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Este trabalho tem por objetivo avaliar a capacidade de detecção e dimensionamento de descontinuidades internas em juntas soldadas dissimilares e cladeadas com a utilização da inspeção por ultrassom através da técnica de Phased Array. Este estudo se justifica pela possibilidade da aplicação desses materiais nas atividades de exploração de petróleo no campo offshore com a utilização de dutos rígidos de aço carbono com revestimento interno de Inconel. As juntas circunferenciais foram soldadas com material austenítico e foram realizados ensaios com juntas sem a realização do amanteigamento do bisel e com corpos de provas que receberam camadas de amanteigamento que tem a finalidade de aumentar a resistência à corrosão-fadiga da junta circunferencial. A tubulação soldada tinha como material de base um aço ferrítico API 5L X-52 com revestimento interno de Inconel 625. As descontinuidades foram inseridas nos passes de raiz fabricadas com o processo de soldagem TIG, nos passes de enchimento através do processo por eletrodos revestidos e na região da raiz através do processo de eletroerosão com a finalidade de simular uma falta de fusão na raiz. Para as inspeções foram adotados as varreduras setorial e linear com duas posições do cabeçote em relação à linha de centro da solda. Estas foram realizadas com o intuito de avaliar a capacidade de detecção e dimensionamento das descontinuidades através da utilização de ondas transversais com freqüência de 5 MHz e assim analisar os resultados encontrados para poder viabilizar a aplicação desta técnica como ferramenta de inspeção nestes equipamentos. Análises metalográficas serviram para realizar o dimensionamento real das descontinuidades e caracterizar a micrografia do metal de base, zona afetada pelo calor e metal de solda para poder correlacioná-los com os resultados encontrados nas inspeções por Phased Array. Assim com os resultados encontrados foi possível demonstrar a possibilidade de aplicação da técnica de Phased Array na inspeção das juntas dissimilares e cladeadas. / This work aims to evaluate the detection capability and sizing of internal discontinuities in dissimilar welded and claded joints with the use of Phased Array ultrasonic inspection technique. This study was performed due to the possibility of the application of those materials in the activities of exploration of petroleum in the offshore field with the use of rigid risers of carbon steel with internal covering of Inconel. The girths joints were welded with material austenitic and testing were accomplished with joints without the realization of the buttering of the bevel and with specimens that received layers of buttering that has the purpose of increasing the resistance to the corrosion-fatigue of the girth joint. The welded piping had as base material a ferritic steel API 5L X-52 with internal overlay of Inconel 625. The discontinuities were inserted in the root pass manufactured with the welding process TIG, in the filler pass through the process by covered electrodes and in the area of the root through the electric discharge machining process with the purpose of simulating a lack of fusion in the root. For the inspections the sectorial and linear sweepings were adopted with two positions of the transducer in relation to the line of center of the weld. This was performed with the intention of evaluating the detection capacity and sizing of discontinuities through the use of shear waves frequently of 5 MHz and like this to analyze the results found to make possible the application of this technique as inspection tool in these equipments. Metallographic analyses were to accomplish the real sizing of the discontinuities and to characterize the micrograph of the base metal, affected area for the heat and weld metal to correlate them with the results found in the inspections by Phased Array. Like this with the found results it was possible to demonstrate the possibility of application of Phased Array technique in the inspection of the dissimilar and claded joints.

Une technique de Contrôle Non Destructif (CND) a été développée, permettant la génération et la détection d’ondes de Lamb guidées le long de grandes plaques constituées de différents matériaux (métal, polymère ou composite renforcé par des fibres). Basée sur l’emploi de nombreux éléments étroitement couplés à la plaque, cette technique d’inspection diffère du Structural Health Monitoring (SHM) classique car tous les éléments émetteurs ou récepteurs sont regroupés dans une zone très localisée, définie par la surface active d’une sonde multiélément matricielle, et ne sont pas fixés de manière permanente et distribuée au sein, ou en surface, de la structure testée. De plus, le principe (connu) du déphasage entre éléments est appliqué à la sonde pour la génération et la réception d’un mode de Lamb pur dans (ou provenant) de multiples directions le long de la plaque. Les lois de retards appliquées à ces éléments, aussi bien lorsque la sonde fonctionne en mode émission qu’en mode réception, prennent en compte la nature dispersive de l’onde de Lamb. Enfin, un traitement de signal spécifique est appliqué pour compenser la dispersion subie par les ondes guidées au cours de leur propagation le long de la pièce testée. Un prototype expérimental et sa modélisation par éléments finis sont présentés, ainsi que les mesures et les résultats simulés de ses performances en termes de sélectivité modale et de directivité angulaire. Concernant les applications de CND, la construction d’images, représentatives de toutes les parties de la pièce testée qui diffractent le mode guidé (bord de pièce, défauts, trous, raidisseurs, etc.), a permis de démontrer le potentiel (et quelques limites) de cette technique vis-à-vis d’une inspection rapide de grandes structures, y compris de zones éloignées de la sonde ou encore de zones difficiles d’accès. / A technique of Non-Destructive Testing (NDT) was developed for the generation and detection of Lamb waves propagating along large plates made of different materials (metal, polymer or fibre-reinforced composite). Based on the use of many elements closely coupled to the plate, this inspection technique differs from the classic Structural Health Monitoring (SHM) because all the transmitters or receivers are grouped in a very localized area, defined by the active surface of a phased array matrix probe, and are not permanently attached and distributed within or on the surface of the test structure. In addition, the principle (known) of the phase shift between the elements is applied to the probe for generating and receiving a pure Lamb mode in (or from) multiple directions along the plate. The delay laws applied to these elements, in transmit mode or receive mode, take into account the dispersive nature of the Lamb wave. Finally, a specific signal processing is applied to compensate the dispersion suffered by the guided waves during their propagation along the test piece. An experimental prototype and its finite element modeling are presented, as well as measurements and simulation results of its performances in terms of modal selectivity and angular directivity. For NDT applications, the construction of images, representing all parts of the test piece, which diffract the guided mode (edges, defects, holes, stiffeners, etc.), has demonstrated the potential (and some limits) of this technique for a quick inspection of large structures, including areas remote from the probe or areas difficult to access.

