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Proceedings of the IEEE

Issue 7 • Date July 1991

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Displaying Results 1 - 25 of 25
  • Walter R.G. Baker and the advent of commercial television in 1941 [Scanning the Past]

    Publication Year: 1991, Page(s):0185 - 0186
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (134 KB)

    The role of Walter R.G. Baker, who worked for the General Electric Company and served as chairman of the National Television System Committee (NTSC) and who played a major role in the resolution of conflicting views in the early development of the television industry is discussed. The NTSC standards that have lasted to the 1990s included a 525 line picture with interlaced scanning at 30 frames per... View full abstract»

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  • Time, frequency and space geodesy: impact on the study of climate and global change

    Publication Year: 1991, Page(s):1063 - 1069
    Cited by:  Papers (8)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (788 KB)

    The authors discuss the development of space geodetic systems-important tools in an attempt to understand the evolution of the atmosphere and oceans-particularly as they pertain to the problem of global warming. The science of time and frequency metrology has made possible the development of space geodetic systems that are being applied to the high accuracy tracking of new space-based instruments.... View full abstract»

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  • Time synchronization using laser techniques

    Publication Year: 1991, Page(s):1001 - 1008
    Cited by:  Papers (2)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (544 KB)

    The author explains why light pulses are an important tool for time coordination and discuss the activities and the problems in this field. The author reviews the scientific and technical problems propelling the search for very accurate time comparison. A laser comparison method is discussed which is very simple in principle. This is followed by a discussion of the first experiments performed in F... View full abstract»

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  • Characterization of frequency stability: frequency-domain estimation of stability measures

    Publication Year: 1991, Page(s):961 - 972
    Cited by:  Papers (21)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (948 KB)

    The author focuses on the frequency domain approach, which provides a complete characterization of frequency. The standard characterization of frequency stability in the frequency domain is the spectral density function (SDF). The author describes SDFs that model sampled frequency stability data and that are related to the SDFs of the standard characterization. On the basis of standard techniques ... View full abstract»

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  • Millisecond pulsars: nature's most stable clocks

    Publication Year: 1991, Page(s):1054 - 1062
    Cited by:  Papers (36)  |  Patents (3)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (768 KB)

    The author describes the role pulsars might play in time and frequency technology. Millisecond pulsars are rapidly rotating neutron stars: some 20 km in diameter, 1.4 times as massive as the Sun, and spinning as fast as several thousand radians per second. Radio noise generated in a pulsar's magnetosphere by a highly beamed process is detectable over interstellar distances, as a periodic sequence ... View full abstract»

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  • GPS time transfer

    Publication Year: 1991, Page(s):991 - 1000
    Cited by:  Papers (80)  |  Patents (11)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (800 KB)

    The authors describe the use of GPS (Global Positioning System) for time coordination. When GPS first became available, it provided a quantum leap in time coordination with little or no effort on the part of the user. However, workers realized that with more sophisticated analysis techniques even greater accuracy could be wrung from GPS. The authors describe the level of time coordination these mo... View full abstract»

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  • Characterization of frequency stability in precision frequency sources

    Publication Year: 1991, Page(s):952 - 960
    Cited by:  Papers (108)  |  Patents (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (724 KB)

    The authors present a short review of the progress that has occurred during years 1955-91 in both the theoretical and practical characterization of frequency stability of precision frequency sources. The emphasis is on the evolution of ideas and concepts for the characterization of random noise processes in such standards in the time domain and the Fourier frequency domain, rather than a rigorous ... View full abstract»

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  • Applications of highly stable oscillators to scientific measurements

    Publication Year: 1991, Page(s):1040 - 1053
    Cited by:  Papers (7)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (948 KB)

    The author describes several scientific experiments requiring highly stable oscillators. It is clear from this analysis that technology has advanced to the point where concepts of relativity theory can be tested in a number of ways. He shows sigma versus tau plots for stored ion devices, for atomic hydrogen masers, and for a binary pulsar. In the discussion of experimental techniques, the H maser ... View full abstract»

