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  • Other Sources  (987)
  • COMMUNICATIONS AND RADAR  (987)
  • 1975-1979  (987)
  • 1
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    Propagation predictions for the HF-range by the Research Institute of the Deutsche Bundespost (1979)
    In:  CASI
    Details
    Publication Date: 2009-11-16
    Description: Long term and short term HF propagation prediction service is described. The long term prediction method is computer based. The short term prediction method is still a manual method which relies mainly on a number of continuous field strength recordings and on the forecaster's ability to interpret the recordings and to combine this information with all available solar-geophysical data. Examples of the predictions are given and are compared with actually observed HF propagation conditions.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NOAA Solar-Terrest. Predictions Proc., Vol. 1; p 25-43
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  • 2
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    A circuit model for electromagnetic properties of waveguide arcs (1979)
    In:  CASI
    Details
    Publication Date: 2006-06-01
    Description: A dielectric model of waveguide arcs is presented to relate measurable electromagnetic quantities to the physical parameters characterizing the breakdown process.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 193-195
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  • 3
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    Assessment of 20 kW S-band transmitter (1979)
    In:  CASI
    Details
    Publication Date: 2006-06-01
    Description: The performance history of the 20-kW S-band transmitter, installed at three 64-meter antennas and six 26-meter antennas in the DSN, is reviewed. A number of failures and discrepancy reports are characteristic of the wearout phase of a failure curve. The type of failures are reviewed and four options toward reducing the number and cost of failures are reviewed. These are: existing (no change), refurbish, redesign and replacement. The options are compared on a ten year life cycle cost basis using FY77 expenditures for existing equipment as a base. It was concluded that benefits, in terms of reduction of outrage time, increase with an increase of expenditure toward improvement.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 186-192
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  • 4
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    Microwave time delays in the DSN 34- and 64-meter antennas (1979)
    In:  CASI
    Details
    Publication Date: 2006-06-01
    Description: The results and methods used to derive data for the recent changes to the DSN 34- and 64-m stations at both S- and X-band frequencies are presented.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 183-185
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  • 5
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    DSS 13 antenna monitor system (1979)
    In:  CASI
    Details
    Publication Date: 2006-06-01
    Description: The development of a monitor system for the DSS 13 antenna is presented. The system checks for accumulator pressures, differential pressures, wind velocity, power supplies, fluid temperatures, and fluid levels. It was concluded that the system performed properly in high winds and correctly reported all malfunctions.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 138-140
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  • 6
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    Carrier tracking loop performance in the presence of strong CW interference (1979)
    In:  CASI
    Details
    Publication Date: 2006-06-01
    Description: Research on the behavior of the carrier tracking loop exposed to a continuous wave irradiation along with Bruno's closed form of approximation for the loop phase error are described.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 130-137
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  • 7
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    Costas loop demodulation of suppressed carrier BPSK signals in the DSN environment: Experimental results obtained at TDL (1979)
    In:  CASI
    Details
    Publication Date: 2006-06-01
    Description: Suppressed carrier binary phase-shift keyed (BPSK) signalling is currently being considered as a design alternative for future DSN telemetry in the multimegabit range. Carrier tracking of such signals is usually achieved by a Costas loop, as opposed to the ordinary phase lock loop. A Costas loop capable of demodulating BPSK signals with data rates up to 1 Msps was designed and constructed and its Doppler tracking performance with respect to a Block 3 receiver was tested at the Telecommunications Development Laboratory (TDL). The compatibility of suppressed carrier signalling with the current radiometric system, specifically Doppler tracking and ranging, was investigated. The experimental results obtained to-date with respect to Doppler tracking are presented.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 94-104
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  • 8
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    Feasibility of inertialess conscan utilizing modified DSN feedsystems (1979)
    In:  CASI
    Details
    Publication Date: 2006-06-01
    Description: The closed-loop conical-scan (conscan) technique has proven to be a useful method for pointing the DSN antennas more accurately than is possible by open-loop methods. As presently implemented, the antenna beam is scanned about the received signal direction by physical movement of the antenna. While straightforward, this approach has at least two disadvantages. Firstly, because of structural distortions, finite angle encoder resolution, and drive servo response, the actual antenna beam direction only approximates the commanded beam direction. Secondly, because of the large mass moved during scan, the rate of scan is severely restricted. If there are significant gain or signal level variations during a scan period, the conscan system interprets these variations as antenna pointing error. Both of these disadvantages would be alleviated in an inertialess conscan system in which the beam scanning was performed electronically. Recently, standard JPL antenna feedhorn software was upgraded to calculate, among other things, asymmetric corrugated horn radiation patterns of the type that would be needed for electronic beam scan. The required horn excitation is discussed and the results were described.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 85-93
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  • 9
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    Antenna feedhorn software upgrade (1979)
    In:  CASI
    Details
    Publication Date: 2006-06-01
    Description: The HYBRIDHORN computer program was developed to serve as an item of general purpose antenna feedhorn design and analysis software. The formulation contains a small flare angle approximation which is subject to question for designs such as the S- and X-band feedhorn. Additionally, the original formulation did not allow azimuthal variation indexes other than unity. The HYBRIDHORN program was upgraded to correct both of these deficiencies. A large flare angle formulation was found. In the upgrade, all of the major program elements were converted to Univac 1108 compatible structured FORTRAN (SFTRAN) for ease of software maintenance. The small and large angle formulations are described and sample numerical results are presented.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 75-84
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  • 10
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    Some effects of quantization on a noiseless phase-locked loop (1979)
    In:  CASI
    Details
    Publication Date: 2006-06-01
    Description: If the VCO of a phase-locked receiver is to be replaced by a digitally programmed synthesizer, the phase error signal must be sampled and quantized. Effects of quantizing after the loop filter (frequency quantization) or before (phase error quantization) are investigated. Constant Doppler or Doppler rate noiseless inputs are assumed. The main result gives the phase jitter due to frequency quantization for a Doppler-rate input. By itself, however, frequency quantization is impractical because it makes the loop dynamic range too small.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 58-66
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  • 11
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    Recovering the spectrum of a narrow-band process from syncopated samples (1979)
    In:  CASI
    Details
    Publication Date: 2006-06-01
    Description: A nonuniform sampling strategy, phase quadrature sampling, in which a process of bandwith B is sampled at rate B in each of two channels where the two channels are pi/2 out of phase at frequency B is described. Phase quadrature sampling is a special case of sampling, where the phase between channels is fixed but arbitrary. A simple method for recovering the spectrum of the input process from syncopated samples is derived. The derivation indicates what values of phase between channels result in lossless sampling.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 47-50
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  • 12
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    Effects of D region ionization on radio wave propagation (1979)
    In:  CASI
    Details
    Publication Date: 2006-01-16
    Description: The effects of anomalous D region ionization upon radio wave propagation are described for the main types of disturbances: sudden ionospheric disturbances, relativistic electron events, magnetic storms, auroral disturbances, polar cap events, and stratospheric warmings. Examples of radio wave characteristics for such conditions are given for the frequencies between the extremely low (3-3000 Hz) and high (3-30 MHz) frequency domains. Statistics on the disturbance effects and radio wave data are given in order to contribute towards the evaluation of possibilities for predicting the radio effects.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA. Marshall Space Flight Center Solar-Terrest. Predictions Proc., Vol. 2; p 617-654
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  • 13
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    Forecasts of geomagnetic activities and HF radio propagation conditions made at Hiraiso/Japan (1979)
    In:  CASI
    Details
    Publication Date: 2006-01-16
