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  • Other Sources  (199)
  • COMMUNICATIONS AND RADAR  (199)
  • 1980-1984  (199)
  • 1981  (199)
  • 1
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    Prediction techniques (1981)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: Prediction methods and related propagation results for the evaluation of Earth-space communication paths operating above 10 GHz are presented. Gaseous attenuation, rain, cloud, fog, sand, and dust attenuation, path diversity, signal fluctuations and low angle fading, depolarization effects, bandwidth coherence, and sky noise are considered.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Propagation Effects Handbook for Satellite Systems Design; p 195-348
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  • 2
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    Characteristics of rain and rain systems (1981)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: The description and measurement of the macroscopic and microscopic characteristics of rain and rain systems are discussed. The statistical relationships of these characteristics and their effect on polarization and attenuation are considered. Macroscopic characteristics include the size, distribution, and movements of rain cells, the height of melting layers, and the presence of ice crystals. Microscopic characteristics include the size distribution, density, and oblateness of rain drops and ice crystals. The estimation of a major propagation effect, specific attenuation, is described.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Propagation Effects Handbook for Satellite Systems Design; p 5-39
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  • 3
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    Propagation data bases (1981)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: Existing data bases accumulated as the result of experiments to gather propagation data on millimeter wave Earth-space links are described. The satellites used are described and results of the significant experiments conducted in the United States are summarized. The data bases consist primarily of cumulative attenuation statistics, though some depolarization measurements are included. Additional summaries of propagation data are cited.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Its Propagation Effects Handbook for Satellite Systems Design; p 155-194
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  • 4
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    An overview of several rain and attenuation models (1981)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: The key features of the Rice-Holmberg, Dutton-Dougherty, Global, Lin, and Piecewise Uniform Rain Rate models for estimation of cumulative attenuation statistics on Earth-space millimeter paths are summarized. The models provide either rain rate statistics or attenuation statistics, which can be related by use of the specific attenuation and the effective path length relation. The effective path length is defined. The advantages and disadvantages of each model for specific applications are discussed. The Global model is recommended as the design tool for predicting propagation effects in Earth-space communication systems.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Propagation Effects Handbook for Satellite Systems Design; p 41-101
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  • 5
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    Application of propagation predictions to Earth/space telecommunications system design (1981)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: The corresponding between a given propagation phenomenon and system performance is considered. Propagation data are related to system performance parameters, allowing the systems engineer to perform the analyses determining how well requirements are met by a given system design, and enabling the systems engineer to modify that design if necessary. The various ways of specifying performance criteria for different kinds of systems are discussed, and a general procedure for system design is presented and demonstrated.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Propagation Effects Handbook for Satellite Systems Design; p 349-404
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  • 6
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    Depolarization on Earth-space paths (1981)
    In:  CASI
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    Publication Date: 2006-02-14
    Description: Sources of depolarization effects on the propagation paths of orthogonally-polarized information channels are considered. The main sources of depolarization at millimeter wave frequencies are hydrometeor absorption and scattering in the troposphere. Terms are defined. Mathematical formulations for the effects of the propagation medium characteristics and antenna performance on signals in dual polarization Earth-space links are presented. Techniques for modeling rain and ice depolarization are discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Propagation Effects Handbook for Satellite Systems Design; p 103-154
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  • 7
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    Burst statistics of Viterbi decoding (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A mathematical model of Viterbi decoder burst error performance is presented. This model allows for computer generation of Viterbi-like error sequences quickly and inexpensively for applications where large amounts of data are required. The model is corroborated through comparisons with actual software decoder simulations.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Progr. Rept. 42-64; p 187-193
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  • 8
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    An efficient technique for the performance evaluation of antenna arrays with noisy carrier reference (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: An efficient computational technique is developed to evaluate the performance of coherent receivers with noisy carrier reference and multiple antennas. The received signal is assumed to be uncoded residual carrier BPSK (binary phase shift keying), with a PLL (phase locked loop) used for extracting the carrier. Explicit relationships between the error probabilities and the various system parameters are given. Specific results are given for the performance gain of combined carrier referencing over baseband only combining when the channel alignment process is ideal. A simple asymptotic expression for the performance gain is determined when the number of antennas used is increased without bound. An example using a Block 3 Deep Space Network PLL illustrates the performance of each arraying structure. The technique used is applicable to the performance evaluation for other receivers having similar decision statistics.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Progr. Rept. 42-64; p 194-206
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  • 9
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    The DSN VLBI system Mark 4-85 (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The DSN VLBI System was established as a network system in 1978. The evolution of the VLBI System from Mark 1-79 to Mark 4-85 is described, and the system functional requirements for Mark 4-85 are discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Progr. Rept. 42-64; p 61-76
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  • 10
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    DSN command system (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Modification of the currently operational DSN Command System MK 3-80 consisted of improvement of the uplink carrier frequency tuning capability to satisfy Voyager 2 requirements. Upgrading of Command System monitoring functions in the Network Operations Control Center is discussed. The DSN Command System requirements and functional design are described for the Mark 4 Network.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Progr. Rept. 42-64; p 53-60
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  • 11
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    Project ORION microwave subsystem design (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The proposed design for the microwave subsystem of Project ORION is presented. Performance characteristics and subsystem capabilities are discussed. Functional requirements and key performance parameters are stated for the subsystem as well as a proposed schedule of events.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Progr. Rept. 42-64; p 10-17
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  • 12
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    A multiple access communication network based on adaptive arrays (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A single frequency communication system is considered consisting of K possibly moving users distributed in space simultaneously communicating with a central station equipped with a computationally adapted array of n = or K antennas. Such a configuration could result if K spacecraft were to be simultaneously tracked by a single DSN complex consisting of an n antennas array. The array employs K sets of n weights to segregate the signals received from the K users. The weights are determined by direct computation based on known position information of the K users. Currently known techniques require (for n = K) about (4/3)K to the 4th power computer operations (multiply and add) to perform such computations. A technique that accomplishes this same goal in 8 K to the 3rd power operations, yielding a reduction by a factor K/6, was developed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 118-127
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  • 13
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    Atmospheric noise temperature measurements (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Radiometric microwave noise temperature measurements were used to estimate atmospheric transmission loss. The following lumped element model expression is used for the noise temperature contribution, T double prime = T sub p (1 - 1/L). This relationship is used to estimate the transmission loss L in terms of T double prime and the atmosphere effective physical temperature T sub p. This report evaluates T sub p in terms of assumed distributed loss and temperature models. Simplified expressions are presented for low loss applications. For these applications L was determined directly and accurately without integration or iteration.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 87-96
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  • 14
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    Effects of the gaseous and liquid water content of the atmosphere on range delay and Doppler frequency (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: When high precision is required for range measurement on Earth space paths, it is necessary to correct as accurately as possible for excess range delays due to the dry air, water vapor, and liquid water content of the atmosphere. Calculations based on representative values of atmospheric parameters are useful for illustrating the order of magnitude of the expected delays. Range delay, time delay, and phase delay are simply and directly related. Doppler frequency variations or noise are proportional to the time rate of change of excess range delay. Tropospheric effects were examined as part of an overall consideration of the capability of precision two way ranging and Doppler systems.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 71-86
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  • 15
