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作者： Overmiller, Brock Morgan. University of Delaware.bElectrical and Computer Engineering.

学位级别：M.S.

The modern communications environment is becoming an increasingly crowded place, resulting in rapidly increasing demands on current technology. Military and civilian operations require the ability to locate and decode all communication signals in the environment. However, developments in RADAR RAdio Detection And Ranging) and communications technology are making it harder to effectively identify and maintain bandwidth usage for everyone. Millimeter waves---waves measured between one millimeter to one centimeter in wavelength---have only recently been explored as a new technology to replace the augment receiver architectures. These small wavelengths introduce many engineering challenges, such as: large atmospheric losses, poor sensitivity, and expensive electronic equipment. With growing developments in Microwave Photonics, low-noise RF amplifiers and high-speed modulators have demonstrated the ability to design RF communication links in the millimeter wave regime to counter such problems. However, despite these developments, toward a cost-effective, spatial division multiplexing SDM) receiver concept has not proved capable of being implemented as part of the next generation 5G wireless network infrastructure. To this end, we present a novel receiver architecture utilizing an optically addressed phased-array millimeter wave receiver based on optical-upconversion and signal recovery. This receiver is capable of geolocation and spatial multiplexing of multiple Tunable optically Paired Source TOPS) communication signals in its scene. Operating at 35 GHz, the receiver up-converts the received RF onto an optical sideband, which, to our advantage, contains all of the frequency, amplitude, and phase information of the received signals. Subsequent optical processing allows routing of the sideband to a free space detector port. Photomixing a coherent optical local oscillator LO) with the optical sideband performs heterodyne down-conversion to an Intermediate Frequency IF) whe

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Tradeoffs of the use of SiGe buffer layers in tandem GaAsP/Si solar cells

Tradeoffs of the use of SiGe buffer layers in tandem GaAsP/S...

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作者： Polyzoeva, Evelina Aleksandrova Massachusetts Institute of Technology

学位级别：博士

iii-V multi-junction solar cells currently have the highest reported theoretical and experimental energy conversion efficiency but their cost, mainly attributed to the use of expensive substrates, limits their widespread use for terrestrial applications. Successful integration of iii--V's on a Si substrate to enable a iii-V/Si tandem cell can lower the cost of energy by combining the high-efficiency of the iii--V materials with the low-cost and abundance of the Si substrate. A maximum theoretical efficiency of 44.8% from a tandem cell on Si can be achieved by using a GaAsP (Eg=1.7 eV) as the top cell. Out of several possible integration routes, the use of a linearly graded SiGe buffer as interfacial layer between the two cells potentially yields the highest quality for the epitaxial GaAsP layer, an essential requirement for realization of high-efficiency solar cells. In this thesis, the impact of the SiGe buffer layer on the optical and electrical characteristics of the bottom Si cell of a GaAsP/Si tandem solar cell was assessed via experimental work. The growth of a SiGe buffer layer was shown to increase the threading dislocation density and as a result the leakage current of the bottom Si cell by about 10x. In addition, the low-bandgap SiGe absorbs more than 80% of the light that is intended for the Si sub-cell, reducing the short-circuit current of the Si cell from 33 mA/cm² to only 6 mA/cm². By using a step-cell design, in which the SiGe was partially etched to allow more light to reach the bottom cell, the current was increased to 20 mA/cm². To quantify the merits of the studied approach as well as evaluate other approaches, we have carried out a theoretical study of absorbed irradiance in a Si single-junction cell, a bonded GaAsP/Si tandem cell, a GaAsP/SiGe/Si tandem cell as well as the step-cell design. The GaAsP/Si bonded tandem cell showed 24% relative improvement in light absorption over a single-junction Si cell. The addition of a SiGe graded buffer was

关键词： Electrical engineering and Computer Science

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Local control unit for ITER-India gyrotron test facility (IIGTF)

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FUSION engineering AND design 2016年 112卷 897-905页

作者： Rathod, Vipal Shah, Ronak Mandge, Deepak Parmar, Rajvi Rao, S. L. ITER India Inst Plasma Res Gandhinagar 382428 Gujarat India

Electron Cyclotron system on ITER, is one of the important RF ancillary systems based on high power Gyrotron RF sources, that is used for plasma heating and current drive applications. To operate a Gyrotron source, various auxiliary systems and services such as Super Conducting Magnet set, High Voltage Power Supplies, Auxiliary Power Supplies, Waveguide components, Cooling water system and a Local Control Unit (LCU) are required. The LCU plays a very crucial role for the safe and reliable operation of Gyrotron system. A dedicated full scale ITER prototype LCU is being developed for testing and commissioning of an ITER like Test Gyrotron at ITER-India Gyrotron Test facility (IIGTF). The main functions of LCU include Sequence Control, Local Interlock Protection and Real Time Data Acquisition. PLC based slow controller is used for implementing the Sequence Control & Slow Interlock functions. Critical Protection Interlocks are required to have a response time of <10 mu s and are implemented using custom built hardware and PXIe based fast controller. Also PXIe system is used for implementing Real Time Data Acquisition function that is required to have slow and fast acquisition with online visualization and off line analysis facility. A Signal Conditioning Unit (SCU) is used to interface and faithfully transmit the field signals to the remote control systems. Necessary controller hardware is procured and several pre-prototype developments have been taken up to establish the critical subsystems such as protection interlocks and SCU. Software applications for PLC and PXIe systems are being developed using LabVIEW (TM) and CODAC Core System platforms. Here, we provide an overview of the prototype LCU for IIGTF, which includes the architecture, implementation topology, prototype test results along with the current status. (C) 2016 Elsevier B.V. All rights reserved.