    Description: The Hiraiso Branch of RRL prediction techniques are summarized separately for the 27 day recurrent storm and the flare-associated storm. The storm predictions are compared with the actual geomagnetic activities in two ways. The first one is the comparison on a day to day basis. In the second comparison, the accuracy of the storm predictions during 1965-1976 are evaluated. In addition to the storm prediction, short-term predictions of HF radio propagation conditions are conducted at Hiraiso. The HF propagation predictions are briefly described as an example of the applications of the magnetic storm prediction.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NOAA Solar-Terrest. Predictions Proc., Vol. 1; p 182-204
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  • 14
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    Estimation of solar flame influence on radio circuit transmission loss (1979)
    In:  CASI
    Details
    Publication Date: 2006-01-16
    Description: A provisional method for determining the hours and frequencies at which solar flares cause major radiopath absorption increase is presented. This technique is incorporated in a computer program for monthly radio propagation prediction.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NOAA Solar-Terrest. Predictions Proc., Vol. 1; p 67-71
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  • 15
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    PROPHET: An applicaton of propagation forecasting principles (1979)
    In:  CASI
    Details
    Publication Date: 2006-01-16
    Description: A propagation assessment and forecasting terminal, PROPHET, is described. The terminal is a key element of the environmental prediction and assessment system which uses real time solar/geophysical data to provide real time knowledge of propagation conditions. The terminal uses models to translate data from satellite and ground based sources into performance predictions for specific systems.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NOAA Solar-Terrest. Predictions Proc., Vol. 1; p 312-321
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  • 16
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    Radio disturbance warning issuance system (1979)
    In:  CASI
    Details
    Publication Date: 2006-01-16
    Description: A radio disturbance warning issuance system was introduced in the Hiraiso Branch of the Radio Research Laboratories in 1972 to reconstruct the current radio disturbance warning service as a social information service. A description of the new ideas which were experimentally systematized by means of an electronic computer is presented.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NOAA Solar-Terrest. Predictions Proc., Vol. 1; p 223-228
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  • 17
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    Ionosphere-reflected propagation (1979)
    In:  CASI
    Details
    Publication Date: 2006-01-16
    Description: The predictability of those ionospheric parameters relevant to ionosphere-reflected communications is considered along with their optimum utilization. Several excellent original articles and review papers which have been published from time to time dealing with the long term and short term forecasting of ionospheric parameters, radio systems, and modelling needs for ionospheric communications, are covered.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA. Marshall Space Flight Center Solar-Terrest. Predictions Proc., Vol. 2; p 203-216
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  • 18
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    Transionospheric propagation predictions (1979)
    In:  CASI
    Details
    Publication Date: 2006-01-16
    Description: The current status and future prospects of the capability to make transionospheric propagation predictions are addressed, highlighting the effects of the ionized media, which dominate for frequencies below 1 to 3 GHz, depending upon the state of the ionosphere and the elevation angle through the Earth-space path. The primary concerns are the predictions of time delay of signal modulation (group path delay) and of radio wave scintillation. Progress in these areas is strongly tied to knowledge of variable structures in the ionosphere ranging from the large scale (thousands of kilometers in horizontal extent) to the fine scale (kilometer size). Ionospheric variability and the relative importance of various mechanisms responsible for the time histories observed in total electron content (TEC), proportional to signal group delay, and in irregularity formation are discussed in terms of capability to make both short and long term predictions. The data base upon which predictions are made is examined for its adequacy, and the prospects for prediction improvements by more theoretical studies as well as by increasing the available statistical data base are examined.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA. Marshall Space Flight Center Solar-Terrest. Predictions Proc., Vol. 2; p 217-245
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  • 19
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    Radio propagation prediction services in Japan (1979)
    In:  CASI
    Details
    Publication Date: 2006-01-16
    Description: Japanese prediction services for HF radio communications are outlined in relation to prediction method, performance and evaluation. The current prediction is based on the CCIR interim method with some modifications matching to a computer system. The principal service is the monthly median prediction issued regularly three months in advance for various communication circuits. A daily prediction for short distance circuits is being prepared by using real time ionospheric sounding data. An evaluation theory and practice is expected to be introduced in the future prediction service.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NOAA Solar-Terrest. Predictions Proc., Vol. 1; p 212-222
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  • 20
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    Long term solar activity and ionospheric prediction services rendered by the National Physical Laboratory, New Delhi (1979)
    In:  CASI
    Details
    Publication Date: 2006-01-16
    Description: The data base used in solar and ionospheric prediction services is described. Present prediction techniques are discussed and compared with actual observations. Future prediction techniques using computers are also discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NOAA Solar-Terrest. Predictions Proc., Vol. 1; p 118-133
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  • 21
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    The French short term radiopropagation predictions in the decameter band (1979)
    In:  CASI
    Details
    Publication Date: 2006-01-16
    Description: Weekly and daily predictions of the ionospheric characteristics relevant to radio propagation are considered. A description of the techniques involved is given as well as examples showing how the prediction messages are prepared. The short term predictions are confined to restricted geographical areas and are relevant to radio circuits whose terminators are both located inside the same zone. They can be used with a reasonable approximation for circuits less than 3000 km of length whose reflection point lies within a given zone.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NOAA Solar-Terrest. Predictions Proc., Vol. 1; p 12-24
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  • 22
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    Airborne East Coast/Midwest urban survey at 121.5/243 MHz (1979)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: Results of an airborne RF interference measurement survey of the emergency-distress, Search and Rescue frequency bands at 121.5 and 243 MHz at an altitude of 25,000 ft over the U.S. East Coast and Midwest urban areas are presented. Included are a series of minutely median profile plots of antenna-noise temperature computed from RF interference power measurements at the output terminal of a quarter-wavelength monopole antenna, for both daytime and nighttime observations. The greatest value, 450,000 K, of minutely median temperature was recorded over New York City at 121.5 MHz during the day. East Coast urban areas exhibited a day-night effect at 121.5 MHz, where nighttime observations had a median value of 8.6-dB below daytime values; Midwest counterparts did not exhibit a significant day-night effect at 121.5 MHz.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Electromagnetic Compatibility; EMC-21; May 1979
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  • 23
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    Solving the current element problem over lossy half-space without Sommerfeld integrals (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: An approach is presented for efficient computation of the vector potentials arising in the problem of a current element radiating over a lossy half-space. The present approach departs from the conventional ones in that it works primarily with the transform domain representations rather than with the Sommerfeld integrals which are the corresponding spatial domain counterparts. The key step in the present method is to approximate the transforms using a suitable approximation which is valid for a wide range of parameters of practical interest. The approximated transforms can be inverted in a closed form for the horizontal component of the vector potentials and can be expressed in a computationally efficient form for the vertical component. Numerical results illustrating the accuracy of the method are presented and some estimates of comparative computational times are also included.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation; AP-27; Nov. 197
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  • 24
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    Digital techniques for ULF wave polarization analysis (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Digital power spectral and wave polarization analysis are powerful techniques for studying ULF waves in the earth's magnetosphere. Four different techniques for using the spectral matrix to perform such an analysis have been presented in the literature. Three of these techniques are similar in that they require transformation of the spectral matrix to the principal axis system prior to performing the polarization analysis. The differences in the three techniques lie in the manner in which determine this transformation. A comparative study of these three techniques using both simulated and real data has shown them to be approximately equal in quality of performance. The fourth technique does not require transformation of the spectral matrix. Rather, it uses the measured spectral matrix and state vectors for a desired wave type to design a polarization detector function in the frequency domain. The design of various detector functions and their application to both simulated and real data will be presented.