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    The 34-meter antenna-subreflector translations to maximize RF gain (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The extension of the 26 meter antenna to 34 meter diameter decreased the F/D ratio. This F/D change resulted in unacceptable gain losses due to the hyperboloid's lateral deflections. A three direction translating mounting device was added to the hyperboloid. This device was controlled by a microprocessor to minimize the offsets of the phase centers in the cassegrain RF system and also compensated for boresight directions. The use of the radiation program to predict the gain losses from displacements computed by a structural computing program using an analytical model of the 34 meter reflector structure is discussed. Field test results showed accurate predictions for the Y and Z hyperboloid translations. In the X direction, the prediction value was low. However, the computed gain losses vs primary foci offsets by the radiation program were verified by field tests.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Telecommun. and Data Acquisition; p 112-120
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  • 16
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    Frequency standard test facility data acquisition and processing system (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The interim frequency standards test facility tests all frequency standards used in the DSN. It is also the central testing facility for testing all ultrastable hydrogen maser frequency standards. This proposed data acquisition/processing system was designed to support the IFSTF by acquiring and processing the large amounts of data generated there.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Telecommun. and Data Acquisition; p 22-30
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  • 17
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    Station stability measurement (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Methods and instrumentation are being developed to determine the frequency stability of Deep Space Stations. The efforts are presently focused on the verification of the stability of the X-band uplink and other RF and microwave subsystems which contribute to the overall stability of the system. The measurement methodology is presented as well as frequency stability data generated with the development measurement system. The system characteristics are highlighted and the potential areas where improvements could be made are discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Telecommun. and Data Acquisition; p 35-42
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  • 18
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    Fundamental limitations caused by RF propagation (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Propagation phenomena affect the design of radio frequency (RF) transmission systems. Propagation phenomena limit the suitability of portions of the frequency band for some applications, limit the reliability of RF transmission systems, and provide a means of coupling unwanted signals from one system to another with the potential of producing interference. The possibility of interference is the fundamental limitation to the unrestricted use of the frequency band. Phenomena affecting suitability, reliability, and the potential for interference are considered for frequencies in the 1- to 300-GHz range.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE; vol. 69
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  • 19
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    Narrow channel bandwidth receiver for VLBI (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: An introduction to the phase four receiver subsystem to be implemented into the DSN for VLBI applications is presented. The key design areas are discussed along with the design approach. Preliminary evaluation data indicate a feasible, straightforward design may be obtained.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Progr. Rept. 42-64; p 18-29
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  • 20
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    Capacity of a multimode direct detection optical communication channel (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The capacity is derived under both peak and average signal power constraints and without a signal bandwidth constraint. A random telegraph wave type signalling scheme of Kabanov is known to achieve capacity provided enough signalling bandwidth is available. In the absence of received background noise, an optimally coded PPM system is shown to achieve capacity with greatly reduced bandwidth as compared to Kabanov signals.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 51-70
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  • 21
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    New results on antenna arraying, part 1 (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Baseband combining with and without combined carrier referencing for antenna arrays are compared under two scenarios for the Voyager 2 Uranus encounter. The combined carrier reference scheme is estimated to outperform the baseband only scheme by less than 0.3 dB E (sub b)/N (sub 0) at a bit error probability of 0.005. These results were attained both with mathematical modeling and software Viterbi decoder simulations.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Telecommun. and Data Acquisition; p 105-111
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  • 22
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    ISPM X-band uplink technology demonstration. Part 1: Overview (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The ground and spacecraft hardware research, design, and implementation lead to an end to end in flight technology demonstration on the International Solar Polar Mission spacecraft. An introduction to the overall effort is given and the flight experiment objectives are established. The expected improvements in the telecommunications performance are summarized. Also presented is a conceptual mission operations plant.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Telecommun. and Data Acquisition; p 50-62
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  • 23
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    Tolerence and perturbation analysis (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Rectenna deviations are described which produce errors in the since of reduced efficiency and/or scattering. Three classes of deviations are emphasized: random construction variations; systematic variations; and atmospheric induced randomness.
    Keywords: COMMUNICATIONS AND RADAR
    Type: A Theoret. Study of Microwave Beam Absorption by a Rectenna; p 93-107
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  • 24
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    Grating lobes (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The radiation patterns characteristic of an indefinite planar array of isotropic antennas was investigated. Particular emphasis was given to the grating lobe scatter from the rectenna. It is shown that an idealy arrayed rectenna of indefinite extent would produce grating lobes which are impulsive. It is further shown that a shift to finite extent or introduction of typical variations in element placement should generate more typical patterns.
    Keywords: COMMUNICATIONS AND RADAR
    Type: A Theoret. Study of Microwave Beam Absorption by a Rectenna; p 81-90
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  • 25
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    Waveguide model (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A model is presented which quantifies the electromagnetic modes (field configurations) in the immediate vicinity of the rectenna element. Specifically, the waveguide model characterizes the electromagnetic modes generated by planar waves normal to the array. The model applies only to incidence normal to the array.
    Keywords: COMMUNICATIONS AND RADAR
    Type: A Theoret. Study of Microwave Beam Absorption by a Rectenna; p 59-77
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  • 26
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    A theoretical study of microwave beam absorption by a rectenna, introduction (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The conditions required for a large rectenna array (i.e., reference design) to absorb nearly 100% of transmitted energy were studied. Design parameters including element spacing, and the manner in which these affect scatter were formulated. Amplitudes and directions of scatter and development of strategies for mitigation were also investigated. The effects on rectenna behavior of external factors such as weather and aircraft overflights were determined.
    Keywords: COMMUNICATIONS AND RADAR
    Type: A Theoret. Study of Microwave Beam Absorption by a Rectenna; p 1-36
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  • 27
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    Coherent detection of frequency-hopped quadrature modulations in the presence of jamming. II - QPR Class I modulation (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: This paper considers the performance of quadrature partial response (QPR) in the presence of jamming. Although a QPR system employs a single sample detector in its receiver, while quadrature amplitude shift keying (or quadrature phase shift keying) requires a matched-filter type of receiver, it is shown that the coherent detection performances of the two in the presence of the intentional jammer have definite similarities.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Communications; COM-29; Nov. 198
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  • 28
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    Antenna beam solid angle relationships (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Some of the useful formulas and methods for determining antenna beam solid angle are presented. The applicability of these formulas in evaluating radiometric systems performance is illustrated.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Progr. Rept. 42-64; p 168-172
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  • 29
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    Boresighting techniques for the Antenna Control Assembly (ACA) (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Comparison of four scanning schemes including CONSCAN indicates that CONSCAN with signal cleanup and protection processes has the greatest merit in terms of accuracy, dependability and automatic unattended operation. Specific problem areas, error sources, and corrective measures are discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Progr. Rept. 42-64; p 116-122
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  • 30
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    Radio frequency interference protection of communications between the Deep Space Network and deep space flight projects (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The increasing density of electrical and electronic circuits in Deep Space Station systems for computation, control, and numerous related functions has combined with the extension of system performance requirements calling for higher speed circuitry along with broader bandwidths. This has progressively increased the number of potential sources of radio frequency interference inside the stations. Also, the extension of spectrum usage both in power and frequency as well as the greater density of usage at all frequencies for national and international satellite communications, space research, Earth resource operations and defense, and particularly the huge expansion of airborne electronic warfare and electronic countermeasures operations in the Mojave area have greatly increased the potential number and severity of radio frequency interference incidents. The various facets of this problem and the efforts to eliminate or minimize the impact of interference on Deep Space Network support of deep space flight projects are described.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Telecommun. and Data Acquisition; p 125-131
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  • 31
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    Tropospheric/ionospheric transmission tests (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Four tests are described which are designed to evaluate the magnitude, type, and frequency of occurence of amplitude and phase variations in the solar power satellite power (SPS) beam as seen by the rectenna. Particular attention is given to the degree of deviation in the propagation observed under two conditions unique to the SPS: monochromaticity; and smallness of the effective aperture of individual rectenna element dipoles.
