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  • COMMUNICATIONS AND RADAR
  • 1980-1984
  • 1975-1979  (166)
  • 1950-1954
  • 1976  (166)
  • 1
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    The Communications Technology Satellite /CTS/ Program (1976)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: The purposes of the joint Canadian-U.S. Communications Technology Satellite (CTS) Program are (1) to conduct satellite communication systems experiments using the 12- and 14-GHz bands and low-cost transportable ground terminals, (2) to develop and flight test a power amplifier tube having a greater than 50% efficiency with a saturated power output of 200 W at 12 GHz, (3) to develop and flight test a lightweight extendible solar array with an initial power output greater than 1 kW, and (4) to develop and flight test a 3-axis stabilization system to maintain accurate antenna boresight positioning on a spacecraft with flexible appendages. Brief descriptions of these experiments and of the ground facilities are provided.
    Keywords: COMMUNICATIONS AND RADAR
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  • 2
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    Television applications of interline-transfer CCD arrays (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The design features and characteristics of interline transfer (ILT) CCD arrays with 190 x 244 and 380 x 488 image elements are reviewed, with emphasis on optional operating modes and system application considerations. It was shown that the observed horizontal resolution for a TV system using an ILT image sensor can approach the aperture response limit determined by photosensor site width, resulting in enhanced resolution for moving images. Preferred camera configurations and read out clocking modes for maximum resolution and low light sensitivity are discussed, including a very low light level intensifier CCD concept. Several camera designs utilizing ILT-CCD arrays are described. These cameras demonstrate feasibility in applications where small size, low-power/low-voltage operation, high sensitivity and extreme ruggedness are either desired or mandatory system requirements.
    Keywords: COMMUNICATIONS AND RADAR
    Type: JPL Conf. on Charge-Coupled Device Technol. and Appls.; p 152-156
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  • 3
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    Television cameras employing solid-state imaging sensors for manned spacecraft applications (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The Space Shuttle television system incorporates a versatile complement of TV equipment which allows the positioning, quantity, and performance capabilities of the multiple TV cameras to vary as dictated by the particular mission. However, current TV camera technology employing glass enclosed, vacuum processed image sensors results in a bulky device that restricts its location and versatility. Problems and potential solutions that can be achieved through the employment of solid-state image sensors for both monochrome and color applications are discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: JPL Conf. on Charge-Coupled Device Technol. and Appls.; p 126-128
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  • 4
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    Command detector SNR estimator and lock status monitor circuitry (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A breadboard of the command detector signal-to-noise-ratio estimator and lock status monitor was built on a wire-wrap card. The breadboard was integrated with the standard command detector, and its performance was measured. The design, design constraints, and construction of the breadboard are described. The performance is shown to agree with the theoretical model.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 42-51
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  • 5
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    The scattering of obliquely incident plane waves from a corrugated conducting surface (1976)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: A physical optics solution is presented for the scattering of plane waves from a perfectly conducting corrugated surface in the case of waves incident from an arbitrary direction and for an observer far from the surface. This solution is used to compute the radar cross section of the surface in the case of backscatter from irregular (i.e., stochastic) corrugations. An interesting feature of the solution is the occurrence of singularities in the scattered fields. These singularities appear to be a manifestation of focusing by the surface at its 'stationary' points. Whether or not the singularities occur in the solution depends on the manner in which one restricts the analysis to the far-field.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation; AP-24; Nov. 197
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  • 6
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    Radio frequency boresight analysis of the low cost 64-meter antenna (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Configurations (two) of the reflector-only assemblies, using different width backup cones, are analyzed for RF boresight direction changes and wind distortions. The wider backup cone is best for minimum weight; however, there is an optimum weight which minimizes the RF boresight errors for a wind load that produces the maximum pitching moment of both configurations.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 128-135
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  • 7
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    Magnitude of 64-m elevation axis movements due to alidade temperature changes (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: In projected very-long baseline interferometry (VLBI) work a reference point for 64-m antennas is the intersection of the elevation and azimuth axes. A minimum-level effort at DSS 14 to determine the magnitude of the effect of diurnal changes in the temperature of the alidade legs on the height of the elevation axis is described. The thermal expansion between the lowest recorded temperature -3 C (27 F) and the highest, 36 C (97 F), over the period covered was 8.9 mm (0.35 in.).
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 41-44
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  • 8
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    Remote intensity fluctuation measurements with a laser Doppler radar (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: A coaxial focused CW scanning laser Doppler velocimeter (SLDV) radar equipment applying heterodyne detection at 10.6 microns can measure intensity fluctuations under field conditions. The set includes a 20 W CO2 laser, a coaxial Cassegrainian telescope, standard heterodyne equipment, and a SAW spectrum analyzer with 100 kHz signal resolution. Operation of the equipment and techniques for taking remote measurements are described briefly. Applications to remote measurements of transverse component of wind speed, as a complement to the traditional Doppler method of determining axial velocity, are under study. SLDV equipment has been used in detection, tracking, and measurements of atmospheric turbulence associated with aircraft wing-tip vortices or with dust devils, and in measurement of general atmospheric wind profiles.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Applied Optics; 15; Sept
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  • 9
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    New sidelobe envelopes for small aperture earth stations (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The advent of domestic satellite systems and technological improvements in both space and ground equipment makes the use of small aperture earth stations economically feasible and attractive for broadcast satellite applications. With increasing use of the orbit spectrum, there is some concern that broadcast satellite systems may not be able to obtain satisfactory allocations of this orbit-spectrum resource because of interference considerations. Specifically, interference calculations based on the present envelope result in comparatively large orbit spacings for broadcast satellites. Theoretical and experimental investigations of simple sidelobe suppression techniques, plus an analysis of experimental data on small aperture antennas, indicate that much better sidelobe performance can be obtained with a very small cost or performance penalty.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Broadcasting; BC-22; June 197
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  • 10
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    The input admittance of the rectangular cavity-backed slot antenna (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The input admittance of the rectangular cavity-backed slot antenna is investigated. The slot is assumed narrow so that the voltage distribution in its aperture is sinusoidal. Equations which represent the input admittance of this slot, backed by a rectangular cavity in which a single propagating wave is assumed to exist, are given. Calculations based on these representations are compared to available measured data. As the depth of the cavity increased the resonant frequency decreased and the bandwidth became narrower. Input admittance curves as a function of electrical slot length are also presented for several size cavities.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation; AP-24; May 1976
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  • 11
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    Power conservation for reflector antennas with truncated feed patterns (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Reflector-antenna calculations using idealised truncated feed patterns can lead to incorrect values of total secondary radiated power. It is demonstrated that this discrepancy is due to the presence of higher-order spherical modes incident on the reflector. When a proper spherical-wave expansion of the incident field is used, in conjunction with the physical-optics technique, to determine the scattered field, the total power of the scattered field will equal the power radiated by the feed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Electronics Letters; 12; Mar. 18
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  • 12
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    Satellite communications at the Goddard Space Flight Center (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Starting with the 1960 Delta launch of the first Echo satellite, NASA's Goddard Space Flight Center (GSFC) became one of the pioneers in satellite communications. Attention is given to the project Syncom, the Applications Technology Satellite (ATS) program, the ATS-6 project, and current GSFC efforts. After the decision announced in January of 1973 that NASA would phase out of communications satellite programs, the communications effort at GSFC concentrates on the operation of ATS spacecraft in orbit, experiments in the 12- to 14 GHz frequency band, and advanced communications research.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Signal; 30; Mar. 197
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  • 13
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    Real-time video compression algorithm for Hadamard transform processing (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: A real-time digital video processor using Hadamard transform techniques to reduce video bandwidth is described. The processor can be programmed with different parameters to investigate various algorithms for bandwidth compression. The processor is also adaptive in that it can select different parameter sets to tradeoff spatial resolution for temporal resolution in the regions of the picture that are moving. Algorithms used in programming the system are described along with results achieved at various levels of compression. The algorithms relate to spatial compression, temporal compression, and the adaptive selection of parameter sets.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Electromagnetic Compatibility; EMC-18; Feb. 197
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  • 14
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    Frequencies above 10 GHz (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The paper discusses some of the problems associated with extending the frequencies used by satellite communication services above 10 GHz. The principal propagation limitation above 10 GHz occurs when precipitation intercepts the earth-space propagation path and causes attenuation and depolarization of the transmitted signal. World attenuation statistics at 12 GHz for earth-space paths are discussed, revealing the effect of climate on attenuation properties. Space diversity is discussed as an effective means of overcoming precipitation-caused attenuation problems.