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  • 25
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    Calculated scan characteristics of a large spherical reflector antenna (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A previously published numerical method to calculate the radiation properties of parabolic reflectors has been modified to also include very large spherical reflectors. The method has been verified by comparing the calculated and the measured results for a 120-wavelength spherical reflector.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation; AP-27; May 1979
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  • 26
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    False lock performance of quadriphase receivers (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Quadriphase receivers, like biphase receivers, have the ability to false lock on a sideband on the data modulation. The theory associated with this phenomenon for receivers of binary phase-shift-keying (BPSK), using Costas loop demodulation, has recently been documented in the literature. This paper considers the corresponding theory for receivers of balanced quadriphase-shift-keying (QPSK) employing a quadriphase Costas loop (or equivalent fourth-power loop) for demodulation. Specific closed form expressions for false lock performance are developed and numerically evaluated for the particular case of single pole arm filters and an NRZ data format for each of the two statistically independent quadrature modulations.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Communications; COM-27; Nov. 197
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  • 27
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    Digital and analog communication systems (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The book presents an introductory treatment of digital and analog communication systems with emphasis on digital systems. Attention is given to the following topics: systems and signal analysis, random signal theory, information and channel capacity, baseband data transmission, analog signal transmission, noise in analog communication systems, digital carrier modulation schemes, error control coding, and the digital transmission of analog signals.
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  • 28
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    Interim radio spectrum surveillance station (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Radio frequency interference at NASA's deep space stations has become a serious problem. A radio spectrum surveillance capability at these stations is needed to determine the sources of interference so that preventative measures can be taken. The first phase of a program to develop this capability was the development of a low-cost surveillance station now in operation at the Goldstone Space Communication Complex near Barstow, California. This interim surveillance station is described and findings from the use of this equipment are presented.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 99-107
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  • 29
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    Minimizing the RMS surface distortions from gravity loadings of the 34-m HA-DEC antenna for deep space missions (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The computer analysis of the 34-m HA-DEC antenna by the IDEAS program provided the rms distortions of the surface panels support points for full gravity loadings in the three directions of the basic coordinate system of the computer model. The rms distortions for the gravity vector not in line with any of the three basic directions were solved and contour plotted starting from three surface panels setting declination angle. By inspections of the plots, it was concluded that the setting or rigging angle of -15 degrees declination minimized the rms distortions for sky coverage of plus or minus 22 declination angles to 10 degrees of ground mask.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 94-98
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  • 30
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    Preliminary report on DSN system performance under local weather effects (1979)
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    Publication Date: 2011-08-17
    Description: Local effects of precipitation are studied, and a simplified working model is developed. Experimental results obtained by simulation are in good agreement with the model, showing that it could be an important contribution to system degradation. If this is confirmed, some suggestions for improvement are presented.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 82-88
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  • 31
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    New X-band antenna feeds for the DSN 64-meter stations (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: New X-band antenna feed assemblies with dual-polarization capability are being implemented in the DSN 64-meter stations. Together with dual X-band traveling wave masers, they permit the simultaneous reception of right- and left-hand circular polarization from the Voyager spacecraft. The new feed also includes a dual hybrid mode feedhorn which increases the antenna gain by 0.36 dB over the present feedhorn.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 71-74
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  • 32
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    A generalization of binary minimum shift keying and staggered quadriphase shift keying modulation (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A generalized modulation scheme, which includes minimum shift keying (MSK) and staggered quadriphase shift keying (SQPSK) as special cases, is analyzed. The general modulator is realized as a one-input, two-output sequence transducer whose outputs select the carrier signal for each band. This form of the modulator has the practical advantage of not requiring any RF filtering since there is no actual mixing of the carriers with the modulating signals. It is shown that the optimum demodulator (whether hard-decision or soft-decision) always can make its decisions from the received waveform over two bands when the interference is additive white Gaussian noise, thus generalizing a well-known result for hard decision demodulation of MSK and SQPSK signals. The power spectra of MSK and SQPSK signals are derived to isolate the role played by coherency between the modulating signals and the carriers.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 26-40
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  • 33
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    Radio frequency carrier arraying for near maximum carrier signal-to-noise ratio improvement (1979)
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    Publication Date: 2011-08-17
    Description: Radio frequency arraying of several receiving systems provides signal-to-noise ratio improvement relative to a single receiving system. This report considers radio frequency carrier arraying which provides near maximum signal-to-noise ratio improvement for carrier reception and demodulation.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 99-106
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  • 34
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    Coding for optical channels (1979)
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    Publication Date: 2011-08-17
    Description: In a previous paper Pierce considered the problem of optical communication from a novel viewpoint, and concluded that performance will likely be limited by issues of coding complexity rather than by thermal noise. This paper reviews the model proposed by Pierce and presents some results on the analysis and design of codes for this application.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 70-77
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  • 35
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    Submicrosecond comparison of intercontinental clock synchronization by VLBI and the NTS satellite (1979)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: The intercontinental clock synchronization capabilities of Very Long Baseline Interferometry (VLBI) and the Navigation Technology Satellite (NTS) were compared in May 1978 by using both methods to synchronize the cesium clocks at the NASA Deep Space Net complexes at Madrid, Spain, and Goldstone, California. The VLBI experiments used the Wideband VLBI Data Acquisition System. The Navigation Technology Satellites were used with NTS Timing Receivers developed by the Goddard Space Flight Center. The two methods agreed at about the one-half microsecond level. The VLBI system also obtained long-term stability information on the HP5061A004 cesium standards by measuring delta T/T over four 3- to 4-day intervals, obtaining stability estimates of (1 + or - 1)x10 to the -13th power for the combined timing systems.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 64-69
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  • 36
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    Comparison of phase modulation systems (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Comparison of the energy to noise ratio necessary to obtain a given modulation bit error probability has indicated that three-phase modulation is about 0.75 db superior to four-phase. It is shown that this apparent superiority results entirely from the greater bandwidth required by the three-phase system for the same bit transmission rate. Two further comparison criteria are proposed, which are based on the cut-off rate R sub 0 of the discrete channel created by the modulation system. For the criterion which constrains both the bandwidth and transmitted power, it is shown that four-phase modulation is always superior to three-phase modulation. The conclusion is that three-phase modulation offers no practical advantage over four-phase modulation.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 57-63
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  • 37