    Keywords: COMMUNICATIONS AND RADAR
    Type: A Theoret. Study of Microwave Beam Absorption by a Rectenna; p 111-118
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  • 32
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    Current sheet model (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The model of a rectenna based on the current sheet equivalency of a large planar array is described. The model is mathematically characterized by expression for the fraction of the incident plane wave that is reflected from the sheet. The model is conceptually justified for normal incidence by comparing it to the waveguide model in which evanescent modes, present as beyond and cutoff, correspond to the near field components which become negligible at any significant distance from the antenna array.
    Keywords: COMMUNICATIONS AND RADAR
    Type: A Theoret. Study of Microwave Beam Absorption by a Rectenna; p 47-56
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  • 33
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    Plane wave derivation (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The characteristic of plane waves are derived from Maxwell's equations. The derivation utilizes both the transmission and reflection of plane waves as a basis for its formulation.
    Keywords: COMMUNICATIONS AND RADAR
    Type: A Theoret. Study of Microwave Beam Absorption by a Rectenna; p 39-43
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  • 34
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    Conversion of the DSN teletype subsystem to the eight-level ASCII national standard (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A functional description of the new eight level ASCII Teletype Subsystem and its constitutent Teletype Assemblies is given. An overview of the implementation of the Teletype Subsystem is presented together with a discussion of the distinct capabilities of its equipment.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition; p 95-102
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  • 35
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    Command system output bit verification (1981)
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    Publication Date: 2011-08-18
    Description: An automatic test was developed to test the ability of the deep space station (DSS) command subsystem and exciter to generate and radiate, from the exciter, the correct idle bit sequence for a given flight project or to store and radiate received command data elements and files without alteration. This test, called the command system output bit verification test, is an extension of the command system performance test (SPT) and can be selected as an SPT option. The test compares the bit stream radiated from the DSS exciter with reference sequences generated by the SPT software program. The command subsystem and exciter are verified when the bit stream and reference sequences are identical. It is a key element of the acceptance testing conducted on the command processor assembly (CPA) operational program (DMC-0584-OP-G) prior to its transfer from development to operations.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition; p 112-114
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  • 36
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    Historical data on characteristics of radio systems used for United States deep-space communications (1981)
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    Publication Date: 2011-08-18
    Description: Historical data on selected communication parameters are presented in tables and charts for 14 deep space missions. Some observations are made about trends in communication capability.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition; p 7-16
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  • 37
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    Two-channel Costas loop tracking performance for UQPSK signals with arbitrary data formats (1981)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Previous results on the tracking performance of two-channel Costas-type carrier synchronization loops are generalized and corrected, in order that they may be applied to several mixed-format cases. In particular, the mean-square phase jitter performance of these loops with active arm filters, synchronous or asynchronous symbol clocks, and arbitrary data formats on the two channels is examined. It is demonstrated that for each case, selection of the channel gain ratio, as motivated by the MAP estimation theory, does not guarantee optimum loop tracking performance: in some instances, a conventional single-channel Costas loop would outperform the two-channel version with the MAP choice of gain ratio. It is suggested that the gain ratio be chosen to directly minimize the mean-square phase tracking jitter which is equivalent to minimizing the loop's 'squaring loss'. This can, in some cases, improve the performance measure, although in all cases, the two-channel loop will still outperform the single-channel version.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Communications; COM-29; Sept
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    Investigation of a solid state power combining antenna proposed for use in the solar power satellite (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Performance tests performed on a four-feed microstrip antenna and feed network are analyzed. Frequency response with and without amplifiers, an investigation of noise threshold, phase tracking, and jitter are included. Recommendations for further development of SPS power conversion modules are also included.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The 1981 NASA ASEE Summer Fac. Fellowship Program, Vol. 1; 28 p
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  • 39
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    Effects of rain and fog on the Shuttle Ku-band microwave scanning beam landing system range and accuracy performance (1981)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The microwave Scanning Beam Landing System's (MSBLS) performance in fog and rain was studied. The fog and rain effects on the Shuttle Ku-band system were determined. Specifically, microwave attenuation, beam distortion, and coordinate errors resulting from operation of the MSBLS in poor weather conditions were evaluated. The main physical processes giving rise to microwave attenuation were found to be absorption and scattering by water droplets. The general theory of scattering and absorption used is discussed and a listing of applicable computer programs is provided.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The 1981 NASA ASEE Summer Fac. Fellowship Program, Vol. 1; 33 p
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  • 40
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    Coherent detection of frequency-hopped quadrature modulations in the presence of jamming. I - QPSK and QASK modulations (1981)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: This paper examines the performance of coherent QPSK and QASK systems combined with FH or FH/PN spread spectrum techniques in the presence of partial-band multitone or noise jamming. The worst-case jammer and worst-case performance are determined as functions of the signal-to-background noise ratio (SNR) and signal-to-jammer power ratio (SJR). Asymptotic results for high SNR are shown to have a linear dependence between the jammer's optimal power allocation and the system error probability performance.