<div>Integrated optical phased arrays (OPAs) have gained popularity for achieving beam steering with no moving parts and potential high speed and small beam divergence angle. These characteristics are crucial for applications like free-space communication and light detection and ranging (LiDAR), a key component in autonomous driving. Two main aspects that affect the performance of an integrated OPA are discussed: high power handling and large beam steering range.</div><div><br></div><div>High emission power from the OPA is desirable for long range detection applications. Silicon is broadly used in integrated OPA designs as it allows for structures with a more compact footprint. However, its power-handling capability is limited by the two-photon absorption of the material, resulting in higher loss and potential damage at high input power levels. In this work, high power delivery into free space is realized by using a silicon nitride (SiN) and silicon hybrid platform. SiN components are used to direct and split high input power into smaller portions and coupled into silicon components for a more compact emitter array.</div><div><br></div><div>In order to achieve a full 180-degree beam steering range with aliasing-free operation, the pitch of a periodic emitter array is required to be half of the operating wavelength or less. At such a small pitch, evanescent coupling between adjacent emitters causes strong crosstalk. We demonstrate the optical phased array based on uniform half-wavelength spaced grating emitter array. Two-dimensional beam confinement and a record-high aliasing-free beam steering field-of-view of 135 degrees from grating emitter are measured from a 32 channel SiN/Si hybrid OPA. Evanescent coupling between waveguides are suppressed by metamaterial-based <b>e</b>xtreme <b>ski</b>n-<b>d</b>epth (e-skid) waveguides. The e-skid waveguides utilize an alternating air-silicon multi-fin side cladding. The high index contrast of those sub-wavelength ridges provides strong anisotropy, which leads to faster decay of the evanescent wave for transverse electric (TE) input modes, thus limiting evanescent coupling between closely spaced waveguides.</div><div><br></div><div>Furthermore, we extend the concept of the half-wavelength-pitched emitter array to the design of a two-dimensional end-fire OPA. This OPA can potentially achieve 180-degree by 180-degree full-range beam steering with no grating lobes by having a half-wavelength emitter pitch in both dimensions. The design of a broadband 8 by 8 silicon photonics switch based on the half-wavelength-pitched emitter array with low path-dependent loss (PDL) is also discussed.</div>

The design of the RF over fiber signal transport system for the ALPACA receiver is described, with particular attention to the strict noise requirements as well as dynamic range considerations. Also discussed are analytical tools for analyzing dynamic range in the context of RFI-rich radio astronomy observational settings, including formulas for maximum interference to noise ratios and a simulation framework for predicting distortion levels. Phase and gain stability measurements of the signal transport system are presented, including the effects of the multi-strand armored fiber optic cable. The resulting system meets design requirements, with equivalent noise temperature below 900 K in 90° F ambient air, resulting in less than 1 K contribution to the system noise temperature. Typical gain is 31-37 dB, and gain differences between channels are stable within 0.25 dB in 90° F conditions. Phase drift between channels due to electronics remains below 1° at room temperature, and below 1.3° in a warm environment. The fiber optic cable is predicted to cause phase changes between channels of no more than 1.3° per °C. Typical spurious free dynamic range is 99 dB·Hz^(⅔), and distortion levels for normal RFI conditions at Arecibo are expected to be 28 dB below the system noise floor.