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    DSN ground communications facility (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A functional description of the Ground Communications Facilities and its relationships with other elements of the Deep Space Network and NASA Communications Network is presented together with development objectives and goals and comments on implementation activities in support of flight projects.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 19-28
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  • 38
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    DSN command system Mark 3-78 (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The Deep Space Network Command System Mark III-78 implementation and functional operation are described. Software upgrade enables expanded storage capacity in the Deep Space Station Command Processor Assembly. Store-and-forward command data handling is operational for Voyager and Helios. Near-real-time command data handling was retained for Viking and Pioneer.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 11-18
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  • 39
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    The NASA radar entomology program at Wallops Flight Center (1979)
    In:  Other Sources
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    Publication Date: 2016-06-07
    Description: NASA contribution to radar entomology is presented. Wallops Flight Center is described in terms of its radar systems. Radar tracking of birds and insects was recorded from helicopters for airspeed and vertical speed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Radar, Insect Population Ecology, and Pest Management; p 161-169
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  • 40
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    Quantitative Analysis of Radar Returns from Insects (1979)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: When a number of flying insects is low enough to permit their resolution as individual radar targets, quantitative estimates of their aerial density are developed. Accurate measurements of heading distribution using a rotating polarization radar to enhance the wingbeat frequency method of identification are presented.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA. Wallops Flight Center Radar, Insect Population Ecology, and Pest Management; p 131-158
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  • 41
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    Radar program at Western Cotton Research Laboratory (1979)
    In:  Other Sources
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    Publication Date: 2016-06-07
    Description: An entomological radar similar to those used in England is developed. The radar will detect insects in flight and the data will be used for studying insect dispersal.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA. Wallops Flight Center Radar, Insect Population Ecology, and Pest Management; p 159-160
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  • 42
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    Radar observation of known and unknown clear echoes (1979)
    In:  Other Sources
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    Publication Date: 2016-06-07
    Description: Target cross-section as a function of wavelength for known insects, known bird, and dot targets is presented. Tracking data using the time series analysis was tabulated for known birds. Examples were selected from these early works to give entomologists some indication of the types of information that are available by radar as well as examples of the different sources of clear-air radar backscatter.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA. Wallops Flight Center Radar, Insect Population Ecology, and Pest Management; p 113-130
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  • 43
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    Theoretical modelling and experimental data matching for active and passive microwave remote sensing of Earth terrain (1979)
    In:  CASI
    Details
    Publication Date: 2017-10-02
    Description: Two theoretical models were developed to characterize terrain media: a random medium with a variance, a horizontal correlation length; and a homogeneous dielectric containing discrete scatterers. The earth terrain is modelled as layers of such scattering media bounded by air above and half-space below. Matching the theoretical results with experimental data collected from vegetation and snow-ice fields shows that: (1) for observation angles near nadir, rough surface effects are important; (2) for snow-ice field the horizontal correlation length is greater than the vertical correlation length whereas for vegetation field their relative sizes depend on the types of vegetation; (3) the vertically polarized backscattering cross-section is always larger than the horizontally polarized backscattering cross-section for half-space scattering media; (4) for snow field displaying diurnal change, a three-layer model including a thin top layer caused by sunlight illumination must be used; and (5) for a random medium with equal horizontal and vertical correlation lengths, the measured data can also be matched with a corresponding discrete scatterer model.
    Keywords: COMMUNICATIONS AND RADAR
    Type: AGARD Terrain Profiles and Contours in Electromagnetic Wave Propagation; 8 p
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  • 44
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    Satellite-aided mobile radio concepts study: Concept definition of a satellite-aided mobile and personal radio communication system (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The satellite system requires the use of a large satellite antenna and spacecraft array power of about 12 kW or more depending on the operating frequency. Technology developments needed include large offset reflector multibeam antennas, satellite electrical power sybsystems providing greater than 12 kW of power, signal switching hardware, and linearized efficient solid state amplifiers for the satellite-aided mobile band. Presently there is no frequency assignment for this service, and it is recommended that an allocation be pursued. The satellite system appears to be within reasonable extrapolation of the state of the art. It is further recommended that the satellite-aided system spacecraft definition studies and supporting technology development be initiated.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-166646
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  • 45
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    A preliminary study of a very large space radiometric antenna (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An approach used to compute the size of a special radiometric reflector antenna is presented. Operating at 1 GHz, this reflector is required to produce 200 simultaneous contiguous beams, each with a 3 dB footprint of 1 km from an assumed satellite height of 650 km. The overall beam efficiency for each beam is required to be more than 90%.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-80047
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  • 46
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    NASA electronic message experiment and study: Detailed test plans (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A methodology for evaluating the utility of high speed digital facsimile as a component of the projected NASA-wide electronic message network is presented. Equipment checkout, operator familiarization, pretest calibration, and the development of procedures are addressed. An experimental test program of the facsimile message service which will carry duplicates of the actual messages sent by other means is highlighted. Also, an operational test program during which messages will be sent on a regular basis in order to accumulate the information that will be used to evaluate system performance and project future growth is described.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-160007
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  • 47
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    A tactile-output paging communication system for the deaf-blind (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A radio frequency paging communication system that has coded vibrotactile outputs suitable for use by deaf-blind people was developed. In concept, the system consists of a base station transmitting and receiving unit and many on-body transmitting and receiving units. The completed system has seven operating modes: fire alarm; time signal; repeated single character Morse code; manual Morse code; emergency aid request; operational status test; and message acknowledge. The on-body units can be addressed in three ways: all units; a group of units; or an individual unit. All the functions developed were integrated into a single package that can be worn on the user's wrist. The control portion of the on-body unit is implemented by a microcomputer. The microcomputer is packaged in a custom-designed hybrid circuit to reduce its physical size.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-152332
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  • 48
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    Design of a 24-channel transmultiplexer (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The design of a transmultiplexer capable of performing the bilateral conversion between one 1544 kbit/s digital signal (which represents 24 PCM coded voice channels) and two analog group signals (each one containing 12 voice channels in the 60-108 kHz band) is investigated. It is shown that an FIR filter bank required as part of such a transmultiplexer can be realized efficiently by cascading a discrete cosine transform processor and a weighting network. Fast convolution algorithms are derived for evaluating the cosine transform. A method of using the symmetry conditions to reduce the computation rate in the weighting network and an elegant hardware configuration for implementing it are also discussed.