    Keywords: COMMUNICATIONS AND RADAR
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  • 41
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    The SA-2239/WLQ-4(V) Cutty Sark distribution system (1981)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A redundant frequency and time distribution system provides a multiplicity of isolated outputs, all of which are derived from three atomic frequency standards. The distribution system monitors input parameters of the signals coming from the Cesium Standards and selects one to be the primary standard, phase locks an internal oscillator which has excellent aging characteristics in the open loop mode and acts as a filter to provide phase noise improvement, and generates 1 megahertz and 100 kHz by direct synthesis. Additionally, the system distributes RF and timing signals consisting of 5 MHz, 1 MHz, 100 kHz, BCD Time-of-Day, 1 pps and 1 ppm.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA. Goddard Space Flight Center Proc. of the 12th Ann. Precise Time and Time Interval. and Planning; p 765-783
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  • 42
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    Some new results on the frequency characteristics on quartz crystals irradiated by ionizing and particle radiations (1981)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The frequency behavior of AT-cut quartz crystals irradiated by X -, gamma rays and fast neutrons. Initial instability in frequency for gamma and neutron irradiated crystals was found. All the different radiations first give a negative frequency shift at lower doses which are followed by positive frequency shift for increased doses. Results are explained in terms of the fundamental crystal structure. Applications of the frequency results for radiation hardening are proposed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA. Goddard Space Flight Center Proc. of the 12th Ann. Precise Time and Time Interval Appl. and Planning Meeting; p 829-849
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  • 43
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    The NATO III 5 MHz Distribution System (1981)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A high performance 5 MHz distribution system is described which has extremely low phase noise and jitter characteristics and provides multiple buffered outputs. The system is completely redundant with automatic switchover and is self-testing. Since the 5 MHz reference signals distributed by the NATO III distribution system are used for up-conversion and multiplicative functions, a high degree of phase stability and isolation between outputs is necessary. Unique circuit design and packaging concepts insure that the isolation between outputs is sufficient to quarantee a phase perturbation of less than 0.0016 deg when other outputs are open circuited, short circuited or terminated in 50 ohms. Circuit design techniques include high isolation cascode amplifiers. Negative feedback stabilizes system gain and minimizes circuit phase noise contributions. Balanced lines, in lieu of single ended coaxial transmission media, minimize pickup.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA. Goddard Space Flight Center Proc. of the 12th Ann. Precise Time and Time Interval Appl. and Planning Meeting; p 743-764
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  • 44
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    Source structure errors in radio-interferometric clock synchronization for ten measured distributions (1981)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The effects of source structure on radio interferometry measurements were investigated. The brightness distribution measurements for ten extragalactic sources were analyzed. Significant results are reported.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA. Goddard Space Flight Center Proc. of the 12th Ann. Precise Time and Time Interval Appl. and Planning Meeting; p 635-645
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  • 45
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    Carrier tracking loop performance in the presence of strong CW interference (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The analyses of Bruno (1973) and Blanchard (1974, 1975) of the effects of strong radio-frequency interference on the behavior of a phase-locked loop are examined in detail. The lock constraints derived directly from a steady-state trial solution by Bruno and those derived with simplifying assumptions from the same trial solution by Blanchard are compared, and circumstances which may be accommodated by the results of Bruno but not those of Blanchard are pointed out. An explicit approximation is then derived which extends the closed-form approximation of Bruno for the loop phase error to the entire lock region. Results are illustrated for a loop filter representative of a phase-locked loop in a deep space network receiver.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Communications; COM-29; June 198
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  • 46
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    Estimation of the propagation delay through the troposphere from microwave radiometer data (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Microwave propagation delay through the troposphere is studied as a means of estimating the adverse effect of atmospheric water vapor on the accuracy of measurements made with very long baseline interferometry. Vertical profiles of temperature and water vapor density were obtained from a total of 240 radiosonde launches taken simultaneously at three New England locations in 1974; all studies were made at the 19 and 22.2 GHz frequency operating range of the radiometers. The wet path length in the zenith direction could be estimated from the surface water vapor density to an accuracy of 5 cm for the summer data and 2 cm for winter data, and with the brightness temperatures, it could be estimated to an accuracy of 0.3 cm. Two dual-frequency radiometers were also used to determine the accuracy of prediction of the path length from real radiometry data. The rms error for the estimation of wet path length from surface meteorological parameters was 3.2 cm, and for the radiometer brightness temperatures the rms error was 1.5 cm.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Radio Science; 16; Mar
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  • 47
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    Power spectra of multi-h phase codes (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: A procedure is presented for calculating the power spectrum of the class of digital continuous-phase signals known as multi-h phase codes. These signals have been shown to have attractive power advantages over other uncoded digital schemes such as QPSK, and represent a bandwidth-efficient alternative to other coding techniques. The method is general, handling M-ary signaling, various frequency pulse shapes, and arbitrary sets of modulation indices. Numerical results are shown for several specific codes. In addition, the issue of spectral lines is resolved, and simple spectral approximations are developed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Communications; COM-29; Mar. 198
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  • 48
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    Spatial and temporal filtering technique for processing lidar photocount data (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Shot noise places a practical limit on the spatial and temporal resolution of lidar photocount data. A 2-D signal-processing technique that utilizes spatial and temporal filtering to reduce shot noise and increase resolution is described. The technique is applied to sodium lidar data collected during the fall of 1979 over Urbana, Illinois. Temporal filtering is shown to enhance the spatial resolution of the sodium profiles significantly by reducing shot noise by more than 10 dB. The signal-processing technique is applicable to a wide variety of lidar data.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Optics Letters; 6; Apr. 198
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    Antennas in matter: Fundamentals, theory, and applications (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The volume provides an introduction to antennas and probes embedded within or near material bodies such as the earth, the ocean, or a living organism. After a fundamental analysis of insulated and bare antennas, an advanced treatment of antennas in various media is presented, including a detailed study of the electromagnetic equations in homogeneous isotropic media, the complete theory of the bare dipole in a general medium, and a rigorous analysis of the insulated antenna as well as bare and insulated loop antennas. Finally, experimental models and measuring techniques related to antennas and probes in a general dissipative or dielectric medium are examined.
    Keywords: COMMUNICATIONS AND RADAR
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    On-board processing for future satellite communications systems: Satellite-Routed FDMA (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A frequency division multiple access (FDMA) 30/20 GHz satellite communications architecture without on-board baseband processing is investigated. Conceptual system designs are suggested for domestic traffic models totaling 4 Gb/s of customer premises service (CPS) traffic and 6 Gb/s of trunking traffic. Emphasis is given to the CPS portion of the system which includes thousands of earth terminals with digital traffic ranging from a single 64 kb/s voice channel to hundreds of channels of voice, data, and video with an aggregate data rate of 33 Mb/s. A unique regional design concept that effectively smooths the non-uniform traffic distribution and greatly simplifies the satellite design is employed. The satellite antenna system forms thirty-two 0.33 deg beam on both the uplinks and the downlinks in one design. In another design matched to a traffic model with more dispersed users, there are twenty-four 0.33 deg beams and twenty-one 0.7 deg beams. Detailed system design techniques show that a single satellite producing approximately 5 kW of dc power is capable of handling at least 75% of the postulated traffic. A detailed cost model of the ground segment and estimated system costs based on current information from manufacturers are presented.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-165419 , NASA/LERC-C-49029-D , MTR-8311
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    The effects of receiver tracking phase error on the performance of the concatenated Reed-Solomon/Viterbi channel coding system (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Analytical and experimental results are presented of the effects of receiver tracking phase error, caused by weak signal conditions on either the uplink or the downlink or both, on the performance of the concatenated Reed-Solomon (RS) Viterbi channel coding system. The test results were obtained under an emulated S band uplink and X band downlink, two way space communication channel in the telecommunication development laboratory of JPL with data rates ranging from 4 kHz to 20 kHz. It is shown that, with ideal interleaving, the concatenated RS/Viterbi coding system is capable of yielding large coding gains at very low bit error probabilities over the Viterbi decoded convolutional only coding system. Results on the effects of receiver tracking phase errors on the performance of the concatenated coding system with antenna array combining are included.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-164857 , JPL-PUB-81-62
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    Frequency and timing system for the consolidated DSN and STDN tracking network (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The consolidation on the existing Deep Space Network (DSN) and colocated Goddard Spaceflight Tracking and Data Network (STDN) stations into a multiple antenna array is discussed. Each site includes a signal processing center (SPC) centered in an array of four or five antennas each located within approximately 300 to 800 meters of the SPC. A central frequency and timing system (FTS) located in the SPC contains reference frequency, timing and time code generation, and distribution equipment for both the SPC and each antenna with its associated front end antenna control building. The reference frequency distribution and clock equipment are driven by a hydrogen maser as the prime frequency standard with cesium beam frequency standard as the secondary.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA. Goddard Space Flight Center Proc. of the 12th Ann. Precise Time and Time Interval Appl. and Planning Meeting; p 591-614
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    Radio frequency interference at the geostationary orbit (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Growing demands on the frequency spectrum have increased the possibility of radio frequency interference (RFI). Various approaches to obtain in orbit RFI data are compared; this comparision indicates that the most practical way to obtain RFI data for a desired orbit (such as a geostationary orbit) is through the extrapolation of in orbit RFI measurements by a low orbit satellite. It is concluded that a coherent RFI program that uses both experimental data and analytical predictions provides accurate RFI data at minimal cost.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-164531 , JPL-PUB-81-34
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    Apparatus and method for determining the position of a radiant energy source (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The position of a terrestrial RF source is determined from a geostationary, synchronous satellite by scanning the beam of a narrow beam width antenna in first and second orthogonal directions over a region including the source. The peak level of energy transduced by the antenna in each of the scanning directions is detected and correlated with the scanning position of the beam by feeding the output of a detector responsive to the transduced signal to an indicator of an X-Y recorder. The X and Y axes of the recorder are scanned in synchronism with the beam being respectively scanned in the first and second directions to form X and Y traces on which are indicated the detected peak position in each of the scanning directions. The source position is determined from an intersection of lines drawn parallel to the X and Y axes and including the detected peak position of each trace.