The design of the RF over fiber signal transport system for the ALPACA receiver is described, with particular attention to the strict noise requirements as well as dynamic range considerations. Also discussed are analytical tools for analyzing dynamic range in the context of RFI-rich radio astronomy observational settings, including formulas for maximum interference to noise ratios and a simulation framework for predicting distortion levels. Phase and gain stability measurements of the signal transport system are presented, including the effects of the multi-strand armored fiber optic cable. The resulting system meets design requirements, with equivalent noise temperature below 900 K in 90° F ambient air, resulting in less than 1 K contribution to the system noise temperature. Typical gain is 31-37 dB, and gain differences between channels are stable within 0.25 dB in 90° F conditions. Phase drift between channels due to electronics remains below 1° at room temperature, and below 1.3° in a warm environment. The fiber optic cable is predicted to cause phase changes between channels of no more than 1.3° per °C. Typical spurious free dynamic range is 99 dB·Hz^(⅔), and distortion levels for normal RFI conditions at Arecibo are expected to be 28 dB below the system noise floor.

Indiana University-Purdue University Indianapolis (IUPUI) / This thesis is an examination of one of the main technologies to be developed on the path to Space Solar Power (SSP): Wireless Power Transfer (WPT), specifically power beaming. While SSP has been the main motivation for this body of work, other applications of power beaming include ground-to-ground energy transfer, ground to low-flying satellite wireless power transfer, mother-daughter satellite configurations, and even ground-to-car or ground-to-flying-car power transfer. More broadly, Wireless Power Transfer falls under the category of radio and microwave signals; with that in mind, some of the topics contained within can even be applied to 5G or other RF applications. The main components of WPT are signal transmission, propagation, and reception. This thesis focuses on the transmission and propagation of wireless power signals, including beamforming with Phased Array Antennas (PAAs) and evaluations of transmission and propagation efficiency. Signals used to transmit power long distances must be extremely directive in order to deliver the power at an acceptable efficiency and to prevent excess power from interfering with other RF technology. Phased array antennas offer one method of increasing the directivity of a transmitted beam through off-axis cancellation from the multi-antenna source. Besides beamforming, another focus of this work is on the equations used to describe the efficiency and far field distance of transmitting antennas. Most previously used equations, including the Friis equation and the Goubau equation, are formed by examining singleton antennas, and do not account for the unique properties of antenna arrays. Updated equations and evaluation methods are presented both for the far field and the efficiency of phased array antennas. Experimental results corroborate the far field model and efficiency equation presented, and the implications of these results regarding space solar power and other applications are discussed. The results of this thesis are important to the applications of WPT previously mentioned, and can also be used as a starting point for further WPT and SSP research, especially when looking at the foundations of PAA technology.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第19712号 / 工博第4167号 / 新制||工||1643(附属図書館) / 32748 / 京都大学大学院工学研究科電気工学専攻 / (主査)教授 篠原 真毅, 教授 土居 伸二, 准教授 小嶋 浩嗣 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Presented herein is the design and construction process in the expansion of BYU's seven-element experimental platform to a nineteen-element platform for phased array feed experiments. The nineteen-element system was deployed at the National Radio Astronomy Observatory (NRAO) in Green Bank West Virginia for use on the Green Bank 20-Meter Telescope. Numerical simulations were performed to determine how sensitivity was affected by electronic beam steering and offset of the phased array feed (PAF) relative to the focal plane of the reflector. These simulated results were then compared to experimental data.

Recent developments in the field of phased array feeds for radio astronomical reflector antennas, have opened a new frontier for array signal processing for radio astronomy observations. The goal is to replace single horn feeds with a phased array feed, so as to enable astronomers to cover more sky area in less time. The development of digital backend signal processing systems has been a major area of concentration for the development of science-ready phased array feeds for radio astronomers. This thesis focuses on the development of analog down-converter receivers and an FPGA-based digital backend for real-time data processing and analysis support for phased array feeds. Experiments were conducted with new receiver boards and both single-polarization and dual-polarization phased array feeds at the Arecibo Observatory, Puerto Rico and at the 20-meter telescope at Green Bank, WV, and results were analyzed. The experiments were performed as a part of a feasibility study for phased array feeds. The new receiver boards were developed as an upgrade to the earlier connectorized receivers as the number of input channels increased from 19 to 38 and space constraints arose due to the large size of the earlier receivers. Each receiver card has four independent channels on it. The receiver cards were found to have lower cross-coupling between the channels in comparison to the earlier receivers. The development of a FPGA-based real time digital backend focused on a real-time spectrometer, beamformer and a correlator for all the 64-channels using a x64 ADC card and ROACH FPGA boards. The backend can plot results in real time and can stream and store the data on the computers for purpose of post-processing and data analysis. The design process uses libraries and blocks provided by the Center for Astronomy Signal Processing and Electronics Research (CASPER) community.