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  • 49
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    On the limitations of the concept of space frequency equivalence (1979)
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    Publication Date: 2019-06-27
    Description: A narrow-band correlation interferometer using directive (large) antennas is equivalent to a wideband correlation interferometer employing isotropic (small) antennas. This concept of space frequency equivalence, due to Kock and Stone, is reexamined and is shown to hold exactly only for the mean or expected values of the correlation interferometer outputs. If their variances are considered, the equivalence disappears, with the variance fo the wideband system always equal to or greater than that of the narrow-band system.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Radio Science; 14; Nov
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  • 50
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    Crosstalk cancellation on linearly and circularly polarized communications satellite links (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The paper discusses the cancellation network approach for reducing crosstalk caused by depolarization on a dual-polarized communications satellite link. If the characteristics of rain depolarization are sufficiently well known, the cancellation network can be designed in a way that reduces system complexity, the most important parameter being the phase of the cross-polarized signal. Relevant theoretical calculations and experimental data are presented. The simplicity of the cancellation system proposed makes it ideal for use with small domestic or private earth terminals.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Radio Science; 14; Nov
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  • 51
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    The 18/30 GHz fixed communications system service demand assessment. Volume 1: Executive summary (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The total demand for voice, video, and data communications services, and satellite transmission services at the 4/6 GHz, 12/14 GHz, and 18/30 GHz frequencies is discussed. Major study objectives, overall methodology, results, and general observations about a satellite systems market characteristics and trends are summarized.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-159546
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  • 52
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    Study of advanced sunflower precision deployable antenna (1979)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: The maximum deployed diameter stowable in shuttle was determined for the original concept and for new more efficient concepts. Estimates of weight, surface accuracy and cost were made for the various configurations. Five critical technologies were identified which would be required to manufacture large solid deployable reflectors. These technologies are concerned with surface accuracy improvement and verification.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-162631 , MEL-79-B-126
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  • 53
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    Future large broadband switched satellite communications networks (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Critical technical, market, and policy issues relevant to future large broadband switched satellite networks are summarized. Our market projections for the period 1980 to 2000 are compared. Clusters of switched satellites, in lieu of large platforms, etc., are shown to have significant advantages. Analysis of an optimum terrestrial network architecture suggests the proper densities of ground stations and that link reliabilities 99.99% may entail less than a 10% cost premium for diversity protection at 20/30 GHz. These analyses suggest that system costs increase as the 0.6 power of traffic. Cost estimates for nominal 20/30 GHz satellite and ground facilities suggest optimum system configurations might employ satellites with 285 beams, multiple TDMA bands each carrying 256 Mbps, and 16 ft ground station antennas. A nominal development program is outlined.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-159961
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  • 54
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    Performance evaluation of telecommunication systems using computer simulation (1979)
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    Publication Date: 2019-06-27
    Description: The SYSTID time domain digital simulation technique is reviewed. A technique is illustrated which estimates the signal to noise ratio at a point in the simulation of a communication system. Signals having a lowpass or bandpass spectra are utilized. Simulation results show the technique to be accurate over a wide range of signal to noise ratios. Examples which illustrate application to both analog and digital communication systems are provided.
    Keywords: COMMUNICATIONS AND RADAR
    Type: ESA SPACECAD 1979: Computer-Aided Design of Electron. for Space Appl.; p 197-206
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  • 55
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    Antenna feed system for receiving circular polarization and transmitting linear polarization (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: An invention is described which provides for receiving a circularly polarized signal from an antenna feed connected to orthogonally spaced antenna elements. It also provides for transmitting a linearly polarized signal through the same feed without switches, and without suffering a 3 dB polarization mismatch loss, using an arrangement of hybrid junctions. The arrangement is comprised of two dividing hybrid junctions, each connected to a different pair of antenna elements and a summing hybrid junction. In one version, a receiver is connected to the summing hybrid junction directly. A diplexer is used to connect a transmitter to only one pair of antenna elements. In another version, designated left and right circularly polarized (LCP and RCP) transmitters are connected to the summing hybrid junction by separate diplexers, and separate LCP and RCP sensitive receivers are connected to the diplexers in order to transmit linearly polarized signals using all four antenna elements while receiving circularly polarized signals as before. An orthomode junction and horn antenna may replace the two dividing hybrid junctions and antenna feed.
    Keywords: COMMUNICATIONS AND RADAR
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  • 56
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    The 30/20 GHz fixed communications systems service demand assessment. Volume 3: Appendices (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The market analysis of voice, video, and data 18/30 GHz communications systems services and satellite transmission services is discussed. Detail calculations, computer displays of traffic, survey questionnaires, and detailed service forecasts are presented.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-159548
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  • 57
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    The 18/30 GHz fixed communications system service demand assessment. Volume 2: Main text (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The total demand for communications services, and satellite transmission services at the 4/6 GHz, 12/14 GHz, and 18/30 GHz frequencies is assessed. The services are voice, video, and data services. Traffic demand, by service, is distributed by geographical regions, population density, and distance between serving points. Further distribution of traffic is made among four major end user groups: business, government, institutions and private individuals. A traffic demand analysis is performed on a typical metropolitan city to examine service distribution trends. The projected cost of C and Ku band satellite systems are compared on an individual service basis to projected terrestrial rates. Separation of traffic between transmission systems, including 18/30 GHz systems, is based on cost, user, and technical considerations.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-159547
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  • 58
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    Study of wrap-rib antenna design (1979)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: The results of a parametric design study conducted to develop the significant characteristics and technology limitations of space deployable antenna systems with aperture sizes ranging from 50 up to 300 m and F/D ratios between 0.5 and 3.0 are presented. Wrap/rib type reflectors of both the prime and offset fed geometry and associated feed support structures were considered. The significant constraints investigated as limitations on achievable aperture were inherent manufacturability, orbit dynamic and thermal stability, antenna weight, and antenna stowed volume. A data base, resulting in the defined maximum achievable aperture size as a function of diameter, frequency and estimated cost, was formed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-162929 , LMSC-D714613
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  • 59
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    Ku-band radar threshold analysis (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The statistics of the CFAR threshold for the Ku-band radar was determined. Exact analytical results were developed for both the mean and standard deviations in the designated search mode. The mean value is compared to the results of a previously reported simulation. The analytical results are more optimistic than the simulation results, for which no explanation is offered. The normalized standard deviation is shown to be very sensitive to signal-to-noise ratio and very insensitive to the noise correlation present in the range gates of the designated search mode. The substantial variation in the CFAR threshold is dominant at large values of SNR where the normalized standard deviation is greater than 0.3. Whether or not this significantly affects the resulting probability of detection is a matter which deserves additional attention.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-160557 , R8001-2
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  • 60
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    The 30/20 GHz fixed communications systems service demand assessment. Volume 3: Annex (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A review of studies forecasting the communication market in the United States is given. The applicability of these forecasts to assessment of demand for the 30/20 GHz fixed communications system is analyzed. Costs for the 30/20 satellite trunking systems are presented and compared with the cost of terrestrial communications.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-159621
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  • 61
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    The 30/20 GHz fixed communications systems service demand assessment. Volume 2: Main report (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A forecast of demand for telecommunications services through the year 2000 is presented with particular reference to demand for satellite communications. Estimates of demand are provided for voice, video, and data services and for various subcategories of these services. The results are converted to a common digital measure in terms of terabits per year and aggregated to obtain total demand projections.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-159620