关键词： ITER ECH&CD Gyrotron Data acquisition and control optical link

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developments in fiber-positioning technology for the WEAVE instrument at the William Herschel Telescope 6

Developments in fiber-positioning technology for the WEAVE i...

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Ground-Based and Airborne Instrumentation for Astronomy VI

作者： Schallig, Ellen Lewis, Ian J. Gilbert, James Dalton, Gavin Brock, Matthew Abrams, Don Carlos Middleton, Kevin Aguerri, J. Alfonso L. Bonifacio, Piercarlo Carrasco, Esperanza Trager, Scott C. Vallenari, Antonella Dept. of Physics University of Oxford Keble Road OX1 3RH United Kingdom RSAA Mount Stromlo Observatory Cotter Road Weston CreekACT2611 Australia RAL Space Science and Technology Facilities Council Rutherford Appleton Laboratory Harwell Oxford Didcot OxfordshireOX11 OQX United Kingdom Isaac Newton Group Santa Cruz de La Palma38700 Spain Instituto de Astrofisica de Canarias La Laguna Tenerife38200 Spain GEPI Observatiore de Paris Place Jules Janssen Meudon92195 France Mexico Kapteyn Instituut Rijksuniversiteit Groningen Postbus 800 GroningenNL-9700 AV Netherlands Osservatorio Astronomico di Padova INAF Vicolo Osservatorio 5 Padova35122 Italy

ISBN: (数字)9781510601963

ISBN: (纸本)9781510601956

WEAVE is the next-generation wide-field optical spectroscopy facility for the William Herschel Telescope (WHT) on La Palma in the Canary Islands, Spain. It is a multi-object "pick-and-place" fibre-fed spectrograph with a 1000 fibre multiplex behind a new dedicated 2° prime focus corrector. The WEAVE positioner concept uses two robots working in tandem in order to reconfigure a fully populated field within the expected 1 hour dwell-time for the instrument (a good match between the required exposure times and the limit of validity for a given configuration due to the effects of differential refraction). In this paper we describe some of the final design decisions arising from the prototyping phase of the instrument design and provide an update on the current manufacturing status of the fibre positioner system. © 2016 SPIE.

关键词： Fibers

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Proceedings of SPIE - The International Society for optical engineering

Proceedings of SPIE - The International Society for Optical ...

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Vertical External Cavity Surface Emitting Lasers (VECSELs) VI

ISBN: (纸本)9781628419696

The proceedings contain 31 papers. The topics discussed include: generation of new spatial and temporal coherent light states using iii-V semiconductor laser technology: VORTEX, continuum, dual frequency for THz;terahertz quantum cascade VECSEL;broadly tunable DBR-free semiconductor disk lasers;resonant measurements of nonlinear lensing in a VECSEL gain sample;ultrafast characterization of semiconductor gain and absorber devices for mode-locked VECSELs;reection z-scan measurements of the non-linear lens in VECSEL gain structures;self-mode-locked vertical-external-cavity surface-emitting laser;a 1.5-W frequency-doubled semiconductor disk laser tunable over 40 nm at around 745 nm;advances in optically pumped semiconductor lasers for blue emission under frequency doubling;over 10 watt, collinear blue and green vertical external cavity surface emitting laser;gain chip design, power scaling and intra cavity frequency doubling with LBO of optically pumped red-emitting AlGaInP-VECSELs;influence of kinetic hole filling on the stability of mode-locked semiconductor disk lasers;advances in commercial, mode-locked vertical external cavity surface emitting lasers;and vertical external cavity surface emitting lasers for sodium guidestar applications and improvement of current guidestar systems.

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design, developments, and results from the NIST additive manufacturing metrology testbed (AMMT) 27

Design, developments, and results from the NIST additive man...