    Keywords: COMMUNICATIONS AND RADAR
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  • 15
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    Analysis of the radiation patterns of reflector antennas (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The development and application of a numerical technique for rapid calculation of the far-field radiation patterns of a reflector antenna from either a measured or computed feed pattern are reported. The reflector is defined by the intersection of a cone with any surface of revolution or an offset sector of any surface of revolution. The feed is assumed to be linearly polarized and can have an arbitrary location. Both the copolarized and the cross-polarized reflector radiation patterns are computed. Calculations using the technique compare closely with measured radiation patterns of a waveguide-fed offset parabolic reflector. Unique features of this technique are freedom from restrictive feed assumptions and the numerical methods used in preparing the aperture-plane electric-field data for integration.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation; AP-24; Jan. 197
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  • 16
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    Use of a multi-look unfocussed SAR processor on spacecraft (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Two methods of processing signals from a multi-look unfocussed synthetic-aperture radar are considered. A saving in the processor complexity is achieved in comparison to a fully focussed SAR system at the expense of slightly greater clutter levels and poorer along-track resolution. In addition, lower power consumption enables the unfocussed processor to increase the number of looks to compensate in part for the reduced resolution.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-156721 , RSL-TM-295-10
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  • 17
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    Evaluation of S-Band FM Direct Link Signal and System Design (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The adequacy of the S-band FM downlink as part of space shuttle orbiter communication links, was assessed to satisfy all known requirements during all mission phases. Some potential performance problems are described and corrective actions are recommended when appropriate.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-151584 , R7609-3
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  • 18
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    Frequency band justifications for passive sensors 10.0 to 385 GHz, chapter 1 (1976)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: For abstract, see N78-15327.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-155530
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  • 19
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    Frequency band justifications for passive sensors 10.0 to 385 GHz, chapter 2 (1976)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: Sensitivity requirements of the various measurements obtained by microwave sensors, and radiometry techniques are described. Analytical techniques applied to detailed sharing analyses are discussed. A bibliography of publications pertinent to the scientific justification of frequency requirements for passive microwave remote sensing is included.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-155532
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  • 20
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    Frequency band justifications for passive sensors, 1 to 10 GHz (1976)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: Remote sensor systems operating in the microwave region of the frequency spectrum provide information unobtainable with basic imaging techniques such as photography, television, or multispectral imaging. The frequency allocation requirements for passive microwave sensors used in the earth exploration satellite and space research services are presented for: (1) agriculture, forestry, and range resources; (2) land use survey and mapping: (3) water resources; (4) weather and climate; (5) environmental quality; and (6) marine resources, estuarine and oceans. Because measurements are required simultaneously in multiple frequency bands to adequately determine values of some phenomena, the relationships between frequency bands are discussed. The various measurement accuracies, dynamic range, resolutions and frequency needs are examined. A band-by-band summary of requirements, unique aspects, and sharing analyses of the required frequency bands is included.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-155531
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  • 21
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    Radar systems for a polar mission, volume 3, appendices A-D, S, T (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Success is reported in the radar monitoring of such features of sea ice as concentration, floe size, leads and other water openings, drift, topographic features such as pressure ridges and hummocks, fractures, and a qualitative indication of age and thickness. Scatterometer measurements made north of Alaska show a good correlation with a scattering coefficient with apparent thickness as deduced from ice type analysis of stereo aerial photography. Indications are that frequencies from 9 GHz upward seem to be better for sea ice radar purposes than the information gathered at 0.4 GHz by a scatterometer. Some information indicates that 1 GHz is useful, but not as useful as higher frequencies. Either form of like-polarization can be used and it appears that cross-polarization may be more useful for thickness measurement. Resolution requirements have not been fully established, but most of the systems in use have had poorer resolution than 20 meters. The radar return from sea ice is found to be much different than that from lake ice. Methods to decrease side lobe levels of the Fresnel zone-plate processor and to decrease the memory requirements of a synthetic radar processor are discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-156641 , RSL-TR-291-2-VOL-3
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  • 22
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    Microwave remote sensing of a two-layer random medium (1976)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: A two-variable expansion technique is used to solve for the mean Green's. function from the Dyson equation under the nonlinear approximation. The Bethe-Salpeter equation then gives rise to a set of modified radiative transfer (MRT) equations which accommodate coherent effects essential to bounded media. It is found that the nonlinear approximation, instead of the more popular bilocal approximation, should be used for the case of bounded media. The two approximations yield identical results for unbounded media. The MRT equations are then solved for a two-layer random medium. The MRT equations give rise to simple and useful solutions which are applicable to both active and passive microwave remote sensing.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation; AP-24; May 1976
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  • 23
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    Attenuation diversity measurements at 20 and 30 GHz (1976)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The results of data obtained at The University of Texas at Austin in conjunction with the ATS-6 millimeter wave experiment are presented. Attenuation measurements at 30 GHz and sky noise data at 20 GHz were obtained for 93 days simultaneously at each of two sites separated by 11 km and for 314 days at one site. The ratio of the loss at 30 GHz to that at 20 GHz due to rain varied from about 2 to about 4 with a median value of 2.65. This value was used to estimate 30 GHz losses for the 38.6% of time during attenuation events for which the satellite link was not available. Space diversity reduced outage time for a system in Austin, Texas, with a 10 db fade margin at 30 GHz from 3.8 hours to 4.1 minutes for the 93 days. Extrapolated to a yearly base this corresponds to 15 hours and to 16 minutes respectively. A plot of maximum observed cloud height against maximum hourly attenuation indicates that for a given attenuation level a lower limit is set for the maximum cloud height.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Radio Science; 11; Mar. 197
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  • 24
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    Wavelength dependence in radio-wave scattering and specular-point theory (1976)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Radio-wave scattering from natural surfaces contains a strong quasispecular component that at fixed wavelengths is consistent with specular-point theory, but often has a strong wavelength dependence that is not predicted by physical optics calculations under the usual limitations of specular-point models. Wavelength dependence can be introduced by a physical approximation that preserves the specular-point assumptions with respect to the radii of curvature of a fictitious, effective scattering surface obtained by smoothing the actual surface. A uniform low-pass filter model of the scattering process yields explicit results for the effective surface roughness versus wavelength. Interpretation of experimental results from planetary surfaces indicates that the asymptotic surface height spectral densities fall at least as fast as an inverse cube of spatial frequency. Asymptotic spectral densities for Mars and portions of the lunar surface evidently decrease more rapidly.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Radio Science; 11; Feb. 197
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  • 25
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    Computer analysis speeds corrugated horn design (1976)
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    Publication Date: 2019-06-27
    Description: A computer analysis program is developed for selecting the optimum flare angle and horn length of a corrugated horn design, the horn diameter, and the radiation pattern, before resorting to machining operations. The calculated antenna pattern is best suited to narrowband designs, and averaging of the E and H planes is recommended for wideband work. The program language used is BASIC. Some design examples are provided with representative data, printouts, and a rundown of the equations programmed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: MicroWaves; 15; May 1976
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  • 26
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    Sharing criteria and performance standards for the 11.7-12.2 GHz band in region 2 (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Possible criteria for sharing between the broadcasting-satellite and the fixed-satellite services are considered for each of several parameters in three categories: system, space station, and earth station. Criteria for sharing between the two satellite services and the three terrestrial services to which the 12-GHz band is allocated are discussed separately, first for the case of the fixed and mobile services and then for the broadcasting service.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-148756 , JPL-SP-43-35
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  • 27
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    Computation of scalar far-field patterns of large-aperture antennas (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: In computer programs used for evaluating the performance of high-gain antennas, efficient numerical methods for calculating the far-field patterns must be used since the majority of computer time and storage requirements may be attributed to this phase of the program. The numerical method most frequently used is the Fast Fourier Transform (FFT), which computes the far field as the Fourier transform of the field distribution in the antenna aperture. A new numerical method that in many applications is superior to the FFT in terms of reducing computer time and storage requirements is described.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-X-3408 , E-8746