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  • 62
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    The 30/20 GHz fixed communications systems service demand assessment. Volume 1: Executive summary (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Demand for telecommunications services is forecasted for the period 1980-2000, with particular reference to that portion of the demand associated with satellite communications. Overall demand for telecommunications is predicted to increase by a factor of five over the period studied and the satellite portion of demand will increase even more rapidly. Traffic demand is separately estimated for voice, video, and data services and is also described as a function of distance traveled and city size. The satellite component of projected demand is compared with the capacity available in the C and Ku satellite bands and it is projected that new satellite technology and the implementation of Ka band transmission will be needed in the decade of the 1990's.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-159619
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  • 63
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    Diagnostic procedures for Trend Monitoring System (TMS) communications (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A prototype coaxial cable bus communications sytem was developed to support the trend monitoring system (TMS). Troubleshooting procedures are described at the system level. The procedures can be used by repair personnel to isolate a fault in the TMS and to restore the system to operation by swapping out failed components.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-160453 , MTR-4724 , JSC-14794
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  • 64
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    TMS communications software. Volume 2: Bus interface unit (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A data bus communication system to support the space shuttle's Trend Monitoring System (TMS) and to provide a basis for evaluation of the bus concept is described. Installation of the system included developing both hardware and software interfaces between the bus and the specific TMS computers and terminals. The software written for the microprocessor-based bus interface units is described. The software implements both the general bus communications protocol and also the specific interface protocols for the TMS computers and terminals.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-160452 , MTR-4723-VOL-2 , JSC-14793
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  • 65
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    An efficient approach for computing the geometrical optics field reflected from a numerically specified surface (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: An approach for computing the geometrical optic fields reflected from a numerically specified surface is presented. The approach includes the step of deriving a specular point and begins with computing the reflected rays off the surface at the points where their coordinates, as well as the partial derivatives (or equivalently, the direction of the normal), are numerically specified. Then, a cluster of three adjacent rays are chosen to define a 'mean ray' and the divergence factor associated with this mean ray. Finally, the ampilitude, phase, and vector direction of the reflected field at a given observation point are derived by associating this point with the nearest mean ray and determining its position relative to such a ray.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation; AP-27; Nov. 197
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  • 66
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    An illustrative analysis of technological alternatives for satellite communications (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The demand for satellite communications services in the domestic market is discussed. Two approaches to increasing system capacity are the expansion of service into frequencies presently allocated but not used for satellite communications, and the development of technologies that provide a greater level of service within the currently used frequency bands. The development of economic models and analytic techniques for evaluating capacity expansion alternatives such as these are presented. The satellite orbit spectrum problem, and also outlines of some suitable analytic approaches are examined. Illustrative analysis of domestic communications satellite technology options for providing increased levels of service are also examined. The analysis illustrates the use of probabilities and decision trees in analyzing alternatives, and provides insight into the important aspects of the orbit spectrum problem that would warrant inclusion in a larger scale analysis.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-163281 , SU-24
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  • 67
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    Cost comparison of competing local distribution systems for communication satellite traffic (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The boundaries of market areas which favor various means for distributing communications satellite traffic are considered. The distribution methods considered are: control Earth station with cable access, rooftop Earth stations, Earth station with radio access, and various combinations of these methods. The least cost system for a hypothetical region described by number of users and the average cable access mileage is discussed. The region is characterized by a function which expresses the distribution of users. The results indicate that the least cost distribution is central Earth station with cable access for medium to high density areas of a region combined with rooftop Earth stations or (for higher volumes) radio access for remote users.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-163282 , SU-26
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  • 68
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    Alternative Beam Efficiency Calculations for a Large-aperture Multiple-frequency Microwave Radiometer (LAMMR) (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The fundamental definition of beam efficiency, given in terms of a far field radiation pattern, was used to develop alternative definitions which improve accuracy, reduce the amount of calculation required, and isolate the separate factors composing beam efficiency. Well-known definitions of aperture efficiency were introduced successively to simplify the denominator of the fundamental definition. The superposition of complex vector spillover and backscattered fields was examined, and beam efficiency analysis in terms of power patterns was carried out. An extension from single to dual reflector geometries was included. It is noted that the alternative definitions are advantageous in the mathematical simulation of a radiometer system, and are not intended for the measurements discipline where fields have merged and therefore lost their identity.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-80603
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  • 69
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    Trend Monitoring System (TMS) graphics software (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A prototype bus communications systems, which is being used to support the Trend Monitoring System (TMS) and to evaluate the bus concept is considered. A set of FORTRAN-callable graphics subroutines for the host MODCOMP comuter, and an approach to splitting graphics work between the host and the system's intelligent graphics terminals are described. The graphics software in the MODCOMP and the operating software package written for the graphics terminals are included.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-160454 , MTR-4725 , JSC-14795
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  • 70
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    Weighting in digital synthetic aperture radar processing (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Weighting is employed in synthetic aperture radar (SAR) processing to reduce the sidelobe response at the expense of peak center response height and mainlobe resolution. The weighting effectiveness in digital processing depends not only on the choice of weighting function, but on the fineness of sampling and quantization, on the time bandwidth product, on the quadratic phase error, and on the azimuth antenna pattern. The results of simulations conducted to uncover the effect of these parameters on azimuth weighting effectiveness are presented. In particular, it is shown that multilook capabilities of future SAR systems may obviate the need for consideration of the antenna pattern, and that azimuth time-bandwidth products of over 200 are probably required before the digital results begin to approach the ideal results.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-162684 , JPL-PUB-79-94
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  • 71
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    Shuttle orbiter S-band payload communications equipment design evaluation (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The analysis of the design, and the performance assessment of the Orbiter S-band communication equipment are reported. The equipment considered include: network transponder, network signal processor, FM transmitter, FM signal processor, payload interrogator, and payload signal processor.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-160438 , R7911-4
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  • 72
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    High frequency scattering from a thin lossless dielectric slab (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A solution for scattering from a thin dielectric slab is developed based on geometrical optics and the geometrical theory of diffraction with the intention of developing a model for a windshield of a small private aircraft for incorporation in an aircraft antenna code. Results of the theory are compared with experimental measurements and moment method calculations showing good agreement. Application of the solution is also addressed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-162564 , OSU-TR-710964-4
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  • 73
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    Electromagnetic power absorber (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A structure is presented with a surface portion of dielectric material which passes electromagnetic radiation and with a portion below the surface which includes material that absorbs the radiation, the face of the structure being formed with numerous steep ridges. The steepness of the dielectric material results in a high proportion of the electromagnetic energy passing through the surface for absorption by the absorbing material under the surface. A backing of aluminum or other highly heat-conductive and reflective material lies under the face and has very steep protuberances supporting the absorbing and dielectric materials.