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  • Astronomical time

    Publication Year: 1991, Page(s):915 - 920
    Cited by:  Papers (8)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (472 KB)

    Astronomical time serves as the basis for civil time and is required to describe the orientation of the Earth with respect to an inertial reference frame. The definitions of astronomical time scales are reviewed as well as observational methods. The causes of the variations in the Earth's rotation are explained and a brief overview of international efforts to maintain astronomical time scales is p... View full abstract»

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  • Two-way time transfer via communication satellites

    Publication Year: 1991, Page(s):983 - 990
    Cited by:  Papers (86)  |  Patents (10)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (772 KB)

    The history of two-way satellite time transfer is provided and developments in satellite communications technology conducive to this time transfer technique are briefly reviewed. The difference between one-way and two-way satellite time transfer is explained, and the advantages and disadvantages of the two-way method are pointed out. The theory of the two-way technique using geostationary communic... View full abstract»

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  • An introduction to frequency standards

    Publication Year: 1991, Page(s):927 - 935
    Cited by:  Papers (16)  |  Patents (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (728 KB)

    Quartz oscillators and rubidium, cesium, and hydrogen atomic frequency standards are described in terms of the physics of operation. Sources of frequency instability and inaccuracy are given. The author's intention is to provide a basis for characterization of the more practical aspects of commercially available frequency standards, and to present a comparison of such standards which may be useful... View full abstract»

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  • Laser-cooled neutral atom frequency standards

    Publication Year: 1991, Page(s):943 - 951
    Cited by:  Papers (21)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (840 KB)

    The authors review the prospects for a frequency standard based on what is called the atomic fountain. Atomic fountain frequency standards have better signal-to-noise ratios than ion standards, but suffer from larger systematic effects. An analysis of a Cs microwave fountain predicts potential stability and accuracy improvements of a factor of 100 over other laboratory standards, with an ultimate ... View full abstract»

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  • Comments, with reply, on `Matrix formulation for Dolph-Chebyshev beamforming' by A. Zielinski

    Publication Year: 1991, Page(s):1083 - 1084
    Cited by:  Papers (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (124 KB)

    In the above-titled letter by A. Zielinski (see ibid., vol.74, p.1799-1800, Dec. 1986), two linear sampling intervals are proposed for the matrix determination of Dolph-Chebyshev weights, for the case of a linear array consisting of an even number of elements. However, it appears that the use of either interval results identically in a rank-deficient coefficient matrix, such that a solution is not... View full abstract»

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  • Comments, with reply, on `Performance of coherent optical receivers' by J.R. Barry and E.A. Lee

    Publication Year: 1991, Page(s):1080 - 1082
    Cited by:  Papers (2)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (200 KB)

    The commenter shows how nonzero extinction ratios affect the performance of an otherwise ideal on-off keyed (OOK) communication system. In their reply, J.R. Barry and E.A. Lee point out that by using these results, experimenters will be able to state accurately what fraction of their sensitivity deviation from the ideal quantum limit is due to the nonzero extinction ratio. The ideal ten-photon qua... View full abstract»

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  • Synchronization and relativity

    Publication Year: 1991, Page(s):1029 - 1039
    Cited by:  Papers (6)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (1008 KB)

    The author gives an introduction to the concepts of both special and general relativity-particularly as they apply to time coordination. The use of concepts and formulas of the special and of the general theory of relativity has become a necessity in electronic systems that use high precision timing, especially space systems. The principles involved are reviewed with emphasis on practical applicat... View full abstract»

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  • Time generation and distribution

    Publication Year: 1991, Page(s):906 - 914
    Cited by:  Papers (4)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (920 KB)

    The authors present a broad overview of time and frequency technology, particularly those trends relating to the generation and distribution of time and frequency signals. The authors provide a general look at these trends. They refer the reader to other papers, particularly to those in this issue, for greater detail. The topics considered are: background, including accuracy and stability, frequen... View full abstract»

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  • Time and frequency in fundamental metrology

    Publication Year: 1991, Page(s):1070 - 1076
    Cited by:  Papers (2)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (616 KB)