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  • 28
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    Shuttle synthetic aperture radar implementation study, volume 1 (1976)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: Results of an implementation study for a synthetic aperture radar for the space shuttle orbiter are described. The overall effort was directed toward the determination of the feasibility and usefulness of a multifrequency, multipolarization imaging radar for the shuttle orbiter. The radar is intended for earth resource monitoring as well as oceanographic and marine studies.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-147775 , JPL-750-73-VOL-1
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  • 29
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    Payload operation television system (1976)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: The Payload Operation Television System is a high performance closed-circuit TV system designed to determine the feasibility of using TV to augment purely visual monitoring of operations, and to establish optimum system design of an operating unit which can ultimately be used to assist the operator of a remotely manipulated space-borne cargo loading device. The TV system assembled on this program is intended for laboratory experimentation which would develop operational techniques and lead to the design of space-borne TV equipment whose purpose would be to assist the astronaut-operator aboard a space station to load payload components. The equipment consists principally of a good quality TV camera capable of high resolving power; a TV monitor; a sync generator for driving camera and monitor; and two pan/tilt units which are remotely controlled by the operator.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-147777
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  • 30
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    Communications and tracking subsystem approach and landing test phase task 501 RF path console acceptance test report (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The RF downlink S-band path in the RF path console was tested under quality assurance inspection. The UHF RF paths were also tested. The acceptance test plans, procedures, and results of the acceptance tests are included.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-147764 , LEC-8634 , JSC-11194
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  • 31
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    Design document for shuttle task 501. Shuttle carrier aircraft transceiver console (SED 36115353-301) (1976)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: The flight data for the space shuttle orbiter (SSO) is transmitted via S band to a transceiver in the shuttle carrier aircraft (SCA) for relay to the ground during the mated portion of the approach and landing test (ALT). The transceiver is mounted in the SCA transceiver console for shuttle task 501 testing. This document defines the requirements for the SCA transceiver console, the design description, test plan for the console prior to installating the spacecraft equipment in the console, and the test plan for acceptance tests.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-147765 , JSC-11086 , LEC-8246
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  • 32
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    Shuttle spectrum despreader (1976)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: The results of the spread spectrum despreader project are reported and three principal products are designed and tested. The products are, (1) a spread spectrum despreader breadboard, (2) associated test equipment consisting of a spectrum spreader and bit reconstruction/error counter and (3) paper design of a Ku-band receiver which would incorporate the despreader as a principal subsystem. The despreader and test set are designed for maximum flexibility. A choice of unbalanced quadriphase or biphase shift keyed data modulation is available. Selectable integration time and threshold voltages on the despreader further lend true usefulness as laboratory test equipment to the delivered hardware.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-147749 , TRW-28453 , CDRL-0002
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  • 33
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    Analysis of aircraft wing-mounted antenna patterns (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: High frequency radiation patterns of aircraft wing mounted antennas are analyzed. Basic antenna types using ray optical techniques are studied. The aircraft is modelled in its most basic form so that this study is applicable to general type aircraft. The fuselage is modelled as a perfectly conducting finite elliptic cylinder. The wings and horizontal and vertical stabilizers are modelled as perfectly conducting "n" sided flat plates that can be arbitrarily attached to the fuselage or to themselves. The antenna locations are assumed to be on the surfaces of the wings at locations removed from engines and stores such that these effects are negligible. Volumetric patterns are calculated for several aircraft. The validity of the solution is shown by comparing the results against scale model measurements. The application of this solution to practical airborne antenna problems has shown its versatility in designing antennas and predicting their radiation patterns in an accurate and efficient manner.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-148199 , TR-2902-25
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    Volumetric pattern analysis of fuselage-mounted airborne antennas (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A volumetric pattern analysis of fuselage-mounted airborne antennas at high frequencies was investigated. The primary goal of the investigation was to develop a numerical solution for predicting radiation patterns of airborne antennas in an accurate and efficient manner. An analytical study of airborne antenna pattern problems is presented in which the antenna is mounted on the fuselage near the top or bottom. Since this is a study of general-type commercial aircraft, the aircraft was modeled in its most basic form. The fuselage was assumed to be an infinitely long perfectly conducting elliptic cylinder in its cross-section and a composite elliptic cylinder in its elevation profile. The wing, cockpit, stabilizers (horizontal and vertical) and landing gear are modeled by "N" sided bent or flat plates which can be arbitrarily attached to the fuselage. The volumetric solution developed utilizes two elliptic cylinders, namely, the roll plane and elevation plane models to approximate the principal surface profile (longitudinal and transverse) at the antenna location. With the belt concept and the aid of appropriate coordinate system transformations the solution can be used to predict the volumetric patterns of airborne antennas in an accurate and efficient manner. Applications of this solution to various airborne antenna problems show good agreement with scale model measurements. Extensive data are presented for a microwave landing antenna system.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-147099 , TR-2902-24
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    Ku band low noise parametric amplifier (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A low noise, K sub u-band, parametric amplifier (paramp) was developed. The unit is a spacecraft-qualifiable, prototype, parametric amplifier for eventual application in the shuttle orbiter. The amplifier was required to have a noise temperature of less than 150 K. A noise temperature of less than 120 K at a gain level of 17 db was achieved. A 3-db bandwidth in excess of 350 MHz was attained, while deviation from phase linearity of about + or - 1 degree over 50 MHz was achieved. The paramp operates within specification over an ambient temperature range of -5 C to +50 C. The performance requirements and the operation of the K sub u-band parametric amplifier system are described. The final test results are also given.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-147560 , C362-1
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    Comparison of rate one-half, equivalent constraint length 24, binary convolutional codes for use with sequential decoding on the deep-space channel (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Virtually all previously-suggested rate 1/2 binary convolutional codes with KE = 24 are compared. Their distance properties are given; and their performance, both in computation and in error probability, with sequential decoding on the deep-space channel is determined by simulation. Recommendations are made both for the choice of a specific KE = 24 code as well as for codes to be included in future coding standards for the deep-space channel. A new result given in this report is a method for determining the statistical significance of error probability data when the error probability is so small that it is not feasible to perform enough decoding simulations to obtain more than a very small number of decoding errors.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-146846 , EE-762
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    Payload operation television system (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The TV system assembled is intended for laboratory experimentation which would develop operational techniques and lead to the design of space-borne TV equipment whose purpose would be to assist the astronaut-operator aboard a space station to load payload components. The TV system assembled for this program is a black and white, monocular, high performance system. The equipment consists principally of a good quality TV camera capable of high resolving power; a TV monitor; a sync generator for driving camera and monitor; and two pan/tilt units which are remotely controlled by the operator. One pan/tilt unit provides control of the pointing of the camera, the other similarly controls the position of a simulated payload.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-147534
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    A global search and rescue concept using synthetic aperture radar and passive user targets (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A terrestrial search and rescue concept is defined embodying the use of passive radio-frequency reflectors in conjunction with an orbiting synthetic aperture radar to detect, identify, and locate users. An airborne radar test was conducted to evaluate the basic concept. In this test simple corner-reflector targets were successfully imaged. Results from this investigation were positive and indicate that the concept can be used to investigate new approaches focused on the development of a global search and rescue system.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TN-D-8172 , L-10259
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    Filtering device (1976)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: An electrical filter for removing noise from a voice communications signal is reported; seven sample values of the signal are obtained continuously, updated and subjected to filtering. Filtering is accomplished by adding balanced, with respect to a mid-point sample, spaced pairs of the sampled values, and then multiplying each pair by a selected filter constant. The signal products thus obtained are summed to provide a filtered version of the original signal.