    Keywords: COMMUNICATIONS AND RADAR
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  • 74
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    Resonant frequency of microstrip antennas calculated from TE-excitation of an infinite strip embedded in a grounded dielectric slab (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The calculation of currents induced by a plane wave normally incident upon an infinite strip embedded in a grounded dielectric slab is used to infer the resonant width (or frequency) of rectangular microstrip antennas. By placing the strip inside the dielectric, the effect of a dielectric cover of the same material as the substrate can be included in the calculation of resonant frequency. A comparison with measured results indicated agreement of 1 percent or better for rectangular microstrip antennas constructed on Teflon-fiberglass substrate.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-80190
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  • 75
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    Orbiter CIU/IUS communications hardware evaluation (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The DOD and NASA inertial upper stage communication system design, hardware specifications and interfaces were analyzed to determine their compatibility with the Orbiter payload communications equipment (Payload Interrogator, Payload Signal Processors, Communications Interface Unit, and the Orbiter operational communications equipment (the S-Band and Ku-band systems). Topics covered include (1) IUS/shuttle Orbiter communications interface definition; (2) Orbiter avionics equipment serving the IUS; (3) IUS communication equipment; (4) IUS/shuttle Orbiter RF links; (5) STDN/TDRS S-band related activities; and (6) communication interface unit/Orbiter interface issues. A test requirement plan overview is included.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-160404 , R7911-5
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  • 76
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    Operational procedures for ground station operation: ATS-3 Hawaii-Ames satellite link experiment (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Hardware description and operational procedures for the ATS-3 Hawaii-Ames satellite computer link are presented in basic step-by-step instructions. Transmit and receive channels and frequencies are given. Details such as switch settings for activating the station to the sequence of turning switches on are provided. Methods and procedures for troubleshooting common problems encountered with communication stations are also provided.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-81155 , A-8011
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  • 77
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    Application of advanced on-board processing concepts to future satellite communications systems: Bibliography (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Abstracts are presented of a literature survey of reports concerning the application of signal processing concepts. Approximately 300 references are included.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-159684 , MTR-3787-VOL-2
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  • 78
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    Low sidelobe level low-cost earth station antennas for the 12 GHz broadcasting satellite service (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: An experimental investigation of the performance of 1.22 m and 1.83 m diameter paraboloid antennas with an f/D ratio of 0.38 and using a feed developed by Kumar is reported. It is found that sidelobes below 30 dB can be obtained only if the paraboloids are relatively free of surface errors. A theoretical analysis of clam shell distortion shows that this is a limiting factor in achieving low sidelobe levels with many commercially available low cost paraboloids. The use of absorbing pads and small reflecting plates for sidelobe reduction is also considered.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-159703
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  • 79
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    The NASA bus communications listening device software (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The development of the bus listener is presented. Special software was developed to control the 'bus interface units' (BIU) connecting each of these devices to a communications cable to form the bus communication network. The code used in the BTU is described.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-160384 , MTR-4729 , JSC-16054
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  • 80
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    Application of advanced on-board processing concepts to future satellite communications systems (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: An initial definition of on-board processing requirements for an advanced satellite communications system to service domestic markets in the 1990's is presented. An exemplar system architecture with both RF on-board switching and demodulation/remodulation baseband processing was used to identify important issues related to system implementation, cost, and technology development.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-159682 , MTR-3787-VOL-1
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  • 81
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    Central Computational Facility CCF communications subsystem options (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A MITRE study which investigated the communication options available to support both the remaining Central Computational Facility (CCF) computer systems and the proposed U1108 replacements is presented. The facilities utilized to link the remote user terminals with the CCF were analyzed and guidelines to provide more efficient communications were established.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-160383 , MTR-4728 , JSC-16006
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  • 82
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    Control of ELT false alarms (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The statistics of emergency locator transmitter (ELT) alarms are presented. The primary sources of data include ELT Incident Logs, Service Difficulty Reports, and Frequency Interference Reports. The number of reported and unreported alarms is discussed, as are seasonal variations, duration of ELT transmissions, and cost of silencing. Origin, causes, and possible strategies for reducing the impact of alarms on the aviation community are considered.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-162502 , PUBL-1362-01-1-2032
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  • 83
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    Handbook for the estimation of microwave propagation effects: Link calculations for earth-space paths (path loss and noise estimation) (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A single model for a standard of comparison for other models when dealing with rain attenuation problems in system design and experimentation is proposed. Refinements to the Global Rain Production Model are incorporated. Path loss and noise estimation procedures as the basic input to systems design for earth-to-space microwave links operating at frequencies from 1 to 300 GHz are provided. Topics covered include gaseous absorption, attenuation by rain, ionospheric and tropospheric scintillation, low elevation angle effects, radome attenuation, diversity schemes, link calculation, and receiver noise emission by atmospheric gases, rain, and antenna contributions.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-165002 , TR-1 , P-7376-TR1
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  • 84
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    Optical communication with two-photon coherent states. II - Photoemissive detection and structured receiver performance (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: In a previous paper (1978), the authors developed a method of analyzing the performance of two-photon coherent state (TCS) systems for free-space optical communications. General theorems permitting application of classical point process results to detection and estimation of signals in arbitrary quantum states were derived. The present paper examines the general problem of photoemissive detection statistics. On the basis of the photocounting theory of Kelley and Kleiner (1964) it is shown that for arbitrary pure state illumination, the resulting photocurrent is in general a self-exciting point process. The photocount statistics for first-order coherent fields reduce to those of a special class of Markov birth processes, which the authors term single-mode birth processes. These general results are applied to the structure of TCS radiation, and it is shown that the use of TCS radiation with direct or heterodyne detection results in minimal performance increments over comparable coherent-state systems. However, significant performance advantages are offered by use of TCS radiation with homodyne detection. The abstract quantum descriptions of homodyne and heterodyne detection are derived and a synthesis procedure for obtaining quantum measurements described by arbitrary TCS is given.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Information Theory; IT-25; Mar. 197
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  • 85
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    A comparison of theoretical and experimental video compression designs (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: This paper compares theoretical and experimental picture compression designs, for images processed in 8 x 8 blocks using the Walsh-Hadamard transform (WHT). The optimum picture compression design is well known, if the mean-square error (mse) is used as the measure of distortion, and if it is assumed that the video process is a stationary first-order Markov process with a Gaussian distribution. This theoretical design gives useful results when the transform processing is done on full pictures, but gives inferior results (relative to empirical design) when transform processing is done on small 8 x 8 blocks. The use of non-Gaussian distributions for the transform components fails to improve this poor performance, which is due to the nonstationary nature of the video process. An experimentally based design procedure, which considers nonstationarity, yields significantly improved mse and subjective performance.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Electromagnetic Compatibility; EMC-21; Feb. 197
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  • 86
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    On the optimality of the MAP estimation loop for carrier phase tracking BPSK and QPSK signals (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Starting with MAP estimation theory as a basis for optimally estimating carrier phase of BPSK and QPSK modulations, it is shown in this paper that the closed loop phase trackers, which are motivated by this approach, are indeed closed loop optimum in the minimum mean-square phase tracking jitter sense. The corresponding squaring loss performance of these so-called MAP estimation loops is compared with that of more practical implementations wherein the hyperbolic tangent nonlinearity is approximated by simpler functions.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Communications; COM-27; Jan. 197
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  • 87
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    Transform approach to electromagnetic scattering (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: In this paper, a comprehensive review of the Fourier transform technique as applied to the problem of high-frequency scattering is presented and the concepts of the spectral theory of diffraction (STD) are introduced. In contrast to the more commonly employed ray-optical method for high-frequency scattering, the STD approach interprets the scattered field as the spectrum, or the Fourier transform of the induced current on the scatterer. Such an interpretation offers several important advantages: uniform nature of representation, capacity to improve and extend the ray-optical formulas in a systematic manner, and convenient accuracy tests for the results. Methods for combining integral equation methods with the Galerkin procedure and asymptotic techniques in the transform domain are described, and representative examples illustrating the application of the spectral approach are included.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE; vol. 67