    The author shows that because time and frequency are the most accurately measured physical quantities, it is desirable to tie other physical quantities to time and frequency measurements. A review of the progress that has been made in this direction along with speculation on possibilities for the future are given. The role of time and frequency in a wide range of measurements is discussed, particu... View full abstract»

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  • Uses of precise time and frequency in power systems

    Publication Year: 1991, Page(s):1009 - 1018
    Cited by:  Papers (22)  |  Patents (2)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (884 KB)

    The author discusses the need for accurate time coordination in the generation and distribution of electric power. He points out that the efficiency of present electric power systems can be increased with the addition of time and frequency technology, and that the same technology is an important ingredient in new electric power systems. Knowledge of the location of a short circuit fault can speed ... View full abstract»

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  • Satellite broadcasting of time and frequency signals

    Publication Year: 1991, Page(s):973 - 982
    Cited by:  Papers (9)  |  Patents (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (820 KB)

    The authors discuss the advantages of broadcasting time from a satellite over the more traditional ground based methods such as short wave and low frequency standard time and frequency broadcasts. The authors describe several one way satellite time services currently operational and discuss, in particular, a broadcast service using the Indian domestic satellite INSAT. The signal format, transmitti... View full abstract»

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  • The past, present, and future of atomic time and frequency

    Publication Year: 1991, Page(s):921 - 926
    Cited by:  Papers (3)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (572 KB)

    The early history of atomic time and frequency standards is reviewed. The most accurate and stable present standards are described. Prospective future improvements, particularly with trapped ions and atoms, are discussed. A historical perspective on this topic is provided View full abstract»

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  • Atomic ion frequency standards

    Publication Year: 1991, Page(s):936 - 942
    Cited by:  Papers (11)  |  Patents (4)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (596 KB)

    The history and status of trapped-ion frequency standards are reviewed. In a trapped-ion frequency standard, the frequency of an oscillator is servoed to a resonance which corresponds to a transition between two energy levels of an atomic ion. The ions are suspended in space by a combination of electric and magnetic fields. In a conventional rubidium cell, the atoms are surrounded by a buffer gas ... View full abstract»

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  • Comments, with reply, on `Ada technology: current status and cost impact' by P. Bhansali

    Publication Year: 1991, Page(s):1082 - 1083
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (160 KB)

    The commenter argues that, in the above-titled paper by P.V. Bhansali (see ibid., vol.79, p.22-29, 1991): (a) data reported to be supported by a footnoted reference are not in the referenced article; (b) data in a referenced article that are at variance with the conclusions reached in the paper were not included; and (c) when these data are included, the conclusions reached concerning Ada producti... View full abstract»

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  • Time and frequency information in telecommunications systems standardized by Federal Standard 1002A

    Publication Year: 1991, Page(s):1077 - 1079
    Cited by:  Papers (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (304 KB)

    The Federal Standard entitled Time and Frequency Information in Telecommunication Systems establishes the requirements for telecommunications facilities and systems of the Federal government for obtaining Coordinated Universal Time (UTC) coordinated time and frequency reference information based on national time scales maintained by the National Institute of Standards and Technology (NIST) and the... View full abstract»

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  • Synchronization in digital communications networks

    Publication Year: 1991, Page(s):1019 - 1028
    Cited by:  Papers (22)  |  Patents (14)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (984 KB)

    The general aspects of timing and synchronization in digital communications networks are reviewed. The properties of the links and nodes carrying and switching time-multiplexed digital signals determine the throughput and performance of a network. The continuity and integrity conditions for the digital information flow, where timing faults cause errors and loss of information, determine the requir... View full abstract»

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  • The BIPM and the accurate measurement of time

    Publication Year: 1991, Page(s):894 - 905
    Cited by:  Papers (12)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (888 KB)

    The role of the Bureau International des Poids et Mesures (BIPM) in assuring the uniformity and reliability of the world's measurement system is described. A brief discussion follows on the meaning of the term accurate measurement. The development of atomic time scales is outlined with particular reference to the Bureau International de l'Heure and the origins of International Atomic Time (TAI) an... View full abstract»

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