    Keywords: COMMUNICATIONS AND RADAR
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    Highly efficient antenna system using a corrugated horn and scanning hyperbolic reflector (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: In a horn-reflector antenna system for producing a spherical aperture phase front, a corrugated conical horn illuminates a section of a hyperbolic reflector to produce a spherical aperture phase front. This front produces a far field beam with low sidelobes and high beam efficiency. The system is insensitive to frequency and polarization changes, and is also insensitive to orientation about the axis of the conical horn for beam scanning.
    Keywords: COMMUNICATIONS AND RADAR
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    Study of low frequency hydromagnetic waves using ATS-1 data (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Low frequency oscillations of the magnetic field at ATS-1 were analyzed for the 25 month data interval, Dec., 1966 through 1968. Irregular oscillations and those associated with magnetic storms were excluded from the analysis. Of the 222 events identified, 170 were found to be oscillating predominantly transverse to the background magnetic field. The oscillations were observed to occur most frequently in the early afternoon hours. They also seemed to occur more frequently during Dec., Jan., and Feb. than at any other time of the year. During a given event, the frequency was fairly constant. The event duration varied between a minimum of 10 min. and a maximum of 14 hrs and 26 min. During a given event the amplitude varied.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-148580
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    Study to investigate and evaluate means of optimizing the radar function for the space shuttle (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A detailed analysis of the spiral scan was performed for antenna sizes ranging from 20 inches to 36 inches in diameter and for search angles characteristic of both the radar and the communication acquisition modes. The power budgets for passive target radar detection were calculated for antenna diameters ranging from 20 to 36 inches. Dwell times commensurate with spiral scan were used for these budget calculations. The signal design for the candidate pulse Doppler system is summarized. Ground return analysis carried out for the passive target radar mode is examined, and the details are presented. A concluding description of the proposed candidate radar/communication system configuration is given.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-147842 , R7607-4
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    KIM-1 interface adapter to 3-wire teletype systems (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The KIM-1 circuit designed for use with a full duplex isolated 4 terminal system is described. Operation of the circuit with a 3 wire system in conjunction with a single +5v supply interface is discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-148768 , TM-38
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    The NASA teleconferencing system: An evaluation (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The communication requirements of the Apollo project led to the development of a teleconferencing network which linked together, in an audio-fax mode, the several NASA centers and supporting contractors of the Apollo project. The usefulness of this communication linkage for the Apollo project suggested that the system might be extended to include all NASA centers, enabling them to conduct their in-house business more efficiently than by traveling to other centers. A pilot project was run in which seventeen NASA center and subcenters, some with multiple facilities, were connected into the NASA teleconferencing network. During that year, costs were charted and, at the end of the year, an evaluation was made to determine how the system had been used and with what results. The year-end evaluation of the use of NASA teleconferencing system is summarized.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-X-74160
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    On signal design by the R sub 0 criterion for non-white Gaussian noise channels (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The use of the R sub 0 criterion for modulation system design is investigated for channels with non-white Gaussian noise. A signal space representation of the waveform channel is developed, and the cut-off rate R sub 0 for vector channels with additive nonwhite Gaussian noise and unquantized demodulation is derived. When the signal unput to the channel is a continuous random vector, maximization of R sub 0 with constrained average signal energy leads to a water-filling interpretation of optimal energy distribution in signal space. The necessary condition for a finite signal set to maximize R sub 0 with constrained energy and an equally likely probability assignment of signal vectors is presented, and an algorithm is outlined for numerically computing the optimum signal set. A necessary condition on a constrained energy, finite signal set is found which maximizes a Taylor series approximation of R sub 0. This signal set is compared with the finite signal set which has the water-filling average energy distribution.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-148532 , TR-EE-768
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    Study and simulation of spatial video compression for remotely piloted vehicles (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Techniques of video compression applicable to remotely piloted vehicles (RPVs) are investigated. One approach is to reduce the frame rate, the other is to reduce the number of bits per sample needed to represent static picture detail by means of digital video compression. Hadamard transforms of 8 x 8 subpictures, with adaptive and nonadaptive quantization of transform coefficients, were investigated for the latter technique. Tapes of typical RPV video, processed by Aeronautronic Ford to simulate four frame rates, were again processed by the Ames real-time video system to obtain a variety of compressions of each of the four frame rates.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-X-73137 , A-6615
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    Research in large adaptive antenna arrays (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The feasibility of microwave holographic imaging of targets near the earth using a large random conformal array on the earth's surface and illumination by a CW source on a geostationary satellite is investigated. A geometrical formulation for the illuminator-target-array relationship is applied to the calculation of signal levels resulting from L-band illumination supplied by a satellite similar to ATS-6. The relations between direct and reflected signals are analyzed and the composite resultant signal seen at each antenna element is described. Processing techniques for developing directional beam formation as well as SNR enhancement are developed. The angular resolution and focusing characteristics of a large array covering an approximately circular area on the ground are determined. The necessary relations are developed between the achievable SNR and the size and number of elements in the array. Numerical results are presented for possible air traffic surveillance system. Finally, a simple phase correlation experiment is defined that can establish how large an array may be constructed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-148135 , VFRC-86
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    ATS-6 spacecraft: In-flight antenna pattern measurement (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Antenna patterns, principally associated with the 9.1 meter parabolic antenna of the ATS-6 spacecraft, were measured while in orbit at quasi-stationary synchronous altitude. Controlling the spacecraft attitude permitted a scanning of the spacecraft antenna pattern over the Rosman ground station, thus achieving the measurement of the antenna pattern contour. Patterns were determined in terms of relative gain referenced in position to the spacecraft body coordinates by means of signal power measurements made using a linear detector. These data were subsequently correlated with the attitude data to define the antenna patterns. Antenna patterns measured are presented and compared with available preflight patterns.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TN-D-8135 , G-7614
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    ATS-F Comsat millimeter wave propagation experiment data analysis report, part 2 (1976)
    In:  CASI
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    Publication Date: 2019-06-27
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-152450
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    Tracker implementation for the orbiter Ku-band communications antenna (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Possible implementations and recommendations for the Space Shuttle Ku-Band integrated communications/radar antenna tracking system were evaluated. Communication aspects involving the Tracking Data Relay Satellite (TDRS)/Orbiter Ku-Band link are emphasized. Detailed analysis of antenna sizes, gains and signal-to-noise ratios shows the desirability of using maximum size 36-inch diameter dish and a triple channel monopulse. The use of the original baselined 20 inch dish is found to result in excessive acquisition time since the despread signal would be used in the tracking loop. An evaluation of scan procedures which includes vehicle dynamics, designation error, time for acquisition and probability of acquisition shows that the conical scan is preferred since the time for lock-on for relatively slow look angle rates will be significantly shorter than the raster scan. Significant improvement in spherical coverage may be obtained by reorienting the antenna gimbal to obtain maximum blockage overlap.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-150992 , DN-B0603-007
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    Satellite Instructional Television Experiment (SITE): Reports from the NASA resident representative in India (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Reports submitted by the NASA project representative for the Satellite Instructional Television Experiment (SITE) at Ahmedabad, India are presented. These reports deal with the coordination of all SITE related matters between the ATS 6 Project at Goddard Space Flight Center, NASA Headquarters, and the SITE Program in India.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-X-74146
