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  • COMMUNICATIONS AND RADAR
  • 1980-1984
  • 1975-1979  (166)
  • 1950-1954
  • 1976  (166)
  • 101
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    120 MB/S and 240 MB/S bit synchronizer-signal conditioners for NASA high data rate applications (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Two bit synchronizer-signal conditioners (BSSC) developed for NASA high data rate applications such as earth resources monitoring are described. One BSSC is centered at 120 MB/s and the other at 240 Mb/s. These subsystems are featured out of the total hardware developed because the BSSC is such a key subsystem in determining overall system statistical performance. These units represent an evolution of high data rate BSSC's available at low data rates. Numerous inputs/outputs, control functions, indicators, plus the ability to minimize the effects of various signal perturbations are provided. Examples of allowed perturbations are input level variations, bit rate variance static and dynamic, baseline, transition density, bandlimiting, etc., as well as noise. Emphasis in the past has been primarily concerned only with noise.
    Keywords: COMMUNICATIONS AND RADAR
    Type: International Telemetering Conference; Sep 28, 1976 - Sep 30, 1976; Los Angeles, CA
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    NASA TECHNICAL REPORTS
  • 102
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    Improvements in search and rescue distress alerting and locating using satellites (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: This paper describes a system concept for search and rescue which is capable of making a major contribution to saving lives and reducing the search time for downed aircraft. In addition, a beacon location experiment is described using the Amateur Radio Satellite Corporation Oscar-6 and Oscar-7 spacecraft. The purpose of this experiment was to demonstrate the system concept above by determining the geographical location of a low power 'distress beacon' via satellite based on a single pass of Doppler frequency measurements. Preliminary results are presented showing beacon location recovery on the order of 10 km with indications that an order of magnitude improvement is entirely possible. This experiment is in support of NASA's current exploration into the role satellites might play in providing much needed improvements in the reliability, coverage and accuracy of present search and rescue procedures.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Western Electronic Show and Convention; Sep 14, 1976 - Sep 17, 1976; Los Angeles, CA
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    NASA TECHNICAL REPORTS
  • 103
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    Simulated performance of coded PCM/FM modem on Rician fading channel (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: This paper describes a simulation approach to characterizing the performance of a coded PCM/FM modem operating on the classical Rician fading channel. In particular, we consider the performance of short constraint length convolutional codes in conjunction with Viterbi maximum likelihood decoding. The receiver consists of a narrowband filter followed by an ideal limiter/discriminator. Primary interest is in the bit error probability performance parameterized by both the fading channel and receiver parameters. Particular attention is given to simulating the impulse noise appearing at the discriminator output. This is the 'click' noise caused by encirclements of the origin by the instantaneous signal-plus-noise phasor. Results include the effects of channel memory and narrowband receiver filtering effects on overall bit error probability.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Annual Pittsburgh Conference on Modeling and simulation; Apr 26, 1976 - Apr 27, 1976; Pittsburgh, PA
    Format: text
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  • 104
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    The effects of precipitation on radar target identification and imaging (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The properties of precipitation which will influence radar system design are discussed. The spatial characteristics of rainfall and the sizes and shapes of raindrops are described. The dielectric behavior of water is combined with these characteristics to determine the effects of rain on electromagnetic waves. These effects include: absorption, scatter, noise emission, phase shift, and depolarization.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Atmospheric effects on radar target identification and imaging; Sep 22, 1975 - Oct 03, 1975; Goslar; Germany
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  • 105
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    Interframe transform coding of picture data (1976)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: This semi-tutorial paper describes the process of using orthogonal transforms for the purposes of encoding TV picture data. Results pertaining to a 6:1 data compression experiment using the Walsh-Hadamard transform are included.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Annual Asilomar Conference on Circuits, Systems, and Computers; Nov 03, 1975 - Nov 05, 1975; Pacific Grove, CA
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  • 106
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    OSU participation in the CTS communications link characterization experiment (1976)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A four element self phased array was developed for propagation measurements utilizing the Communication Technology Satellite 11.7 GHz downlink. The parameters of interest in measurements were attenuation, amplitude scintillation, and angle of arrival variability. Simultaneous scintillation measurements were also conducted at 360 MHz, 2.075 GHz, and 30 GHz utilizing ATS-6. The unique movement of ATS-6 during 1976 permitted extensive measurement of scintillation characteristics as a function of path elevation angle.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-152534 , ESL-4299-2 , FR-4299-2