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  • 88
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    TMS communications software. Volume 1: Computer interfaces (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A prototype bus communications system, which is being used to support the Trend Monitoring System (TMS) as well as for evaluation of the bus concept is considered. Hardware and software interfaces to the MODCOMP and NOVA minicomputers are included. The system software required to drive the interfaces in each TMS computer is described. Documentation of other software for bus statistics monitoring and for transferring files across the bus is also included.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-160451 , MTR-4723-VOL-1 , JSC-14792
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  • 89
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    TMS communications hardware. Volume 2: Bus interface unit (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A prototype coaxial cable bus communication system used in the Trend Monitoring System to interconnect intelligent graphics terminals to a host minicomputer is described. The terminals and host are connected to the bus through a microprocessor-based RF modem termed a Bus Interface Unit (BIU). The BIU hardware and the Carrier Sense Multiple Access Listen-While-Talk protocol used on the network are described.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-160450 , MTR-4721-VOL-2 , JSC-14723
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  • 90
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    TMS communications hardware. Volume 1: Computer interfaces (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A prototpye coaxial cable bus communications system was designed to be used in the Trend Monitoring System (TMS) to connect intelligent graphics terminals (based around a Data General NOVA/3 computer) to a MODCOMP IV host minicomputer. The direct memory access (DMA) interfaces which were utilized for each of these computers are identified. It is shown that for the MODCOMP, an off-the-shell board was suitable, while for the NOVAs, custon interface circuitry was designed and implemented.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-160449 , MTR-H721-VOL-1 , JSC-14682
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  • 91
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    Technique to determine location of radio sources from measurements taken on spinning spacecraft (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The procedure developed to extract average source direction and average source size from spin-modulated radio astronomy data measured on the IMP-6 spacecraft is described. Because all measurements are used, rather than just finding maxima or minima in the data, the method is very sensitive, even in the presence of large amounts of noise. The technique is applicable to all experiments with directivity characteristics. It is suitable for onboard processing on satellites to reduce the data flow to Earth. The application to spin-modulated nonpolarized radio astronomy data is made and includes the effects of noise, background, and second source interference. The analysis was tested with computer simulated data and the results agree with analytic predictions. Applications of this method with IMP-6 radio data have led to: (1) determination of source positions of traveling solar radio bursts at large distances from the Sun; (2) mapping of magnetospheric radio emissions by radio triangulation; and (3) detection of low frequency radio emissions from Jupiter and Saturn.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-80598
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  • 92
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    A survey of airborne radar systems for deployment on a High Altitude Powered Platform (HAPP) (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A survey was conducted to find out the system characteristics of commercially available and unclassified military radars suitable for deployment on a stationary platform. A total of ten domestic and eight foreign manufacturers of the radar systems were identified. Questionnaires were sent to manufacturers requesting information concerning the system characteristics: frequency, power used, weight, volume, power radiated, antenna pattern, resolution, display capabilities, pulse repetition frequency, and sensitivity. A literature search was also made to gather the system characteristics information. Results of the survey are documented and comparisons are made among available radar systems.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-156860 , CSC-TM-79-6294
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  • 93
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    Public service user terminus study compendium of terminus equipment (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: General descriptions and specifications are given for equipments which facilitate satellite and terrestrial communications delivery by acting as interfaces between a human, mechanical, or electrical information generator (or source) and the communication system. Manufactures and suppliers are given as well as the purchase, service, or lease costs of various products listed under the following cateories: voice/telephony/facsimile equipment; data/graphics terminals; full motion and processes video equipment; and multiple access equipment.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-159941
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  • 94
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    Telephone multiline signaling using common signal pair (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: An operator can rapidly and automatically produce coded electrical signals by manipulating mechanical thumb wheel switches so as to instruct a service center to connect any number of telephone lines to the console thus enabling the operator to listen and/or talk over several lines simultaneously. The system includes an on-site console having several mechanically operated thumb wheel switches to which the desired lines to be connected can be dialed in. Electrical coded signals are fed to a number of banks of line AND gates representing units, tens and hundreds, a group of channel gates, and a command gate. These signals are gated out in a controlled manner to an encoder which generates tones that are transmitted over a single line to a communication service center.
    Keywords: COMMUNICATIONS AND RADAR
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  • 95
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    A cross impact methodology for the assessment of US telecommunications system with application to fiber optics development: Executive summary (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A cross impact model of the U.S. telecommunications system was developed. For this model, it was necessary to prepare forecasts of the major segments of the telecommunications system, such as satellites, telephone, TV, CATV, radio broadcasting, etc. In addition, forecasts were prepared of the traffic generated by a variety of new or expanded services, such as electronic check clearing and point of sale electronic funds transfer. Finally, the interactions among the forecasts were estimated (the cross impacts). Both the forecasts and the cross impacts were used as inputs to the cross impact model, which could then be used to stimulate the future growth of the entire U.S. telecommunications system. By varying the inputs, technology changes or policy decisions with regard to any segment of the system could be evaluated in the context of the remainder of the system. To illustrate the operation of the model, a specific study was made of the deployment of fiber optics, throughout the telecommunications system.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-135209 , UDR-TR-79-17
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  • 96
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    Azimuth correlator for real-time synthetic aperture radar image processing (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: An azimuth correlator architecture is defined wherein a number of serial range-line buffer memories are cascaded such that the output stages of all buffer memories together form a complete and unique range bin in the azimuthal dimension at any given time. A range bin is automatically read out of the last stages of the registers in parallel on a range line sample-by-sample basis for subsequent range migration correction and correlation. Range migration correction is performed on the range bins by effectively varying the length of a delay register at the output of each range-line buffer memory. The corrected range bin output from the delay registers is then correlated with a Doppler reference function to form an image element on a real-time basis.
    Keywords: COMMUNICATIONS AND RADAR
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  • 97
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    Design of a video teleconference facility for a synchronous satellite communications link (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The system requirements, design tradeoffs, and final design of a video teleconference facility are discussed, including proper lighting, graphics transmission, and picture aesthetics. Methods currently accepted in the television broadcast industry are used in the design. The unique problems associated with using an audio channel with a synchronous satellite communications link are discussed, and a final audio system design is presented.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TP-1376 , E-9202
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  • 98
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    Airborne Electronically Steerable Phased Array (AESPA) program (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The basic concept and design of a flatplate-fed transmission array are described and system performance requirements are summarized. Particular emphasis is given to the design of the aperture, the radiating element, the phase shifter, the flatplate feed, and the mechanical support structure. Fabrication and testing techniques are considered. Of the three major parameters of interest in demonstrating the performance capabilities of the transmissive array, beamwidth was shown to be the least sensitive to system amplitude and phase errors. Beam pointing angle was also shown to be relatively insensitive to errors. Close agreement between measured and calculated values was found for array gain. The greatest difference was found for array sidelone level.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-161395 , NAS 1.26:161395 , U1-771401-F
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  • 99
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    Preliminary study of rain effects on radar scattering from water surfaces (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Preliminary wave-tank results indicate that radar scatter from water surfaces is severely affected by rain at low but not at high wind speeds. The effect is governed by both the rain rate and droplet size. A simple experiment to check this phenomenon is described.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Journal of Oceanic Engineering; OE-4; Jan. 197
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  • 100
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    A prototype DSN X-S band feed: DSS 13 application (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: A prototype X-S band horn feed for future use at various DSN sites, dealing with the testing of the final fabricated feed at DSS 13 are discussed. Measured feedhorn patterns are presented, and efficiencies calculated. Preliminary results of system noise temperature and 26-m antenna system gain measurements are presented. Some measurements leading to an improved second generation feed are described. The results of the field measurements indicate that this horn will perform as originally specified and required. The tests for the second generation feed have indicated the potential cause of minor X-band moding.
    Keywords: COMMUNICATIONS AND RADAR
    Type: SR-3 , The Deep Space Network; p 51-60
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