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    High rate bit synchronizer (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: This report documents the analysis and experimental validation of the performance of various aspects of a high rate bit synchronizer.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-147881 , STI-TR-4166
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    Integrated source and channel encoded digital communication system design study (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The results of several studies Space Shuttle communication system are summarized. These tasks can be divided into the following categories: (1) phase multiplexing for two- and three-channel data transmission, (2) effects of phase noise on the performance of coherent communication links, (3) analysis of command system performance, (4) error correcting code tradeoffs, (5) signal detection and angular search procedure for the shuttle Ku-band communication system, and (6) false lock performance of Costas loop receivers.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-147880 , R7607-3
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    Real time analysis of voiced sounds (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A power spectrum analysis of the harmonic content of a voiced sound signal is conducted in real time by phase-lock-loop tracking of the fundamental frequency, (f sub 0) of the signal and successive harmonics (h sub 1 through h sub n) of the fundamental frequency. The analysis also includes measuring the quadrature power and phase of each frequency tracked, differentiating the power measurements of the harmonics in adjacent pairs, and analyzing successive differentials to determine peak power points in the power spectrum for display or use in analysis of voiced sound, such as for voice recognition.
    Keywords: COMMUNICATIONS AND RADAR
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    Rendezvous radar modification and evaluation (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The purpose of this effort was to continue the implementation and evaluation of the changes necessary to add the non-cooperative mode capability with frequency diversity and a doppler filter bank to the Apollo Rendezvous Radar while retaining the cooperative mode capability.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-147879
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    New optical and radio frequency angular tropospheric refraction models for deep space applications (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The development of angular tropospheric refraction models for optical and radio frequency usage is presented. The models are compact analytic functions, finite over the entire domain of elevation angle, and accurate over large ranges of pressure, temperature, and relative humidity. Additionally, FORTRAN subroutines for each of the models are included.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-148534 , JPL-TR-32-1601
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    Measurements of wave height statistics and radar, cross-section in a wind wave tank (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: There is currently wide interest among oceanographers and meteorologists in remote sensing of ocean surface characteristics. A wind wave tank developed at Langley Research Center is used to evaluate various remote sensing techniques based on electromagnetic scattering phenomena, and in the development and evaluation of theoretical scattering models. The wave tank is described, the statistics of the rough water surface are documented, and microwave radar cross-section measurement results are presented. The water surface statistics are similar in key respects to the open ocean, and the microwave scattering measurements show, qualitatively, theoretically predicted large and small scale scattering effects.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-X-72834
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    Space shuttle Ku-band integrated rendezvous radar/communications system study (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The results are presented of work performed on the Space Shuttle Ku-Band Integrated Rendezvous Radar/Communications System Study. The recommendations and conclusions are included as well as the details explaining the results. The requirements upon which the study was based are presented along with the predicted performance of the recommended system configuration. In addition, shuttle orbiter vehicle constraints (e.g., size, weight, power, stowage space) are discussed. The tradeoffs considered and the operation of the recommended configuration are described for an optimized, integrated Ku-band radar/communications system. Basic system tradeoffs, communication design, radar design, antenna tradeoffs, antenna gimbal and drive design, antenna servo design, and deployed assembly packaging design are discussed. The communications and radar performance analyses necessary to support the system design effort are presented. Detailed derivations of the communications thermal noise error, the radar range, range rate, and angle tracking errors, and the communications transmitter distortion parameter effect on crosstalk between the unbalanced quadriphase signals are included.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-147583 , D4148 , SCG-60041R
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    Prototype 10-meter radio telescope antenna and mount design (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A prototype radio antenna of 10.4 meters diameter and 0.41 meter focal length, intended for use at the shortest radio wavelengths transmitted by the atmosphere, was successfully completed. The surface accuracy is at least four times better than that of any existing antenna in this size class: 50 micrometer rms. A prototype mount is being constructed and will be ready by early 1976. The development of an improved antenna of identical size, but heavier weight has been continued.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-146305
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    Solid state, CCD-buried channel, television camera study and design (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: An investigation of an all solid state television camera design, which uses a buried channel charge-coupled device (CCD) as the image sensor, was undertaken. A 380 x 488 element CCD array was utilized to ensure compatibility with 525 line transmission and display monitor equipment. Specific camera design approaches selected for study and analysis included (a) optional clocking modes for either fast (1/60 second) or normal (1/30 second) frame readout, (b) techniques for the elimination or suppression of CCD blemish effects, and (c) automatic light control and video gain control techniques to eliminate or minimize sensor overload due to bright objects in the scene. Preferred approaches were determined and integrated into a design which addresses the program requirements for a deliverable solid state TV camera.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-147839 , ED-AX-75
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    Carrier and symbol synchronization system performance study (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Results pertinent to predicting the performance of convolutionally encoded binary phase-shift keyed communication links were presented. The details of the development are provided in four sections. These sections are concerned with developing the bit error probability performance degradations due to PN despreading by a time-shared delay locked loop, the Costas demodulation process, symbol synchronization effects and cycle slipping phenomena in the Costas loop. In addition, Costas cycle slipping probabilities are studied as functions of Doppler count time and signal-to-noise conditions. The effect of cycle slipping in the symbol synchronizer is also studied as a function of channel Doppler and other frequency uncertainties.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-147662 , TR-04-7508-9
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    Twenty and thirty GHz millimeter wave experiments with the ATS-6 satellite (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Studies at 11 locations in the continental United States were directed at an evaluation of rain attenuation effects, scintillations, depolarization, site diversity, coherence bandwidth, and analog and digital communications techniques using the Applications Technology Satellite-6(ATS-6). In addition to direct measurements on the 20- and 30-GHz links, methods of attenuation prediction with radars, rain gages, and radiometers were developed and compared with the directly measured attenuation. Initial data results of the ATS-6 millimeter wave experiment were presented. The first section describes the experiment objectives, flight hardware, and modes of operation. The remaining six sections present papers prepared by the major participating organizations in the experiment. The papers present a comprehensive summary of the significant results of the initial 11 months of ATS-6 experiment measurements and related radiometric, radar, and radio-meteorology studies.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TN-D-8197 , G-7649
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    Automatic noise limiter-blanker (1976)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: A blanker system that may be used with audio noise limiters or automatic noise limiters was described. The system employs a pair of silicon diodes and two RC filters connected across the feedback impedance of an operational amplifier so as to counteract impulse noise interference caused by local spherics activity or 60 Hz harmonics radiated from ac motor control systems. The following information is given: circuit diagram and description, operating details, evaluation, discussion of other noise blanking methods.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-147161 , TM-27
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    Solid state television camera (1976)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: The design, fabrication, and tests of a solid state television camera using a new charge-coupled imaging device are reported. An RCA charge-coupled device arranged in a 512 by 320 format and directly compatible with EIA format standards was the sensor selected. This is a three-phase, sealed surface-channel array that has 163,840 sensor elements, which employs a vertical frame transfer system for image readout. Included are test results of the complete camera system, circuit description and changes to such circuits as a result of integration and test, maintenance and operation section, recommendations to improve the camera system, and a complete set of electrical and mechanical drawing sketches.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-147494