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  • 107
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    ATS-6 mm-wave propagation experiment (1976)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Attenuation on a Space-to-Earth path was measured at 20 GHz for a ground terminal at approximately 1 km elevation in an arid (16 cm annual precipitation) region of eastern Washington state. Precipitation intensity and radiometric sky temperature at 20 GHz were also measured. Attenuation greater than 1 dB was observed only in the presence of wet snow on antenna surfaces. Ten thousand (10,000) hours of radiometric sky temperature data recorded over an 18-month period indicated atmospheric attenuation of 5 to 7 dB during two instances of rain intensity of approximately 1 inch per hour.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-152522
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  • 108
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    Radar Performance Improvement (1976)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The AN/APQ-153 fire control radar modified to provide angle tracking was evaluated for improved performance. The frequency agile modifications are discussed along with the range-rate improvement modifications, and the radar to computer interface. A parametric design and comparison of noncoherent and coherent radar systems are presented. It is shown that the shuttle rendezvous range and range-rate requirements can be made by a Ku-Band noncoherent pulse radar.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-151189 , REPT-2472
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  • 109
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    Investigation of television transmission using adaptive delta modulation principles (1976)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The results are presented of a study on the use of the delta modulator as a digital encoder of television signals. The computer simulation of different delta modulators was studied in order to find a satisfactory delta modulator. After finding a suitable delta modulator algorithm via computer simulation, the results were analyzed and then implemented in hardware to study its ability to encode real time motion pictures from an NTSC format television camera. The effects of channel errors on the delta modulated video signal were tested along with several error correction algorithms via computer simulation. A very high speed delta modulator was built (out of ECL logic), incorporating the most promising of the correction schemes, so that it could be tested on real time motion pictures. Delta modulators were investigated which could achieve significant bandwidth reduction without regard to complexity or speed. The first scheme investigated was a real time frame to frame encoding scheme which required the assembly of fourteen, 131,000 bit long shift registers as well as a high speed delta modulator. The other schemes involved the computer simulation of two dimensional delta modulator algorithms.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-147776
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  • 110
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    Characteristics of magnetospheric radio noise spectra (1976)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Magnetospheric radio noise spectra (30 kHz to 10 MHz) taken by IMP-6 and RAE-2 exhibit time-varying characteristics which are related to spacecraft position and magnetospheric processes. In the mid-frequency range (100-1,000 kHz) intense noise peaks rise by a factor of 100 or more above background; 80% of the peak frequencies are within the band 125 kHz to 600 kHz, and the peak occurs most often (18% of the time) at 280 kHz. This intense mid-frequency noise has been detected at radial distances from 1.3 Re to 60 Re on all sides of the Earth during magnetically quiet as well as disturbed periods. Maximum occurrence of the mid-frequency noise is in the evening to midnight hours where splash-type energetic particle precipitation takes place. ""Magnetospheric lightning'' can be invoked to explain the spectral shape of the observed spectra.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-144751 , RSCR-76-1
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  • 111
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    The propagation and attenuation of complex acoustic waves in treated circular and annular ducts (1976)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The propagation of plane waves and higher order acoustic modes in a circular multisectioned duct was studied. A unique source array consisting of two concentric rings of sources, providing phase and amplitude control in the radial, as well as circumferential direction, was developed to generate plane waves and both spinning and nonspinning higher order modes. Measurements of attenuation and radial mode shapes were taken with finite length liners between the hard wall sections of an anechoically terminated duct. Materials tested as liners included a glass fiber material and both sintered fiber metals and perforated sheet metals with a honeycomb backing. The fundamental acoustic properties of these materials were studied with emphasis on the attenuation of sound by the liners and the determination of local versus extended reaction behavior for the boundary condition. The experimental results were compared with a mathematical model for the multisectioned duct.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-146814
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  • 112