    Keywords: COMMUNICATIONS AND RADAR
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    A Theoretical Study of Microwave Beam Absorption by a Rectenna (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The theoretical operational parameters for the workable satellite power system were examined. The system requirements for efficient transmission and reception of an environmentally benign microwave beam were determined.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-160921
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    Optical data transmission technology for fixed and drag-on STS payload umbilicals, volume 2 (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Optical data handling methods are studied as applicable to payload communications checkout and monitoring. Both payload umbilicals and interconnecting communication lines carrying payload data are examined for the following: (1) ground checkout requirements; (2) optical approach (technical survey of optical approaches, selection of optimum approach); (3) survey and select components; (4) compare with conventional approach; and (5) definition of follow on activity.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-166825-VOL-2
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    Optical data transmission technology for fixed and drag-on STS payloads umbilicals. Volume 1: Executive summary (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The feasibility of using optical data handling methods to transmit payload checkout and telemetry is discussed. Optical communications are superior to conventional communication systems for the following reasons: high data capacity optical channels; small and light weight optical cables; and optical signal immunity to electromagnetic interference. Task number one analyzed the ground checkout data requirements that may be expected from the payload community. Task number two selected the optical approach based on the interface requirements, the location of the interface, the amount of time required to reconfigure hardware, and the method of transporting the optical signal. Task number three surveyed and selected optical components for the two payload data link. Task number four makes a qualitative comparison of the conventional electrical communication system and the proposed optical communication system.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-166825-VOL-1
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    Synthetic aperture radar and digital processing: An introduction (1981)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: A tutorial on synthetic aperture radar (SAR) is presented with emphasis on digital data collection and processing. Background information on waveform frequency and phase notation, mixing, Q conversion, sampling and cross correlation operations is included for clarity. The fate of a SAR signal from transmission to processed image is traced in detail, using the model of a single bright point target against a dark background. Some of the principal problems connected with SAR processing are also discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-163985 , JPL-PUB-80-90
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    Asynchronous multiple-access channel capacity (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The capacity region for the discrete memoryless multiple-access channel without time synchronization at the transmitters and receivers is shown to be the same as the known capacity region for the ordinary multiple-access channel. The proof utilizes time sharing of two optimal codes for the ordinary multiple-access channel and uses maximum likelihood decoding over shifts of the hypothesized transmitter words.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Information Theory; IT-27; July 198
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    RFI simulation definition study, exhibit D (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Comparative analyses of experimental and predicted effects of the radio frequency interference (RFI) environment on the Shuttle/TDRSS S-band links were performed. Specifications are defined ad ESTL test requirements are presented. Procedures for using the RFI test generator in the ESTL S-band link tests are presented and performance predictions for these links in the RFI environment are provided.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-161083 , TR-0982(1179-200)
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    MLS antenna locations for the deHaviland DASH 7 aircraft (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Several proposed aircraft antenna locations were investigated to determine their potential for satisfying the microwave landing system antenna coverage requirements. The results of this investigation are presented and antenna locations are recommended for the deHavilland DASH 7 aircraft.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-83195
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    Microwave noise temperature and attenuation of clouds at frequencies below 50 GHz (1981)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: The microwave attenuation and noise temperature effects of clouds can result in serious degradation of telecommunications link performance, especially for low-noise systems presently used in deep-space communications. Although cloud effects are generally less than rain effects, the frequent presence of clouds will cause some amount of link degradation a large portion of the time. Cloud types, water particle densities, radiative transfer, attenuation and noise temperature calculations are reviewed and examples of basic link signal to noise ratio calculations are given. Calculations for twelve different cloud models are presented for frequencies of from 1 to 50 GHz and elevation angles of 30 degrees and 90 degrees. These case results may be used as a handbook to predict noise temperature and attenuation values for known or forecast cloud conditions.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-164702 , JPL-PUB-81-46
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    Scattering of Pruppacher-Pitter raindrops at 30 GHz (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Optimum design of modern ground-satellite communication systems requires the knowledge of rain-induced differential attenuation, differential phase shift, and cross polarization factors. Different available analytical techniques for raindrop scattering problems were assessed. These include: (1) geometrical theory of diffraction; (2) method of moment; (3) perturbation method; (4) point matching methods; (5) extended boundary condition method; and (6) global-local finite element method. The advantages and disadvantages of each are listed. The extended boundary condition method, which was determined to yield the most scattering results, is summarized. The scattered fields for Pruppacher-Pitter raindrops with sizes ranging from 0.5 mm to 3.5 mm at 20 C and at 30 GHz for several incidence angles are tabulated.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-164699 , JPL-PUB-81-63
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    An experimental study of the concatenated Reed-Solomon/Viterbi channel coding system performance and its impact on space communications (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The need for efficient space communication at very low bit error probabilities to the specification and implementation of a concatenated coding system using an interleaved Reed-Solomon code as the outer code and a Viterbi-decoded convolutional code as the inner code. Experimental results of this channel coding system are presented under an emulated S-band uplink and X-band downlink two-way space communication channel, where both uplink and downlink have strong carrier power. This work was performed under the NASA End-to-End Data Systems program at JPL. Test results verify that at a bit error probability of 10 to the -6 power or less, this concatenated coding system does provide a coding gain of 2.5 dB or more over the Viterbi-decoded convolutional-only coding system. These tests also show that a desirable interleaving depth for the Reed-Solomon outer code is 8 or more. The impact of this "virtually" error-free space communication link on the transmission of images is discussed and examples of simulation results are given.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-164698 , JPL-PUB-81-58
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    Radar altimeter waveform modeled parameter recovery (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Satellite-borne radar altimeters include waveform sampling gates providing point samples of the transmitted radar pulse after its scattering from the ocean's surface. Averages of the waveform sampler data can be fitted by varying parameters in a model mean return waveform. The theoretical waveform model used is described as well as a general iterative nonlinear least squares procedures used to obtain estimates of parameters characterizing the modeled waveform for SEASAT-1 data. The six waveform parameters recovered by the fitting procedure are: (1) amplitude; (2) time origin, or track point; (3) ocean surface rms roughness; (4) noise baseline; (5) ocean surface skewness; and (6) altitude or off-nadir angle. Additional practical processing considerations are addressed and FORTRAN source listing for subroutines used in the waveform fitting are included. While the description is for the Seasat-1 altimeter waveform data analysis, the work can easily be generalized and extended to other radar altimeter systems.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-73294
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    Doppler-cancelled response to VLF gravitational waves (1981)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: The interaction of long periodic gravitational waves with a three link microwave system known as the Doppler Cancelling System is discussed. This system, which was developed for a gravitational redshift experiment, uses one-way and two-way Doppler informatin to construct the beat signal of two reference oscillators moving with respect to each other. The geometric optics approximation is used to derive the frequency shift produced on a light signal propagating in a gravitational wave space-time. The signature left on the Doppler-cancelled beat by burst and continuous gravitational waves is analyzed. A comparison is made between the response to gravitational waves of the Doppler Cancelling System and that of a Doppler tracking system which employs two-way, round-trip radio waves. A three-fold repetition of the gravitational wave form is found to be a common feature of the response functions of both systems. These two functions otherwise exhibit interesting differences.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-82434
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    Baseband signal combiner for large aperture antenna array (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The invention provides a means whereby the baseband output signals of all but one of the receivers associated with each of the antennas are summed and used as a correlation reference for the baseband signal not contained in the summed signal, thereby providing a plurality of correlation or alignment loops, each having an output signal related to the phase difference between its input baseband signal and the summed signal. The invention further provides a means for subtracting an output or error signal generated in one of the correlation loops whose baseband signal has a predetermined phase delay from all the other alignment loops, thereby avoiding interaction and reflection effects in the signal combiner. A variable phase delay means for each of the other baseband signals is controlled by its corresponding correlation loop.
