28 research outputs found

    Modelling of field-effect transistors based on 2D materials targeting high-frequency applications

    Get PDF
    New technologies are necessary for the unprecedented expansion of connectivity and communications in the modern technological society. The specific needs of wireless communication systems in 5G and beyond, as well as devices for the future deployment of Internet of Things has caused that the International Technology Roadmap for Semiconductors, which is the strategic planning document of the semiconductor industry, considered since 2011, graphene and related materials (GRMs) as promising candidates for the future of electronics. Graphene, a one-atom-thick of carbon, is a promising material for high-frequency applications due to its intrinsic superior carrier mobility and very high saturation velocity. These exceptional carrier transport properties suggest that GRM-based field-effect transistors could potentially outperform other technologies. This thesis presents a body of work on the modelling, performance prediction and simulation of GRM-based field-effect transistors and circuits. The main goal of this work is to provide models and tools to ease the following issues: (i) gaining technological control of single layer and bilayer graphene devices and, more generally, devices based on 2D materials, (ii) assessment of radio-frequency (RF) performance and microwave stability, (iii) benchmarking against other existing technologies, (iv) providing guidance for device and circuit design, (v) simulation of circuits formed by GRM-based transistors.Comment: Thesis, 164 pages, http://hdl.handle.net/10803/40531

    GigaHertz Symposium 2010

    Get PDF

    Compact Optical Frequency Standards for Future Applications Beyond the Laboratory

    Get PDF
    Atomic clocks provide one of the fundamental building blocks upon which modern telecommunications systems are constructed. Since the invention of the frequency comb in the early 2000s, laboratory frequency standards have quickly outpaced their compact counterparts. Compact clocks, however, have continued to leverage microwave transitions not yet exploring the advantages of an optical atomic clock. With the recent development of robust frequency combs compact optical clocks can now be realized. In this dissertation two atomic species are investigated for a compact atomic frequency standards. Both of these clocks are in different development stages but offer unique advantages. The optical rubidium atomic frequency standard relies on a two-photon transition in rubidium. This dissertation details the design necessary to achieve best clock stabilities to date leveraging this two-photon transition. Calculations and measurements of required environmental instabilities to reach stabilities of 1×10−151\times 10^{-15} at one day are included. The hardest environmental parameters to suppress are the self collisional shift and the ac-Stark shift. A new approach to reduce ac-Stark shift is discussed as well as a robust thermal design which achieved necessary temperature stabilities. Calcium provides a much narrower transition then the two-photon rubidium for which to build a clock. A calcium vapor cell could revolutionize experimentation with this species. This dissertation describes a first ever closed calcium vapor cell. I also describe a method for continuous operation of this vapor cell without replenishing calcium or cleaning the optical windows. The optical rubidium atomic frequency standard has shown fractional frequency instabilities of 4×10−13/τ(s)4\times 10^{-13}/\sqrt{\tau(s)} for τ\tau from 1 to 10,000 seconds, with potential to achieve instabilities of less then 1×10−131\times 10^{-13} at one second and less then 4×10−154\times 10^{-15} at one day. The calcium clock is still in vapor cell development stages, showing some promise for future fully realized calcium clock based on vapor cell technologies

    NASA Tech Briefs, January 1989

    Get PDF
    Topics include: Electronic Components & and Circuits. Electronic Systems, A Physical Sciences, Materials, Computer Programs, Mechanics, Machinery, Fabrication Technology, Mathematics and Information Sciences, and Life Sciences

    An aluminum optical clock setup and its evaluation using Ca+

    Get PDF
    This thesis reports about the progress of the aluminum ion clock that is set up at the German National Metrological Institute, Physikalisch-Technische Bundesanstalt (PTB) in Braunschweig. All known relevant systematic frequency shifts are discussed. The systematic shifts were measured on the co-trapped logic ion 40Ca+, which is advantageous due to its higher sensitivity to external fields compared to 27Al+. The observation of the clock transition of 27Al+ and an analysis of the detection error is described.DFG/DQ-mat/Project-ID 274200144 – SFB 1227/E

    Abstracts on Radio Direction Finding (1899 - 1995)

    Get PDF
    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

    GSI Scientific Report 2009 [GSI Report 2010-1]

    Get PDF
    Displacement design response spectrum is an essential component for the currently-developing displacement-based seismic design and assessment procedures. This paper proposes a new and simple method for constructing displacement design response spectra on soft soil sites. The method takes into account modifications of the seismic waves by the soil layers, giving due considerations to factors such as the level of bedrock shaking, material non-linearity, seismic impedance contrast at the interface between soil and bedrock, and plasticity of the soil layers. The model is particularly suited to applications in regions with a paucity of recorded strong ground motion data, from which empirical models cannot be reliably developed
    corecore