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    Measurements of rain effects on an 18-GHz dual-polarized propagation link (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The paper presents highlights of rain attenuation and depolarization data collected between August 1972 and March 1974 in an experimental setup consisting of a 1.43-km line-of-sight path with 1.22-m diam dual-polarized parabolic reflector antennas at each end. The antennas used question-mark mounted scalar feeds oriented to transmit or receive linearly polarized 17.65-GHz signals having electric field vectors at +45 deg and -45 deg from the vertical. Rain data were collected and analyzed for 24 individual storms in which the rain rate exceeded 10 mm/hr. Received signal levels were sampled once each second and stored by a small digital computer which controlled the experiment and performed preliminary data processing. The results are compared with a theoretical model presented by Wiley et al. (1974). Experimental cross-polarization isolation data are found to agree well with theoretical values, especially at high rain rates where the antenna effects are the least significant.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Radio Science; 11; Dec. 197
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  • 113
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    Far-ultraviolet rocket astronomy program (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The launch of sounding rocket 26.056 DG on 29 October 1976 is described and quick-look results from that mission are given. Also further work on data obtained by 13.118 DG, launched 5 December 1975 is reported.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-153270
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  • 114
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    The OSU self-phased array for propagation measurements using the 11.7 GHz CTS beacon (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A self phased array was developed for propagation measurements on an earth-space path. The 11.7 GHz CTS beacon was used as the signal source. The self phased array was used to measure angle of arrival as well as attenuation and scintillation statistics. The performance of the array is described, and sample data are presented. The tracking capability of the self phased array was also studied. This technique permits fully electronic, nonmechanical satellite tracking, thus simplifying unmanned operation and eliminating severe weather tracking constraints.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-152519 , ESL-4299-1
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  • 115
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    Development of an infrared analyzer following the (1976)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: A radar calibration subsystem for measuring the radar backscattering characteristics of an imaged terrain is described. To achieve the required accuracy for the backscattering coefficient measurement (about 2 dB with 80 percent confidence), the space hardware design includes a means of monitoring the state parameters of the radar. For example, the transmitter output power is sampled and a replica of its output waveform is circulated through the receiver. These are recorded digitally and are used on the ground to determine such radar parameters as the transmitter power and the receiver gain. This part of the data is needed by the ground processor to measure the terrain backscattering characteristics.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-151336 , P76-448 , HAC-REF-D2617
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  • 116
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    Definition and fabrication of an airborne scatterometer radar signal processor (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A hardware/software system which incorporates a microprocessor design and software for the calculation of normalized radar cross section in real time was developed. Interface is provided to decommutate the NASA ADAS data stream for aircraft parameters used in processing and to provide output in the form of strip chart and pcm compatible data recording.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-151345 , PR-3182-3
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  • 117
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    Estimation of the demand for public services communications (1976)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: Market analyses and economic studies are presented to support NASA planning for a communications satellite system to provide public services in health, education, mobile communications, data transfer, and teleconferencing.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-152654 , REPT-76-263-1
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  • 118
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    Experiment definition phase shuttle laboratory, LDRL-10.6 experiment. Shuttle sortie to ground receiver terminal (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: System development and technology are described for a carbon dioxide laser data transmitter capable of transmitting 400 Mbps over a shuttle to ground station link.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-152454
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  • 119
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    Data analysis report on ATS-F COMSAT millimeter wave propagation experiment, part 1 (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The 13/18 GHz COMSAT Propagation Experiment (CPE) was performed to measure attenuation caused by hydrometeors along slant paths from transmitting terminals on the ground to the ATS-6 satellite. The effectiveness of site diversity in overcoming this impairment was also studied. Problems encountered in assembling a valid data base of rain induced attenuation data for statistical analysis are considered. The procedures used to obtain the various statistics are then outlined. The graphs and tables of statistical data for the 15 dual frequency (13 and 18 GHz) site diversity locations are discussed. Cumulative rain rate statistics for the Fayetteville and Boston sites based on point rainfall data collected are presented along with extrapolations of the attenuation and point rainfall data.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-152449
