado su uso o quieren evitar la instalación de programas adicionales en su ordenador. Este proyecto consiste en el desarrollo de una aplicación web que pretende acabar con estos impedimentos y ofrecer un medio sencillo y eficaz para la reducción de ruido, ejecutable a través de un navegador, que simplifique el proceso de cara al usuario. El funcionamiento es sencillo: un usuario sube un archivo de audio al servidor, éste lo procesa y lo devuelve al cliente. El servidor, en la fase de procesamiento de señal, realiza una reducción de ruido mediante una puerta de ruido en el dominio de la frecuencia, desarrollada en lenguaje Python, y diseñada en función de un estudio previo de diversas muestras de ruido. En el proyecto se pueden distinguir tres bloques: la caracterización del ruido que afecta a grabaciones de discos de vinilo, el desarrollo de un algoritmo que realice la reducción de ruido correspondiente y el desarrollo de la aplicación web. En este documento se recogen los fundamentos de cada uno de los bloques, tratando de resumir las bases de su funcionamiento y de justificar cada una de las decisiones tomadas, como la tecnología empleada, el valor de algunos parámetros, la estructura del código o los pasos seguidos en cada algoritmo.

Sarney, agora em disco

Foto: Sarney e Monturil. Foto de: Secretaria da Imprensa e Divulgação.

Efeitos da remoção do disco e cartilagem articular no crescimento e microarquitetura óssea da mandíbula de ratos: análise por microtomografia

Alterações na articulação emporomandibular (ATM) comumente geram desequilíbrios musculares que estão associados à alterações no tecido ósseo. Esta articulação pode sofrer a influência de traumas, fatores congênitos ou desordens de crescimento. Estudos sobre alterações de crescimento do complexo maxilomandibular decorrentes de problemas da ATM são escassos. O objetivo deste trabalho foi avaliar por meio da microtomografia os efeitos da remoção do disco articular e a remoção conjugada do disco e cartilagem articular no crescimento e na microarquitetura óssea da mandíbula de ratos. Trinta ratos da raça Wistar com um mês de idade foram divididos em três grupos: CTR (controle operado); RD (remoção de disco articular) e RDC (remoção conjugada do disco e cartilagem articular). Apenas o lado direito foi operado; o lado esquerdo permaneceu intacto. Após dois meses de acompanhamento, os ratos foram sacrificados e as hemimandíbulas escaneadas em microtomógrafo A remoção do disco articular e a remoção conjugada do disco e cartilagem articular alteram o volume e microestrutura do osso trabecular da mandíbula de ratos jovens. Estas duas intervenções provocaram uma queda na qualidade de parâmetros da microestrutura do trabeculado do processo angular e diminuição do crescimento da hemimandíbula do lado operado.

Modelagem e controle de marcha de robôs bípedes com disco de inércia.

Esta tese trata de um robô bípede em caminhar dinâmico. Neste robô, que normalmente é um sistema sub-atuado, fazemos uso de um disco de inércia que funciona num certo sentido como um atuador adicional. Através deste disco, obtém-se mais liberdade para a elaboração de passos repetitivos e um aumento na robustez. Por outro lado, o sistema de controle dos passos deve controlar, além do passo propriamente dito, também a velocidade do disco, de modo que não sejam saturados os atuadores (motores elétricos). Apresentamos então um controlador capaz de realizar estas ações simultaneamente.

Drusen do disco óptico e tilted disc

Trabalho Final do Curso de Mestrado Integrado em Medicina, Faculdade de Medicina, Universidade de Lisboa, 2014

Memoria histórico-crítica sobre el Gran Disco de Teodosio, encontrado en Almendralejo /

Mode of access: Internet.

Capas de disco da gravadora Continental nos anos 1970: música popular e experimentalismo visual

Neste artigo, proponho discutir as inovações de algumas capas de discos de um conjunto de artistas experimentais da MPB nos anos 1970, lançados pela gravadora Continental, sediada em São Paulo. Esses álbuns, cujo design tentou traduzir para o campo visual os projetos estéticos de compositores e músicos, foram inspirados na contracultura, na tentativa de criar novas formas de expressão durante a ditadura militar. Discos de quatro artistas serão analisados: Walter Franco, Tom Zé, Secos & Molhados e Novos Baianos. A capa de disco será pensada não apenas como embalagem comercial, mas como elemento de mediação estética, de gosto e de consumo, dentro do campo midiático da canção.

Signposting for diagnosis of Autism Spectrum Disorder using the Diagnostic Interview for Social and Communication Disorders (DISCO)

Recent research has investigated the capability of the Diagnostic and Statistical Manual for Mental Disorders (DSM-5) descriptions to identify individuals who should receive a diagnosis of Autism Spectrum Disorder (ASD) using standardised diagnostic instruments. Building on previous research investigating behaviours essential for the diagnosis of DSM-5 ASD, the current study investigated the sensitivity and specificity of a set of 14 items derived from the Diagnostic Interview for Social and Communication Disorders (DISCO Signposting set) that have potential for signposting the diagnosis of autism according to both the new DSM-5 criteria for ASD and ICD-10 criteria for Childhood Autism. An algorithm threshold for the Signposting set was calculated in Sample 1 (n = 67), tested in an independent validation sample (Sample 2; n = 78), and applied across age and ability sub-groups in Sample 3 (n = 190). The algorithm had excellent predictive validity according to best estimate clinical diagnosis (Samples 1 and 2) and excellent agreement with established algorithms for both DSM-5 and ICD-10 (all samples). The signposting set has potential to inform our understanding of the profile of ASD in relation to other neurodevelopmental disorders and to form the basis of a Signposting Interview for use in clinical practice.