    Keywords: COMMUNICATIONS AND RADAR
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    A microcomputer based data acquisition system and experiment controller (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A data acquisition system is described. The system monitors and records the signal strength of a radio beacon sent to Earth from a geosynchronous satellite. It acquires data from several devices such as a radar, a radiometer, and a rain gauge which monitor the meteorological conditions along the Earth space propagation path. The acquired data are stored in digital format on magnetic tape for analysis at the computer center. A detailed description of the design and operation of the system's various hardware components is given. Schematic diagrams, the theory of operation, and normal operating procedures are presented.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-164535 , TR-712759-3 , ESL-712759-3
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  • 69
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    Amplitude and angle of arrival measurements on a 28.56 GHz Earth-space path (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The amplitude and angle of arrival measurements on an Earth-space path using the 28.56 GHz COMSTAR D3 satellite beacon are described. These measurements were made by the Ohio State University ElectroScience Laboratory during the period September 1978 to September 1979. Monthly, quarterly, and annual distributions of attenuation, angle of arrival, and variance of both these parameters are reported. During this period, fades exceeding 29 dB for .00% of the time and angle of arrival fluctuations exceeding .12 degrees for .01% of the time were observed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-164533 , ESL-TR-712759-4
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    The Deep Space Network: An instrument for radio science research (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Doppler and ranging data routinely generated at the Deep Space Stations of the California Institute of Technology-Jet Propulsion Laboratory Deep Space Network serve as an excellent source of radio science information. Important radio science experiments based on Deep Space Network generated radio metric data have included confirmation of Einstein's Theory of Relativity, measurement of the masses and gravitational harmonics of the planets out to Saturn, and measurement of electron density distribution and turbulence in the solar corona. In response to an increased level of radio science requirements, the Deep Space Network chose in 1976 to implement a new radio science system, which was completed in late 1978. Key features include (1) highly phase stable open loop receivers, (2) reduction of recorded data bandwidth through use of programmed local oscillators, and (3) real time digitization and recording on computer compatible tape.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-164077 , JPL-PUB-80-93
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  • 71
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    On the power spectral density of quadrature modulated signals (1981)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: The conventional (no-offset) quadriphase modulation technique suffers from the fact that hardlimiting will restore the frequency sidelobes removed by proper filtering. Thus, offset keyed quadriphase modulation techniques are often proposed for satellite communication with bandpass hardlimiting. A unified theory is developed which is capable of describing the power spectral density before and after the hardlimiting process. Using the in-phase and the quadrature phase channel with arbitrary pulse shaping, analytical results are established for generalized quadriphase modulation. In particular MSK, OPSK or the recently introduced overlapped raised cosine keying all fall into this general category. It is shown that for a linear communication channel, the power spectral density of the modulated signal remains unchanged regardless of the offset delay. Furthermore, if the in phase and the quadrature phase channel have identical pulse shapes without offset, the spectrum after bandpass hardlimiting will be identical to that of the conventional QPSK modulation. Numerical examples are given for various modulation techniques. A case of different pulse shapes in the in phase and the quadrature phase channel is also considered.
    Keywords: COMMUNICATIONS AND RADAR
    Type: JPL-PUB-80-95
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  • 72
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    Alternative licensing arrangements and spectrum economics: The case of multipoint distribution service (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: At present, the Federal Communications Commission assigns radio licenses following a determination of the public interest. Whenever mutually conflicting license applications are filed, the Commission holds a comparative hearing. This assignment mechanism is criticized as cumbersome and unrealiable, and three alternatives are proposed: increasing the available spectrum, and either auctions or lotteries of radio licenses. An analysis is presented of the present system and these alternative arrangments for assigning rights to the frequency spectrum for the Multipoint Distribution Service (MDS). Although MDS is a relatively minor radio service, it serves as a prototype for message distribution services with a large potential for use in business communications. Moreover, the way in which the initial batch of MDS licenses was assigned provides a unique opportunity for empirical work on the economics of the licensing process.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-163922 , SU-31
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  • 73
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    A modified adaptive delta modulator (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: This paper presents the results of a study in data compression of adaptive delta modulated video signals. The Song mode ADM is first investigated at a sampling rate of 16 Mbits/s and shown not to produce enough redundancy to warrant entropy encoding. A modified adaptive delta modulator algorithm is presented that operates at a sampling rate of 16 Mbits/s and does produce sufficient redundancy to yield a 40-50 percent data compression by using a simple code on 4 bit data blocks. Other techniques such as field interpolation and direct substitution are shown to increase the possible data compression further without noticeable degradation in the two input images used in this investigation. The effects of channel errors in the transmission of packet video over a computer network are considered. A leaky integrator is used to reduce the effects of channel errors in the data bits. It is shown that the effects of channel errors can be reduced by field interpolating those packets that can be shown to contain errors.