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  • 120
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    Antenna evaluation study for the shuttle multispectral radar, phase 1 (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Critical parameters of the shuttle multispectral radar antenna (SMRA) which most affect antenna performance were identified. A preliminary methematical model is presented for describing SMRA performance under the influence of various physical and environmental factors which might degrade performance. Because user groups have not agreed on optimum frequencies best suited for the broadest range of application, the study incorporates frequencies ranging from 1.2 to 14.5 GHz, as well as a consideration of incidence angles from near nadir to nearly 50 deg.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-151232 , PA00874
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  • 121
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    Bragg interactions in periodic media (1976)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: The interaction of electromagnetic waves of wavelength lambda with periodic structures of spatial period lambda are studied. The emphasis of the work is on Bragg interactions where lambda approximately equal to 2 lambda/N and the Bragg order N takes on the values 1, 2,.... An extended coupled waves (ECW) theory is developed for the case N greater or equal to 2 and the results of the theory are found to compare favorably with the exact results of Floquet theory. Numerous numerical results are displayed as Brillouin diagrams for the first few Bragg orders. Moreover, explicit expressions for coupling coefficients, bandgap shifts and bandgap widths are derived for singly periodic media. Particular note is taken of phase speeding effects.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-149805 , TR-75
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  • 122
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    A review of organizations influencing radio frequency allocations to deep space research (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The charters and functions of various national and international scientific organizations were examined to identify those which have a direct or indirect influence on the allocation of radio frequencies for use in deep space research. Those organizations identified as having the ability to influence frequency allocations are described. A brief description of each organization is provided, and the members who are influential specifically in frequency allocations are listed. The interrelations between the organizations and how they influence allocations are explained.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-149807
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  • 123
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    Applications review for a Space Program Imaging Radar (SPIR) (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The needs, applications, user support, research, and theoretical studies of imaging radar are reviewed. The applications of radar in water resources, minerals and petroleum exploration, vegetation resources, ocean radar imaging, and cartography are discussed. The advantages of space imaging radar are presented, and it is recommended that imaging radar be placed on the space shuttle.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-151182 , GRSU-TR-1
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  • 124
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    Design of a digital compression technique for shuttle television (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The determination of the performance and hardware complexity of data compression algorithms applicable to color television signals, were studied to assess the feasibility of digital compression techniques for shuttle communications applications. For return link communications, it is shown that a nonadaptive two dimensional DPCM technique compresses the bandwidth of field-sequential color TV to about 13 MBPS and requires less than 60 watts of secondary power. For forward link communications, a facsimile coding technique is recommended which provides high resolution slow scan television on a 144 KBPS channel. The onboard decoder requires about 19 watts of secondary power.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-151179 , TRW-29393
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  • 125
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    Statistics of rain-rate estimates for a single attenuating radar (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The effects of fluctuations in return power and the rain-rate/reflectivity relationship, are included in the estimates, as well as errors introduced in the attempt to recover the unattenuated return power. In addition to the Hitschfeld-Bordan correction, two alternative techniques are considered. The performance of the radar is shown to be dependent on the method by which attenuation correction is made.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-X-71257 , X-953-76-289
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  • 126
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    Design study LANDSAT follow-on mission unique communications system (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Spacecraft subsystem design, performance evaluation, and system tradeoffs are presented for the LANDSAT follow-on mission (LF/O) spacecraft to TDRSS link for the transmission of thematic mapper (TM) and multispectral scanner (MSS) data and for the LF/O spacecraft to STDN and other direct users link for the transmission of TM data. Included are requirements definition, link analysis, subsystem and hardware tradeoffs, conceptual selection, hardware definition, and identification of required new technology. Cost estimates of the recommended communication system including both recurring and non recurring costs are discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-144834 , TRW-14897-6007-RU-00
