4 research outputs found

    THE USE OF TUNED FRONT END OPTICAL RECEIVER AND PULSE POSITION MODULATION

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    The aim of this work is to investigate the use of tuned front-ends with OOK and PPM schemes, in addition to establish a theory for baseband tuned front end receivers. In this thesis, a background of baseband receivers, tuned receivers, and modulation schemes used in baseband optical communication is presented. Also, the noise theory of baseband receivers is reviewed which establishes a grounding for developing the theory relating to optical baseband tuned receivers. This work presents novel analytical expressions for tuned transimpedance, tuned components, noise integrals and equivalent input and output noise densities of two tuned front-end receivers employing bi-polar junction transistors and field effect transistors as the input. It also presents novel expressions for optimising the collector current for tuned receivers. The noise modelling developed in this work overcomes some limitations of the conventional noise modelling and allows tuned receivers to be optimised and analysed. This work also provides an in-depth investigation of optical baseband tuned receivers for on-off keying (OOK), Pulse position modulation (PPM), and Di-code pulse position modulation (Di-code PPM). This investigation aims to give quantitative predictions of the receiver performance for various types of receivers with different photodetectors (PIN photodetector and avalanche photodetector), different input transistors (bi-polar junction transistor BJT and field effect transistor FET), different pre-detection filters (1st order low pass filter and 3rd order Butterworth filter), different detection methods, and different tuned configurations (inductive shunt feedback front end tuned A and serial tuned front end tuned B). This investigation considers various optical links such as line of sight (LOS) optical link, non-line of sight (NLOS) link and optical fibre link. All simulations, modelling, and calculations (including: channel modelling, receiver modelling, noise modelling, pulse shape and inter-symbol interference simulations, and error probability and receiver calculations) are performed by using a computer program (PTC Mathcad prime 4, version: M010/2017) which is used to evaluate and analyse the performance of these optical links. As an outcome of this investigation, noise power in tuned receivers is significantly reduced for all examined configurations and under different conditions compared to non-tuned receivers. The overall receiver performance is improved by over 3dB in some cases. This investigation provides an overview and demonstration of cases where tuned receiver can be optimised for baseband transmission, offering a much better performance compared to non-tuned receivers. The performance improvement that tuned receivers offers can benefit a wide range of optical applications. This investigation also addresses some recommendations and suggestions for further work in some emerging applications such as underwater optical wireless communication (UOWC), visible light communication (VLC), and implantable medical devices (IMD). Keyword: Optical communications, Baseband receivers, Noise modelling, tuned front end, pulse position modulation (PPM)

    Integrated butt-coupled membrane laser for Indium Phosphide on Silicon platform

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    In this work we present the design and technology development for an integrated butt-coupled membrane laser in the IMOS (Indium Phosphide Membrane On Silicon) platform . Laser is expected to have a small footprint (less than 50 µm 2 ), 1 mA threshold current and a direct modulation frequency of 10 GHz

    Cumulative index to NASA Tech Briefs, 1986-1990, volumes 10-14

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    Tech Briefs are short announcements of new technology derived from the R&D activities of the National Aeronautics and Space Administration. These briefs emphasize information considered likely to be transferrable across industrial, regional, or disciplinary lines and are issued to encourage commercial application. This cumulative index of Tech Briefs contains abstracts and four indexes (subject, personal author, originating center, and Tech Brief number) and covers the period 1986 to 1990. The abstract section is organized by the following subject categories: electronic components and circuits, electronic systems, physical sciences, materials, computer programs, life sciences, mechanics, machinery, fabrication technology, and mathematics and information sciences

    Abstracts on Radio Direction Finding (1899 - 1995)

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    The files on this record represent the various databases that originally composed the CD-ROM issue of "Abstracts on Radio Direction Finding" database, which is now part of the Dudley Knox Library's Abstracts and Selected Full Text Documents on Radio Direction Finding (1899 - 1995) Collection. (See Calhoun record https://calhoun.nps.edu/handle/10945/57364 for further information on this collection and the bibliography). Due to issues of technological obsolescence preventing current and future audiences from accessing the bibliography, DKL exported and converted into the three files on this record the various databases contained in the CD-ROM. The contents of these files are: 1) RDFA_CompleteBibliography_xls.zip [RDFA_CompleteBibliography.xls: Metadata for the complete bibliography, in Excel 97-2003 Workbook format; RDFA_Glossary.xls: Glossary of terms, in Excel 97-2003 Workbookformat; RDFA_Biographies.xls: Biographies of leading figures, in Excel 97-2003 Workbook format]; 2) RDFA_CompleteBibliography_csv.zip [RDFA_CompleteBibliography.TXT: Metadata for the complete bibliography, in CSV format; RDFA_Glossary.TXT: Glossary of terms, in CSV format; RDFA_Biographies.TXT: Biographies of leading figures, in CSV format]; 3) RDFA_CompleteBibliography.pdf: A human readable display of the bibliographic data, as a means of double-checking any possible deviations due to conversion
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