    Keywords: COMMUNICATIONS AND RADAR
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  • 74
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    VLF Radio Field Strength Measurement of power line carrier system in San Diego, California (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The radio frequency interference (RFI) potential was evaluated for a Powerline Carriet (PLC) installed in San Diego which monitors the performance of an electrical power system. The PLC system generated 30 amperes at 5.79 kHz. The RF radiations were measured to be (typically) 120 dBuV/m at the beginning of the 12 kV powerline and 60 dBuV/m at the end of the powerline. The RF fields varied inversely as the distance squared. Measurements were also performed with a 45 kHz PLC system. The RF fields were of similar amplitude.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-169244 , NAS 1.26:169244 , JPL-9950-689 , EMACO-8101-10
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  • 75
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    System data communication structures for active-control transport aircraft, volume 1 (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Candidate data communication techniques are identified, including dedicated links, local buses, broadcast buses, multiplex buses, and mesh networks. The design methodology for mesh networks is then discussed, including network topology and node architecture. Several concepts of power distribution are reviewed, including current limiting and mesh networks for power. The technology issues of packaging, transmission media, and lightning are addressed, and, finally, the analysis tools developed to aid in the communication design process are described. There are special tools to analyze the reliability and connectivity of networks and more general reliability analysis tools for all types of systems.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-165773 , NAS 1.26:165773 , R-1469-VOL-1
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    System data communication structures for active-control transport aircraft, volume 2 (1981)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: The application of communication structures to advanced transport aircraft are addressed. First, a set of avionic functional requirements is established, and a baseline set of avionics equipment is defined that will meet the requirements. Three alternative configurations for this equipment are then identified that represent the evolution toward more dispersed systems. Candidate communication structures are proposed for each system configuration, and these are compared using trade off analyses; these analyses emphasize reliability but also address complexity. Multiplex buses are recognized as the likely near term choice with mesh networks being desirable for advanced, highly dispersed systems.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-165774 , NAS 1.26:165774 , R-1469-VOL-2
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  • 77
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    A Simulation System for Validating the Analytical Prediction of Performance of the Convolutional Encoded and Symbol Interleaved TDRSS S-band Return Link Service in a Pulsed RFI Environment (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A hardware integrated convolutional coding/symbol interleaving and integrated symbol deinterleaving/Viterbi decoding simulation system is described. Validation on the system of the performance of the TDRSS S-band return link with BPSK modulation, operating in a pulsed RFI environment is included. The system consists of three components, the Fast Linkabit Error Rate Tester (FLERT), the Transition Probability Generator (TPG), and a modified LV7017B which includes rate 1/3 capability as well as a periodic interleaver/deinterleaver. Operating and maintenance manuals for each of these units are included.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-170428 , NAS 1.26:170428
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  • 78
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    An improved empirical model for diversity gain on Earth-space propagation paths (1981)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: An empirical model was generated to estimate diversity gain on Earth-space propagation paths as a function of Earth terminal separation distance, link frequency, elevation angle, and angle between the baseline and the path azimuth. The resulting model reproduces the entire experimental data set with an RMS error of 0.73 dB.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-169039 , NAS 1.26:169039 , ESL-713656-1 , JPL-9950-664
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  • 79
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    Mean dyadic Green's function for a two layer random medium (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The mean dyadic Green's function for a two-layer random medium with arbitrary three-dimensional correlation functions has been obtained with the zeroth-order solution to the Dyson equation by applying the nonlinear approximation. The propagation of the coherent wave in the random medium is similar to that in an anisotropic medium with different propagation constants for the characteristic transverse electric and transverse magnetic polarizations. In the limit of a laminar structure, two propagation constants for each polarization are found to exist.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Radio Science; 16; Nov
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  • 80
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    A new look at Fresnel field computation using the Jacobi-Bessel series (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Computational procedures that would be useful in finding the Fresnel field from a knowledge of the Jacobi-Bessel expansion of the far field are considered. The range of validity of the Fresnel approximation is carefully examined by comparing it with the exact closed form solution for the uniform circular aperture. Also investigated numerically, and in great detail, is the range of validity (over theta) of the Fresnel small angle (FSA) approximation. For moderate sized apertures as small as 10 wavelengths, it is found that the FSA approximation is very accurate to angles as wide as four or more sidelobes (as seen in the far zone). A very efficient computational method is shown to exist for the radiation integral in the form of a single series expansion that is analytically continuous and convergent for a wide range of observation points in three-dimensional space.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation; AP-29; Nov. 198
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    A review of transhorizon propagation phenomena (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Interference problems underlie the current interest in transhorizon propagation. In particular, statistics of the rare, high-level fields are of interest. This paper reviews the propagation mechanisms which produce the high-level fields and summarizes recent work in the modeling of the transhorizon propagation.
    Keywords: COMMUNICATIONS AND RADAR
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    Shuttle STS-2 mission communication systems RF coverage and performance predictions. Volume 1: Ascent (1981)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: The RF communications capabilities and nominally expected performance for the ascent phase of the second orbital flight of the shuttle are provided. Predicted performance is given mainly in the form of plots of signal strength versus elapsed mission time for the STDN (downlink) and shuttle orbiter (uplink) receivers for the S-band PM and FM, and UHF systems. Performance of the NAV and landing RF systems is treated for RTLS abort, since in this case the spacecraft will loop around and return to the launch site. NAV and landing RF systems include TACAN, MSBLS, and C-band altimeter. Signal strength plots were produced by a computer program which combines the spacecraft trajectory, antenna patterns, transmit and receive performance characteristics, and system mathematical models. When available, measured spacecraft parameters were used in the predictions; otherwise, specified values were used. Specified ground station parameter values were also used. Thresholds and other criteria on the graphs are explained.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-84853 , JSC-17625-VOL-1 , NAS 1.15:84853
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  • 83
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    Integrated command, control communication and computation system study (1981)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: The study was conducted in three phases: a functional requirements phase; a functional architecture phase; and a design plan phase. The major emphasis was on the functional architecture phase and the approaches used for its functional hierarchy, operations concept, and interfaces.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-166738
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    Integrated command, control, communications and computation system functional architecture (1981)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: The functional architecture for an integrated command, control, communications, and computation system applicable to the command and control portion of the NASA End-to-End Data. System is described including the downlink data processing and analysis functions required to support the uplink processes. The functional architecture is composed of four elements: (1) the functional hierarchy which provides the decomposition and allocation of the command and control functions to the system elements; (2) the key system features which summarize the major system capabilities; (3) the operational activity threads which illustrate the interrelationahip between the system elements; and (4) the interfaces which illustrate those elements that originate or generate data and those elements that use the data. The interfaces also provide a description of the data and the data utilization and access techniques.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-166739
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    Electromagnetic backscattering from a sparse distribution of lossy dielectric scatterers (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Electromagnetic backscattering from a sparse distribution of lossy dielectric particles having random orientation and position is studied. The paper begins by using the Foldy approximation to find an equation for the mean field. From this equation, an effective permittivity for the scattering medium is obtained. The correlation of the scattered field is found by employing the distorted Born approximation, i.e., particles embedded in the effective medium are assumed to be single scatterers. The above method is then used to find the backscattering coefficients from a leaf canopy. The leaf canopy is modeled by a half space of dielectric discs that are small in comparison to a wavelength. Numerical results show that the depolarized cross section is a sensitive function of leaf inclination angle statistics.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Radio Science; 16; Jan
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  • 86
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    Limits on the accuracy of correction of trans-ionospheric propagation errors by using ionospheric models based on solar and magnetic indices and local measurements (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Keywords: COMMUNICATIONS AND RADAR
    Type: Radio Science; 16; Jan
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  • 87
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    An adaptive filter for smoothing noisy radar images (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: A spatial domain adaptive Wiener filter for smoothing radar images corrupted by multiplicative noise is presented. The filter is optimum in a minimum mean squared error sense, computationally efficient, and preserves edges in the image better than other filters. The proposed algorithm can also be used for processing optical images with illumination variations that have a multiplicative effect.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE; vol. 69