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  • 127
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    Laser Doppler systems in atmospheric turbulence (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The loss of heterodyne signal power for the Marshall Space Flight Center laser Doppler system due to the random changes in the atmospheric index of refraction is investigated. The current status in the physics of low energy laser propagation through turbulent atmosphere is presented. The analysis and approximate evaluation of the loss of the heterodyne signal power due to the atmospheric absorption, scattering, and turbulence are estimated for the conditions of the January 1973 flight tests. Theoretical and experimental signal to noise values are compared. Maximum and minimum values of the atmospheric attenuation over a two way path of 20 km range are calculated as a function of altitude using models of atmosphere, aerosol concentration, and turbulence.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-X-73354
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  • 128
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    Phase modulating with odd and even finite power series of a modulating signal (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Method and apparatus is presented for producing a phase-modulated waveform having a high degree of linearity between the modulating signal and the phase of the modulated carrier signal. Two signals representing finite odd and even power series transformations of the modulating signal are produced and multiplied with two quadrature components of the input carrier signal, respectively. One of the multiplied signals is subtracted from the other and the resulting signal is hard-limited to produce a phase-modulated output signal. The means for producing the two signals representing the odd and even power series of the modulating signal includes means for varying the coefficients of the two power series. By means of an existing computer program, the coefficients of the two power series are selected such that there is an extremely high degree of linearity between the modulating signal and the phase of the modulated carrier signal.
    Keywords: COMMUNICATIONS AND RADAR
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  • 129
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    Feasibility of Coherent and Incoherent Backscatter Experiments from the AMPS Laboratory. Technical Section (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A computer program simulated the spectrum which resulted when a radar signal was transmitted into the ionosphere for a finite time and received for an equal finite interval. The spectrum derived from this signal is statistical in nature because the signal is scattered from the ionosphere, which is statistical in nature. Many estimates of any property of the ionosphere can be made. Their average value will approach the average property of the ionosphere which is being measured. Due to the statistical nature of the spectrum itself, the estimators will vary about this average. The square root of the variance about this average is called the standard deviation, an estimate of the error which exists in any particular radar measurement. In order to determine the feasibility of the space shuttle radar, the magnitude of these errors for measurements of physical interest must be understood.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-144337 , SSL-SER-17-ISSUE-35
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  • 130
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    Design criteria for noncoherent Gaussian channels with MFSK signaling and coding (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: This paper presents data and criteria to assess and guide the design of modems for coded noncoherent communication systems subject to practical system constraints of power, bandwidth, noise spectral density, coherence time, and number of orthogonal signals M. Three basic receiver types are analyzed for the noncoherent multifrequency-shift keying (MFSK) additive white Gaussian noise channel: hard decision, unquantized (optimum), and quantized (soft decision). Channel capacity and computational cutoff rate are computed for each type and presented as functions of the predetection signal-to-noise ratio and the number of orthogonal signals. This relates the channel constraints of power, bandwidth, coherence time, and noise power to the optimum choice of signal duration and signal number.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Communications; COM-24; Oct. 197
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  • 131
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    A SYSTID model for white impulse noise, second edition, volume 2 (1976)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-151711 , CSR-76-2
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  • 132
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    Statistics of the radiated field of a space-to-earth microwave power transfer system (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Statistics such as average power density pattern, variance of the power density pattern and variance of the beam pointing error are related to hardware parameters such as transmitter rms phase error and rms amplitude error. Also a limitation on spectral width of the phase reference for phase control was established. A 1 km diameter transmitter appears feasible provided the total rms insertion phase errors of the phase control modules does not exceed 10 deg, amplitude errors do not exceed 10% rms, and the phase reference spectral width does not exceed approximately 3 kHz. With these conditions the expected radiation pattern is virtually the same as the error free pattern, and the rms beam pointing error would be insignificant (approximately 10 meters).
