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  • 1
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    Phase-locked loops (1974)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The basic analysis and design procedures are described for the realization of analog phase-locked loops (APLL), hybrid phase-locked loops (HPLL), discrete phase-locked loops, and digital phase-locked loops (DPLL). Basic configurations are diagrammed, and performance curves are given. A discrete communications model is derived and developed. The use of the APLL as an optimum angle demodulator and the Kalman-Bucy approach to APLL design are discussed. The literature in the area of phase-locked loops is reviewed, and an extensive bibliography is given. Although the design of APLLs is fairly well documented, work on discrete, hybrid, and digital PLLs is scattered, and more will have to be done in the future to pinpoint the formal design of DPLLs.
    Keywords: COMMUNICATIONS
    Type: Communication Systems and Technology Conference; Apr 30, 1974 - May 01, 1974; Dallas, TX
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Theory for the effects of turbulence in a planetary atmosphere on radio occultation (1974)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Rytov's method is used to formulate the correlation functions for log-amplitude and phase fluctuations for both spherical and plane wave propagation in a turbulent medium whose correlation function for refractive index fluctuations is described by the product of a function of the average coordinate and a function of the difference coordinate. The results are applied to the study of radio occultation effects due to the atmosphere of Venus in the case of a flyby space probe. It is assumed that turbulence of isotropic and smoothly varying characteristics occurs in the Venusian atmosphere.
    Keywords: COMMUNICATIONS
    Type: Symposium on Electromagnetic Wave Theory; Jul 09, 1974 - Jul 12, 1974; London
    Format: text
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  • 3
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    The ATS-F/Nimbus-F tracking and orbit determination experiment (1974)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The experiment described was conducted to demonstrate a procedure for tracking a near-earth satellite via a geostationary satellite without the aid of multiple ground station tracking. Another objective of the experiment was connected with the utilization of the broad tracking coverage provided by the geostationary satellite to obtain an improved geopotential solution. Questions of overall experiment implementation are discussed along with details regarding ground equipment, the ATS-F transponder, and the Nimbus-F transponder. Aspects of measurement evaluation are also examined, taking into account basic measurements, measurement interpretation, and approaches for orbit computation.
    Keywords: COMMUNICATIONS
    Type: International Convention and Exposition; Mar 26, 1974 - Mar 29, 1974; New York, NY
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    A technique for correcting transmission errors in delta modulation channels (1974)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The delta modulator is a relatively new device which has found wide application in voice encoding. Two main difficulties in using this device for video encoding and processing is that it slope overloads and 'rings' and that channel errors produce a DC level shift. An algorithm is developed which is easily implemented and which significantly reduces 'picture streaks' due to the production of DC level shifts by channel errors. The algorithm can be made adaptive whereby the insertion rate of the pulse code modulation (PCM) codeword needed for correction can be adjusted depending on the strength of the channel noise. This yields a more efficient use of bandwidth. Further, the resulting signal can still be processed further using line-to-line correlation to remove the remaining 'streaks'.
    Keywords: COMMUNICATIONS
    Type: International Conference on Communications; Jun 17, 1974 - Jun 19, 1974; Minneapolis, MN
    Format: text
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  • 5
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    RFI Math Model programs for predicting intermodulation interference (1974)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Receivers operating on a space vehicle or an aircraft having many on-board transmitters are subject to intermodulation interference from mixing in the transmitting antenna systems, the external environment, or the receiver front-ends. This paper presents the techniques utilized in RFI Math Model computer programs that were developed to aid in the prevention of interference by predicting problem areas prior to occurrence. Frequencies and amplitudes of possible intermodulation products generated in the external environment are calculated and compared to receiver sensitivities. Intermodulation products generated in receivers are evaluated to determine the adequacy of preselector ejection.
    Keywords: COMMUNICATIONS
    Type: Electromagnetic Compatibility Symposium; Jul 16, 1974 - Jul 18, 1974; San Francisco, CA
    Format: text
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  • 6
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    Solar environment support for Skylab (1974)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Solar support for the ATM PIs (Apollo Telescope Mount Principle Investigators) and NASA was provided by NOAA's real-time data network through the NOAA-SOLAR facility in the ATM Science Support Room at Mission Control in Houston, Tex. Support was in the form of solar data - e.g., ground-based photographs of H-alpha (hydrogen-alpha), calcium, and magnetograms; voice/teletype reports of activity; analysis and forecasts; and assistance to the PIs and NASA as needed. This required establishing a communication system to a worldwide network of observatories, acquiring data transmission and dissemination equipment, and developing techniques to improve ATM related forecasts. This support began about one month before the first launch of the Skylab series and continued until splashdown of the last mission.
    Keywords: COMMUNICATIONS
    Type: AAS PAPER 74-170 , Annual Meeting; Aug 20, 1974 - Aug 22, 1974; Los Angeles, CA
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  • 7
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    Preliminary estimates of range measurements to a spacecraft by means of ground digitally controlled oscillators (1974)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Range measurements to the Pioneer 10 and Mariner 10 spacecraft were made, without the use of a ranging system per se, by using the Jet Propulsion Laboratory Deep Space Network's new digitally controlled oscillator (DCO) device. These measurements were accomplished by controlling the linear ramps of the transmitted carrier frequency with a recently installed DCO instrument at the Goldstone facility and analyzing the received linearly ramped Doppler data with a computer program. The accuracy of these range measurements is on the order of 1.5 km.
    Keywords: COMMUNICATIONS
    Type: AIAA PAPER 74-830 , Mechanics and Control of Flight Conference; Aug 05, 1974 - Aug 09, 1974; Anaheim, CA
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  • 8
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    Millimeter wavelength propagation studies (1974)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The investigations conducted for the Millimeter Wavelength Propagation Studies during the period December, 1966, to June 1974 are reported. These efforts included the preparation for the ATS-5 Millimeter Wavelength Propagation Experiment and the subsequent data acquisition and data analysis. The emphasis of the OSU participation in this experiment was placed on the determination of reliability improvement resulting from the use of space diversity on a millimeter wavelength earth-space communication link. Related measurements included the determination of the correlation between radiometric temperature and attenuation along the earth-space propagation path. Along with this experimental effort a theoretical model was developed for the prediction of attenuation statistics on single and spatially separated earth space propagation paths. A High Resolution Radar/Radiometer System and Low Resolution Radar System were developed and implemented for the study of intense rain cells in preparation for the ATS-6 Millimeter Wavelength Propagation Experiment.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-139366 , FR-2374-18 , ESL-2374-18
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 9
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    Optimal space communications techniques (1974)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Digital multiplication of two waveforms using delta modulation (DM) is discussed. It is shown that while conventional multiplication of two N bit words requires N2 complexity, multiplication using DM requires complexity which increases linearly with N. Bounds on the signal-to-quantization noise ratio (SNR) resulting from this multiplication are determined and compared with the SNR obtained using standard multiplication techniques. The phase locked loop (PLL) system, consisting of a phase detector, voltage controlled oscillator, and a linear loop filter, is discussed in terms of its design and system advantages. Areas requiring further research are identified.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-138606
    Format: application/pdf
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  • 10
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    Multi-frequency fine resolution imaging radar instrumentation and data acquisition (1974)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Development of a dual polarized L-band radar imaging system to be used in conjunction with the present dual polarized X-band radar is described. The technique used called for heterodyning the transmitted frequency from X-band to L-band and again heterodyning the received L-band signals back to X-band for amplification, detection, and recording.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-134212 , ERIM-198200-1-F
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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