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  • 88
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    Engineering evaluations and studies. Report for Ku-band studies, exhibit A (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: System performance aspects of the Ku band radar communication hardware and investigations into the Ku band/payload interfaces are discussed. The communications track problem caused by the excessive signal dynamic range at the servo input was investigated. The management/handover logic is discussed and a simplified description of the transmitter enable logic function is presented. Output noise produced by a voltage-controlled oscillator chip used in the SPA return-link channel 3 mid-bit detector is discussed. The deployed assembly (DA) and EA-2 critical design review data are evaluated. Cross coupling effects on antenna servo stability were examined. A series of meetings on the acceptance test specification for the deployed assembly is summarized.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-161018 , R8107-1
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  • 89
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    Optical deep space communication via relay satellite (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The possible use of an optical for high rate data transmission from a deep space vehicle to an Earth-orbiting relay satellite while RF links are envisioned for the relay to Earth link was studied. A preliminary link analysis is presented for initial sizing of optical components and power levels, in terms of achievable data rates and feasible range distances. Modulation formats are restricted to pulsed laser operation, involving bot coded and uncoded schemes. The advantage of an optical link over present RF deep space link capabilities is shown. The problems of acquisition, pointing and tracking with narrow optical beams are presented and discussed. Mathematical models of beam trackers are derived, aiding in the design of such systems for minimizing beam pointing errors. The expected orbital geometry between spacecraft and relay satellite, and its impact on beam pointing dynamics are discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-164855 , JPL-PUB-81-40
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  • 90
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    The design of an ultra-low sidelobe offset-fed 1.22m antenna for use in the broadcasting satellite service (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A feed design and reflector geometry were determined for an ultra low sidelobe offset fed 1.22 meter antenna suitable for use in the 12 GHz broadcasting satellite service. Arbitrary constraints used to evaluate the relative merits of the feed horns and range of f/D geometries are: minimum efficiency of 55 percent, -30 dB first sidelobe level (relative to on axis gain), a 0 dBi plateau beyond the near in sidelobe region, and a Chebyshev polynomial based envelope (borrowed from filter theory) for the region from the -3 dB beamwidth points to the 0 dBi plateau region. This envelope is extremely stringent but the results of this research effort indicate that two steps of corrugated feed and a cluster array of small 1 lambda horns do meet the constraints. A set of performance specifications and a mechanical design suitable for a consumer oriented market in the broadcasting satellite service was developed. Costs for production quantities of 10,000 units/yr. are estimated to be around $150.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-165368
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  • 91
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    Multifrequency broadband polarized horn antenna (1981)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: A corrugated conical horn antenna is simultaneously fed a multiplicity of signals, two for each of five frequencies, with each of a pair of signals fed in each of two orthogonal planes for excitation of a desired spherical hybrid mode. The lowest frequency is fed into the horn through orthogonal pairs of colinear slots, each pair being fed by coaxial tee power dividers. Other signals are fed through a circular waveguide connected to the vertex. The highest frequency signals are fed through orthogonal ports near the far end of the circular waveguide. The intermediate frequency signals are fed through orthogonal ports spaced along the waveguide. Filtering is incorporated for each to maintain isolation and low insertion loss.
    Keywords: COMMUNICATIONS AND RADAR
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  • 92
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    Beat frequency interference pattern characteristics study (1981)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: The frequency spectra and corresponding beat frequencies created by the relative motions between multiple Solar Power Satellites due to solar wind, lunar gravity, etc. were analyzed. The results were derived mathematically and verified through computer simulation. Frequency spectra plots were computer generated. Detailed computations were made for the seven following locations in the continental US: Houston, Tx.; Seattle, Wa.; Miami, Fl.; Chicago, Il.; New York, NY; Los Angeles, Ca.; and Barberton, Oh.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-160958
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    Submillimeter, millimeter, and microwave spectral line catalogue (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A computer accessible catalogue of submillimeter, millimeter and microwave spectral lines in the frequency range between 0 and 3000 GHZ (i.e., wavelengths longer than 100 mu m) is presented which can be used a planning guide or as an aid in the identification and analysis of observed spectral lines. The information listed for each spectral line includes the frequency and its estimated error, the intensity, lower state energy, and quantum number assignment. The catalogue was constructed by using theoretical least squares fits of published spectral lines to accepted molecular models. The associated predictions and their estimated errors are based upon the resultant fitted parameters and their covariances. Future versions of this catalogue will add more atoms and molecules and update the present listings (133 species) as new data appear. The catalogue is available as a magnetic tape recorded in card images and as a set of microfiche records.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-164357 , JPL-PUB-80-23-REV-1
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  • 94
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    Market capture by 30/20 GHz satellite systems, volume 2 (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Results of a telecommunications demand study are presented. Forecasts of demand for 30/20 GHz satellite systems, and the expected build up of traffic on these systems are given as a function of time for each of several operational scenarios.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-165232
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  • 95
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    The 30/20 GHz communications system functional requirements (1981)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: The characteristics of 30/20 GHz usage in satellite systems to be used in support of projected communication requirements of the 1990's are defined. A requirements analysis which develops projected market demand for satellite services by general and specialized carriers and an analysis of the impact of propagation and system constraints on 30/20 GHz operation are included. A set of technical performance characteristics for the 30/20 GHz systems which can serve the resulting market demand and the experimental program necessary to verify technical and operational aspects of the proposed systems is also discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-165301
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    Market capture by 30/20 GHz satellite systems. Volume 1: Executive summary (1981)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: Demand for 30/20 GHz satellite systems over the next two decades is projected. Topics include a profile of the communications market, switched, dedicated, and packet transmission modes, deferred and real-time traffic, quality and reliability considerations, the capacity of competing transmission media, and scenarios for the growth and development of 30/20 GHz satellite communications.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-165231
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    Compressed television transmission: A market survey (1981)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: NASA's compressed television transmission technology is described, and its potential market is considered; a market that encompasses teleconferencing, remote medical diagnosis, patient monitoring, transit station surveillance, as well as traffic management and control. In addition, current and potential television transmission systems and their costs and potential manufacturers are considered.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-168614
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    SAR calibration technology review (1981)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: Synthetic Aperture Radar (SAR) calibration technology including a general description of the primary calibration techniques and some of the factors which affect the performance of calibrated SAR systems are reviewed. The use of reference reflectors for measurement of the total system transfer function along with an on-board calibration signal generator for monitoring the temporal variations of the receiver to processor output is a practical approach for SAR calibration. However, preliminary error analysis and previous experimental measurements indicate that reflectivity measurement accuracies of better than 3 dB will be difficult to achieve. This is not adequate for many applications and, therefore, improved end-to-end SAR calibration techniques are required.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-167534 , REPT-150400-7-F
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  • 99
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    Waveguide cooling system (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An improved system is described for cooling high power waveguides by the use of cooling ducts extending along the waveguide, which minimizes hot spots at the flanges where waveguide sections are connected together. The cooling duct extends along substantially the full length of the waveguide section, and each flange at the end of the section has a through hole with an inner end connected to the duct and an opposite end that can be aligned with a flange hole in another waveguide section. Earth flange is formed with a drainage groove in its face, between the through hole and the waveguide conduit to prevent leakage of cooling fluid into the waveguide. The ducts have narrowed sections immediately adjacent to the flanges to provide room for the installation of fasteners closely around the waveguide channel.
    Keywords: COMMUNICATIONS AND RADAR
    Format: application/pdf
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  • 100
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    Microwave attenuation and brightness temperature due to the gaseous atmosphere: A comparison of JPL and CCIR values (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A sophisticated but flexible radiative transfer program designed to assure internal consistency was used to produce brightness temperature (sky noise temperature in a given direction) and gaseous attenuation curves. The curves, derived from atmospheric models, were compared and a new set was derived for a specified frequency range.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-165027 , JPL-PUB-81-81
    Format: application/pdf
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