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    Investigations of electromagnetic scattering by columnar ice crystals (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: An integral equation approach was developed to determine the scattering and absorption of electromagnetic radiation by thin walled cylinders of arbitrary cross-section and refractive index. Based on this method, extensive numerical data was presented at infrared wavelengths for hollow hexagonal cross section cylinders which simulate columnar sheath ice crystals.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-146327 , UMICH-013381-1-F
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    The effects of an ion-thruster exhaust plume on S-band carrier transmission (1976)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: The magnitude of the effects of an ion thruster plume on S-band signals is measured. Modeling techniques are developed to predict the effects. Results show that the RF signal transmitted through an ion thruster plume is reduced in amplitude and shifted in phase. An increase in noise is also experienced.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-145919 , JPL-TM-33-754
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    Path attenuation statistics influenced by orientation of rain cells (1976)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The influence of path azimuth on fade and space diversity statistics associated with propagation along earth-satellite paths at a frequency of 18 GHz is examined. A radar rain reflectivity data base obtained during the summer of 1973 is injected into a modeling program and the attenuation along parallel earth-satellite paths are obtained for a conglomeration of azimuths. Statistics are separated into two groupings: one pertaining to earth-satellite paths oriented in the northwest-southeast and the other in the northeast-southwest quadrants using a fixed elevation angle of 45 deg. The latter case shows fading to be greater with a degraded space diversity suggesting rain cells to be elongated along this direction. Cell dimensions are analyzed for both sets of quadrants and are found to have average values larger by 2 km in the northeast-southwest quadrants; a result consistent with the fade and space diversity results. Examination of the wind direction for the 14 rain days of data analyzed shows good correlation of the average or median wind directions with the directions of maximum fading and degraded space diversity.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation; AP-24; Nov. 197
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  • 68
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    Attenuation of propagation through rain for an earth-satellite path correlated with predicted values using radar (1976)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: During the summer of 1974 and spring of 1975, measurements of attenuation of propagation through rain were made at Wallops Island, VA, using 13 and 18 GHz transmitters operating in the uplink mode toward the ATS-6 satellite. Simultaneously, rain reflectivity levels were measured along the earth-satellite path using a high resolution (0.4 deg beamwidth) S-band radar having a scanning antenna. Four rain-gages and two disdrometers were also located in the vicinity of the transmitters. The radar and disdrometer data were used in a modelling program to predict attenuation levels which were subsequently compared to the directly measured fades over nearly simultaneous time intervals. Predicted attenuation levels were obtained for three drop size distributions. Comparisons between predicted and measured attenuation levels showed the APL dropsize distribution gave the smallest rms difference of 1.3 dB at 13 and 18 GHz although the rms difference corresponding to Marshall-Palmer was close to this value. The good agreement suggests the validity of using radar to model path attenuation to obtain attenuation statistics.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation; AP-24; Nov. 197
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  • 69
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    Feasibility of Coherent and Incoherent Backscatter Experiments from the AMPS Laboratory. Summary Section (1976)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: For abstract, see N77-10397.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-144338 , SSL-SER-17-ISSUE-35
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  • 70
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    Comments on 'Scattering of electromagnetic waves from a tilted slightly rough surface' (1976)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Keywords: COMMUNICATIONS AND RADAR
    Type: Radio Science; 11; Aug
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  • 71
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    A fast Karhunen-Loeve transform for a class of random processes (1976)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: It is shown that for a class of finite first-order Markov signals, the Karhunen-Loeve (KL) transform for data compression is a set of periodic sine functions if the boundary values of the signal are fixed or known. These sine functions are shown to be related to the Fourier transform so that a fast Fourier transform algorithm can be used to implement the KL transform. Extension to two dimensions with reference to images with separable contravariance function is shown.
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  • 72
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    Techniques for correcting transmission errors in video adaptive delta modulation channels (1976)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: We investigated the effects of channel errors on an adaptive delta modulator used to encode video signals. The investigation revealed that channel errors caused a permanent shift in the dc level of the delta modulator's estimate. Errors in the step size, on the other hand, were transitory and had no noticeable effect on the received pictures. We then presented three error correction schemes to minimize the visibility of the channel errors in the received picture. The first scheme required the transmitter to periodically send the correct dc level of the estimate to the receiver. The second method employed a leaky integrator, and the third method used line-to-line interpolation
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Communications; COM-24; Sept
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  • 73
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    An MSK approach to offset QASK (1976)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: This paper demonstrates that an offset quadrature amplitude-shift-keyed (OQASK) signal can be represented as an n-component version of a minimum-shift-keyed (MSK) signal. For example, the signal set obtained by summing two MSK signals which are 6 dB different in power and are formed by continuous phase, frequency modulating the same oscillator with two independent binary antipodal data streams, is spectrally equivalent to an OQASK signal set composed of 16 signals in which the symbol pulse is a half-cycle sinusoid rather than the conventional rectangular form. Such generalizations as the above allow for potentially simpler implementation of spectrally shaped OQASK.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Communications; COM-24; Aug. 197
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  • 74
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    Partial correlation properties of pseudonoise /PN/ codes in noncoherent synchronization/detection schemes (1976)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: This concise paper considers the effect on the autocorrelation function of a pseudonoise (PN) code when the acquisition scheme only integrates coherently over part of the code and then noncoherently combines these results. The peak-to-null ratio of the effective PN autocorrelation function is shown to degrade to the square root of n, where n is the number of PN symbols over which coherent integration takes place.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Communications; COM-24; Aug. 197
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  • 75
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    A generalization of minimum-shift-keying /MSK/-type signaling based upon input data symbol pulse shaping (1976)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Communications; COM-24; Aug. 197
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  • 76
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    Performance analysis of digital FM demodulators for fading channels in the threshold region (1976)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The quasi-optimum digital FM demodulators for fading channels reported earlier (1975) reflected the system performance accurately under high signal to noise ratio conditions. In this paper, the prediction of the system performance for low SNR values is considered. A new set of error variance algorithms is developed from the filter algorithm assuming a Gaussian distribution for the state estimation errors and taking the effect of high frequency terms into consideration. Simulation analysis for an FM system with Rician fading channel shows that these algorithms predict the system performance accurately in the threshold region.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Computers and Electrical Engineering; 3; June 197
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  • 77
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    On optimal soft-decision demodulation (1976)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: A necessary condition is derived for optimal J-ary coherent demodulation of M-ary (M greater than 2) signals. Optimality is defined as maximality of the symmetric cutoff rate of the resulting discrete memoryless channel. Using a counterexample, it is shown that the condition derived is generally not sufficient for optimality. This condition is employed as the basis for an iterative optimization method to find the optimal demodulator decision regions from an initial 'good guess'. In general, these regions are found to be bounded by hyperplanes in likelihood space; the corresponding regions in signal space are found to have hyperplane asymptotes for the important case of additive white Gaussian noise. Some examples are presented, showing that the regions in signal space bounded by these asymptotic hyperplanes define demodulator decision regions that are virtually optimal.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Information Theory; IT-22; July 197
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  • 78