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27th Annual International Solid Freeform Fabrication Symposium - An Additive Manufacturing Conference, SFF 2016

作者： Lane, B. Mekhontsev, S. Grantham, S. Vlasea, M.L. Whiting, J. Yeung, H. Fox, J. Zarobila, C. Neira, J. McGlauflin, M. Hanssen, L. Moylan, S. Donmez, A. Rice, J. Engineering Laboratory National Institute of Standards and Technology GaithersburgMD20899 United States Physical Measurement Laboratory National Institute of Standards and Technology GaithersburgMD20899 United States Mechanical and Mechatronics Engineering University of Waterloo WaterlooONN2L 3GI Canada

The National Institute of Standards and Technology (NIST) is developing a facility titled the Additive Manufacturing Metrology Testbed that will enable advanced research into monitoring, controls, process development, and temperature measurement for laser powder bed fusion additive manufacturing and similar processes. This system provides an open control architecture as well as a plethora of sensor systems and calibration sources that are primarily radiance-based and aligned co-axially with the laser beam and focused on the laser interaction zone. This paper briefly reviews the system requirements, and details the current progress of the facility design and construction. Mechanical, optical, and control systems designs are detailed with select highlights that may be relevant to additive manufacturing researchers and system developers. Recent experimental results from the prototype laser control and in-situ monitoring system are also highlighted. © 2016 The Department of Energy’s Kansas City National Security Campus is operated and managed by Honeywell Federal Manufacturing Technologies, LLC under contract number DE-NA0002839.

关键词： 3D printers

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Novel hybrid iii:V concentrator photovoltaic-thermoelectric receiver designs

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AIP Conference Proceedings 2017年第1期1881卷

作者： Tracy K. N. Sweet Matthew H. Rolley Martin J. Prest Gao Min Cardiff School of Engineering Cardiff University Queen’s Buildings The Parade Cardiff. CF24 3AA. UK

This paper presents the design, manufacture and electrical characterization of novel hybrid iii:V Concentrator Photovoltaic-Thermoelectric receivers. Addition of an encapsulating and spectral homogenizing single active surface secondary optic lens increased the solar cell electrical power output from 7.66mW (ALPHA no cooling) to 18.20mW (KAPPA with TE cooling). The effective optical concentration of the optics, based on short circuit current, was x2.4. A linear irradiance vs maximum power receiver output relationship was observed (R2=0.9978), confirming good optical alignment during manufacture and likewise internal current matching of the series-connected triple-junction cell. An in-depth COMSOL model for simulated evaluation of the synergistic thermally-dependent parameters inherent to hybrid devices was built and experimentally validated.

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Scanning the Issue

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IETE JOURNAL OF RESEARCH 2016年第2期62卷 127-128页

作者： Koul, Shiban K.

The Volume 62, May-June 2016 issue of IETE Journal of Research contains articles on research and developments taking place in the broad areas of Electrical engineering. The paper 'On feasibility conditions for linear interference alignment over cognitive interference channel: A DoF analysis with diversity tradeoff' presents analytical studies related to multiuser opportunistic interference alignment (OIA) scheme in a multiple-antenna cognitive radio network. The paper 'Cost-effective optimal allocation and sizing of active power filters using a new fuzzy-MABICA method', deals with the active power filters in distribution systems. The next paper titled 'Reversible comparator design using quantum dot-cellular automata', presents the design of a reversible building block for a 1-bit comparator and gives its implementation in quantum dot cellular automata (QCA). The next paper on 'Gate Tunneling current Model for NanoscaleMOSFETS with Varying Surface Potential' deals with development of a simple first-order analytical model for evaluating gate tunnelling current through thin dielectrics in Nanoscale MOSFETs. In the paper on 'A physics-based model of double-gate tunnel FET for circuit simulation', an accurate device physics-based model for double-gate tunnel FET (TFET) is developed and integrated with Cadence circuit simulator.

关键词： Comparators (optical)

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Tolerancing an optical freeform surface: an optical fabricator's perspective 16

Tolerancing an optical freeform surface: an optical fabricat...

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Conference on current developments in Lens design and optical engineering XVI

作者： Nelson, Jessica DeGroote Medicus, Kate Frisch, Gregory Optimax Syst Inc Ontario NY 14519 USA

ISBN: (纸本)9781628417449

Freeform optical shapes or optical surfaces that arc designed with non-symmetric features arc gaining popularity with lens designers and optical system integrators. Tolerances on a freeform optical design influence the optical fabrication process. Case studies and soft tolerance limits for easier fabrication will be discussed. This paper will also give a high level overview of a freeform optical fabrication process that includes generation. high speed VIBE polishing, sub-aperture figure correction and testing of freeform surfaces.

关键词： Freeform optics manufacturing tolerance fabrication asphere

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Analysis of three-element zoom systems for laser beam expanders with tunable-focus lenses 16

Analysis of three-element zoom systems for laser beam expand...

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Conference on current developments in Lens design and optical engineering XVI

作者： Kulmon, Pavel Miks, Antonin Novak, Pavel Novak, Jiri Czech Tech Univ Fac Civil Engn Dept Phys Prague 16629 Czech Republic

ISBN: (纸本)9781628417449

Our work is focused on the problem of a theoretical analysis of imaging properties and an initial optical design of a three-element zoom optical system for laser beam expanders using lenses with a tunable focal length. Equations that enable to calculate basic paraxial properties and parameters of such optical systems are derived Finally, the derived equations are applied on an example of calculation of parameters of the three-element zoom system for the laser beam expander.

关键词： geometric optical design first-order optics zoom lenses laser beam expander Gaussian beam tunable-focus lenses

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