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    Syndrome-source-coding and its universal generalization (1976)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: A method of using error-correcting codes to obtain data compression, called syndrome-source-coding, is described in which the source sequence is treated as an error pattern whose syndrome forms the compressed data. It is shown that syndrome-source-coding can achieve arbitrarily small distortion with the number of compressed digits per source digit arbitrarily close to the entropy of a binary memoryless source. A 'universal' generalization of syndrome-source-coding is formulated which provides robustly effective distortionless coding of source ensembles. Two examples are given, comparing the performance of noiseless universal syndrome-source-coding to (1) run-length coding and (2) Lynch-Davisson-Schalkwijk-Cover universal coding for an ensemble of binary memoryless sources.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Information Theory; IT-22; July 197
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  • 79
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    Basic limits on protocol information in data communications networks (1976)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The paper considers basic limitations on the amount of protocol information that must be transmitted in a data communication network to keep track of source and receiver addresses and of the starting and stopping of messages. Assuming Poisson message arrivals between each communicating source-receiver pair, a lower bound is found on the required protocol information for message. This lower bound is the sum of two terms, one for the message-length information, which depends only on the distribution of message lengths, and the other for the message-start information, which depends only on the product of the source-receiver pair arrival rate and the expected delay for transmitting the message. Two strategies are developed which, in the limit of large numbers of sources and receivers, almost meet the lower bound on protocol information.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Information Theory; IT-22; July 197
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  • 80
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    A real time, low cost, data acquisition telecommunication network (1976)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: The real time, low cost data acquisition communication network described features the use of asynchronous ASCII code transmissions operating at 30 characters per second on the dial-up telephone system. The network features an elaborate, but easily generated error checking system, operating in a line-by-line demand-response mode. The system is readily adaptable for any low speed computer-to-computer data transmissions requiring high reliability in data transmission. The network was developed for the acquisition of prelaunch wind data from the Eastern Test Range at Cape Kennedy.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-X-73645 , E-9151
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  • 81
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    The 10 micrometer transmitter (1976)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: The design, fabrication tests, and engineering model components of a 10.6 mum wideband transceiver system are reported. The effort emphasized the transmitter subsystem, including the development of the laser, the modulator driver, and included productization of both the transmitter and local oscillator lasers. The transmitter subsystem is functionally compatible with the receiver engineering model terminal, and has undergone high data rate communication system testing against that terminal.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-152489 , D0460 , SCG-60517R
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  • 82
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    InSb arrays with CCD readout for 1.0- to 5.5-microns infrared applications (1976)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: There were two approaches for fabricating indium antimonide (InSb) arrays with CCD readout discussed. The hybrid approach integrated InSb detectors and silicon CCDs in a modular assembly via an advanced interconnection technology. In the monolithic approach, the InSb infrared detectors and the CCD readout were integrated on the same InSb chip. Both approaches utilized intrinsic (band-to-band) photodetection with the attendant advantages over extrinsic detectors. The status of each of these detector readout concepts, with pertinent performance characteristics, was presented.
    Keywords: COMMUNICATIONS AND RADAR
    Type: JPL Conf. on Charge-Coupled Device Technol. and Appls.; p 49-56
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  • 83
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    Fourier analysis computer-aided design of CCD signal processing analog multiplier arrays (1976)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The design of MOS multipliers with CAD was studied. In particular the Fourier analysis capability of the CAD program was used to analyze the harmonic distortion rejection, DR, of the multiplier.
    Keywords: COMMUNICATIONS AND RADAR
    Type: JPL Conf. on Charge-Coupled Device Technol. and Appls.; p 33-44
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  • 84
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    Orbiter KU-band transmitter (1976)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: The design, build, and test of an engineering breadboard Ku band quadraphase shift keyed and wideband frequency modulated transmitter are described. This orbiter Ku band transmitter drawer is to simulate the orbiter transmitter and meet the functional requirements of the orbiter communication link.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-151156 , PIA-2216
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  • 85
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    Feasibility of an Incoherent-scatter Radar Aboard the Space Shuttle (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The results of a preliminary study to investigate the feasibility of conducting an incoherent scatter radar experiment on board the space shuttle are presented. The results indicate that such an experiment is technically feasible. The more difficult questions to answer are whether the system can be made flexible enough to justify the problems and costs involved. The design parameters and the tradeoffs that are available in the consideration of these questions are evaluated. Some of the more serious limitations pertain to: (1) the presence of ground clutter and F region auroral clutter; (2) available average power; (3) weight and volume associated with required antenna size, transmitter, and energy storage devices; and (4) antenna breakdown associated with high power transmitter problems.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-144336
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  • 86
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    Emissivity of half-space random media (1976)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Scattering of electromagnetic waves by a half-space random medium with three-dimensional correlation functions is studied with the Born approximation. The emissivity is calculated from a simple integral and is illustrated for various cases. The results are valid over a wavelength range smaller or larger than the correlation lengths.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Radio Science; 11; July 197
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  • 87
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    Thermal microwave emission from half-space random media (1976)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Brightness temperatures resulting from microwave thermal emission from a half-space random medium are calculated. The random medium has a nonuniform temperature profile and is characterized by correlation functions that possess both vertical and lateral variations. Radiative transfer equations are derived. They are solved with an iterative integral equation approach for small scattering albedo and with a numerical approach for general cases. New results are illustrated, discussed, and compared with various special cases. Phenomena caused by resonant scattering, which is absent under Rayleigh approximations, are revealed. Scattering in the lateral direction contributes to the decrease of the equivalent reflectivity and the increase of the brightness temperature.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Radio Science; 11; July 197
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  • 88
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    Comparison of bit synchronization schemes using AM and summed clocks (1976)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: This paper considers bit synchronization through the use of a separate clock signal which is either amplitude modulated onto or summed with the data signal. For continuous data transmission, such schemes are known to be inferior, in the sense of efficient use of power, to schemes which derive synchronization directly from the data signal. However, these techniques have application in burst systems such as spacecraft command systems, and in systems where receiver simplicity is more important than power conservation. For systems in which the composite data-clock signal subsequently modulates an RF carrier, it is shown that the summed clock signal performs slightly better than the AM clock signal, and that for both signal types, the optimum allocation of power between data and clock is approximately 9:1.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Aerospace and Electronic Systems; AES-12; Mar. 197
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  • 89
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    Coding for a multiple-access channel (1976)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: In a simple multiple-access communication system, two geographically separated users attempt to communicate binary data to two data sinks over a common channel called a multiple access channel. User one sends codewords from a block code C sub one, while user two sends codewords from a block code C sub two. The two users occupy the same frequency slot, transmit at the same time, and use the same type of modulation. Block codes which are uniquely decodable and capable of correcting errors are constructed for two multiple-access channel models. The first model is referred to as a noiseless multiple-access binary erasure channel. If the two transmitted bits from the two users are zeros, a zero is transmitted over the channel to the receiver; if the two transmitted bits are ones, a one is transmitted to the receiver; if the two bits are different, an erasure symbol is transmitted to the receiver. The second model is also a multiple-access binary erasure channel but with noise introduced.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Information Theory; IT-22; Mar. 197
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  • 90
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    Dielectric coated wire antennas (1976)
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    Publication Date: 2019-06-27
    Description: An electrically thin dielectric insulating shell on an antenna composed of electrically thin circular cylindrical wires is examined. A moment method solution is obtained, and the insulating shell is modeled by equivalent volume polarization currents. These polarization currents are related in a simple manner to the surface charge density on the wire antenna. In this way the insulating shell causes no new unknowns to be introduced, and the size of the impedance matrix is the same as for the uninsulated wires. The insulation is accounted for entirely through a modification of the symmetric impedance matrix. This modification influences the current distribution, impedance, efficiency, field patterns, and scattering properties. The theory is compared with measurement for dielectric coated antennas in air.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Radio Science; 11; Jan. 197
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  • 91
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    Power spectra of sinusoidal amplitude-modulated binary signals (1976)
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    Publication Date: 2019-06-27
    Description: Power spectra for binary phase-shift keyed (PSK) and frequency-shift keyed (FSK) signals with combined sinusoidal amplitude modulation by the bit rate clock are presented. Such signal formats have application in 'burst' communication systems wherein reliable bit synchronization is provided with relative receiver simplicity. Effects of the clock amplitude modulation index and phase are considered, and corresponding power spectra are illustrated. Further, effects of the clock parameters on the rate of spectral rolloff are given and compared with those of conventional PSK and FSK spectra.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Communications; COM-24; Feb. 197
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  • 92
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    Locate and rescue system components (1976)
    In:  CASI
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    Publication Date: 2019-07-20
    Description: Two types of search and rescue systems not involving satellites are studied; one using a network radio communications link and the other a characteristic beacon signal. Line of slight limitation of VHF radio and beacon signals limit the range (approximately 25 miles) between the origin of the distress signal and the mobile rescue unit.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-144836
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  • 93
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    A depolarization and attenuation experiment using the CTS satellite. Volume 1: Experiment description (1976)
    In:  CASI
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    Publication Date: 2019-07-20
    Description: An experiment for measuring precipitation attenuation and depolarization on the Communications Technology Satellite (CTS) 11.7 GHz downlink is described. Attenuation and depolarization of the signal received from the spacecraft is monitored on a 24 hour basis. Data is correlated with ground weather conditions. Theoretical models for millimeter wave propagation through rain are refined for maximum agreement with observed data. Techniques are developed for predicting and mimimizing the effects of rain scatter and depolarization on future satellite communication systems.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-152422
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    Simulation of the reconstruction of distorted digital data (1976)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Results of simulation runs obtained while varying detector sampling rates and threshold levels for a 20,000 foot equalized cable and a bit rate of 1 Mbs are given. The simulation techniques appear useful for preliminary design of detector levels and sampling rates and for analyzing sensitivity of detector performance as system transfer function parameters are varied.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Midwest Symposium on Circuits and Systems; Aug 16, 1976 - Aug 17, 1976; Milwaukee, WI
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  • 95
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    A generalization of MSK-type signaling based upon input data symbol pulse shaping (1976)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Minimum-shift-keying (MSK), which is a special case of continuous phase frequency-shift-keying (CPFSK) with frequency deviation ratio equal to 0.5, is known to be spectrally equivalent to a form of offset quadrature phase-shift-keying (OQPSK) in which the symbol pulse shape is a half-cycle sinusoid rather than the usual rectangular form. Appropriate shaping of the input data symbols allows one to generate an entire class of constant envelope, MSK-type signals, whose spectral properties are in some applications more desirable than those of MSK or OQPSK. The present study derives and presents a set of conditions on the input pulse shaping which in turn describes the class of envelope shapes allowable. The autocorrelation function and power spectral density of this class of signals are then derived, and specific examples are given to illustrate the desirable spectral properties. Such properties are important considerations in system design where interchannel and intersymbol interference degradations must be kept to a minimum.
    Keywords: COMMUNICATIONS AND RADAR
    Type: International Conference on Communications; Jun 14, 1976 - Jun 16, 1976; Philadelphia, PA
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    United States societal experiments via the Communications Technology Satellite (1976)
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    Publication Date: 2019-07-13
    Description: After a brief description of the Communication Technology Satellite and its U.S. coverage, the U.S. societal experiments via the CTS are discussed. These include education (college curriculum sharing, and project interchange), health care (biomedical communications, health communications, and communication support for decentralized education), and community and special experiments (satellite library information network, and transportable earth terminal).
    Keywords: COMMUNICATIONS AND RADAR
    Type: International Conference on Communications; Jun 14, 1976 - Jun 16, 1976; Philadelphia, PA
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  • 97
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    Precipitation-attenuation studies based on measurements of ATS-6 20/30-GHz beacon signals at Clarksburg, Maryland (1976)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: Radiometric sky temperature and minute precipitation measurements were intended to broaden the data base required to advance the understanding of the propagation characteristics of the earth-satellite path at frequencies over 10 GHz. Analyses of the data collected from the measurement program have established a detailed correlation between the satellite signal and the signals from auxiliary ground-based measurements. The indirectly derived statistics agreed reasonably well (or can be reconciled) with the earlier published results. The correlations may therefore be used for indirectly estimating long term cumulative attenuation statistics in the absence of direct satellite signal measurements.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-152501 , CLP-74-110
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    Characteristics of magnetospheric radio noise spectra (1976)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Magnetospheric radio noise spectra (30 kHz to 10 MHz) taken by IMP-6 and RAE-2 exhibit time varying characteristics which are related to spacecraft position and magnetospheric processes. In the midfrequency range (100-1000 kHz) intense noise peaks rise a factor of 100 or more above background; 80% of the peak frequencies are within the band 125 kHz to 600 kHz, and the peak occurs most often (18% of the time) at 280 kHz. Bandwidths of the peaks range from about 100 kHz to more than 500 kHz; most often the lower cutoff is at about 100 kHz and the upper at 380 kHz for a total bandwidth of 280 kHz. This intense mid-frequency noise was detected at radial distances from 1.3 Re to 60 Re on all sides of the earth (i.e., all local times) during magnetically quiet as well as disturbed periods. Maximum occurrence of the mid-frequency noise is in the evening to midnight hours where splash-type energetic particle precipitation takes place.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-144843 , RSCR-76-1
    Format: application/pdf
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    Solid State Television Camera (CID) (1976)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The design, development and test are described of a charge injection device (CID) camera using a 244x248 element array. A number of video signal processing functions are included which maximize the output video dynamic range while retaining the inherently good resolution response of the CID. Some of the unique features of the camera are: low light level performance, high S/N ratio, antiblooming, geometric distortion, sequential scanning and AGC.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-151093
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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    CTS United States experiments - A progress report (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The Communications Technology Satellite (CTS) is a high-power broadcast satellite launched by NASA on January 17, 1976. CTS is the first satellite to operate at a frequency of 12 gigahertz and incorporates technology making possible new satellite telecommunications services. CTS is a cooperative program of the United States and Canada. This paper presents the results of the United States experimental activity to date. Wide segments of the population are involved in the Experiments Program, including the scientific community, other government agencies, industry, and the education and health entities. The experiments are associated with both technological objectives and the demonstration of new community and social services via satellite.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IAF PAPER 76-228 , International Astronautical Congress; Oct 10, 1976 - Oct 16, 1976; Anaheim, CA
    Format: text
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    NASA TECHNICAL REPORTS
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