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-X-73684 , E-9217
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  • 133
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    TDRSS telecommunications system, PN code analysis (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The pseudo noise (PN) codes required to support the TDRSS telecommunications services are analyzed and the impact of alternate coding techniques on the user transponder equipment, the TDRSS equipment, and all factors that contribute to the acquisition and performance of these telecommunication services is assessed. Possible alternatives to the currently proposed hybrid FH/direct sequence acquisition procedures are considered and compared relative to acquisition time, implementation complexity, operational reliability, and cost. The hybrid FH/direct sequence technique is analyzed and rejected in favor of a recommended approach which minimizes acquisition time and user transponder complexity while maximizing probability of acquisition and overall link reliability.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-152579
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  • 134
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    A five-frequency radiometer antenna system feed horn (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The feasibility of operating a five frequency feed as a radiometer for use on board a Nimbus type satellite was investigated. Five narrow band frequencies (6.6, 10.7, 18.5, 21.5 and 33 GHz) were multiplexed onto a single receive feed employing dual linear polarization at each frequency with a better than 25 db isolation between each polarization. The production of a horn design which can illuminate a parabolic reflector segment with an f/D ratio of approximately 0.4, producing an edge illumination of approximately -20 db is described. The final overall design is presented with results showing that this design concept has an acceptable electrical performance.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-152486
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  • 135
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    A synthetic aperture processor using CCD signal processing techniques (1976)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Synthetic aperture radar (SAR) imaging was the most suitable technique for achieving high resolution imagery through atmospheric cloud cover. This feature was important for planetary as well as earth orbiting satellite systems, and for military aircraft applications. Such applications require onboard data processing or wide-band data transmission systems in order to handle the large amounts of raw data produced by such systems. A number of techniques were utilized in implementing SAR processors. Frequency filtering and Fourier transform operations using both optical and digital techniques were utilized in SAR processing.
    Keywords: COMMUNICATIONS AND RADAR
    Type: JPL Conf. on Charge-Coupled Device Technol. and Appls.; p 21-32
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  • 136
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    Snow backscatter in the 1-8 GHz region (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The 1-8 GHz microwave active spectrometer system was used to measure the backscatter response of snow covered ground. The scattering coefficient was measured for all linear polarization combinations at angles of incidence between nadir and 70 deg. Ground truth data consisted of soil moisture, soil temperature profile, snow depth, snow temperature profile, and snow water equivalent. The radar sensitivity to snow water equivalent increased in magnitude with increasing frequency and was almost angle independent for angles of incidence higher than 30 deg, particularly at the higher frequencies. In the 50 deg to 70 deg angular range and in the 6 to 8 GHz frequency range, the sensitivity was typically between -0.4 dB/.1 g/sq cm and -0.5 dB/,1 g/sq cm, and the associated linear correlation coefficient had a magnitude of about 0.8.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-151169 , RSL-TR-177-61
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  • 137
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    Preentry communication design elements for outer planets atmospheric entry probe (1976)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: Four related tasks are discussed for data transmission from a probe prior to entering the atmosphere of Jupiter to an orbiting spacecraft in a trajectory past the planet: (1) link analysis and design; (2) system conceptual design; (3) Doppler measurement analysis; and (4) an electronically despun antenna. For tasks 1, 3, and 4, an analytical approach was developed and combined with computational capability available to produce quantitative results corresponding to requirements and constraints given by NASA, ARC. One constraint having a major impact on the numerical results of the link analysis was the assumption of a nonsteerable antenna on a spinning orbiter. Other constraints included the interplanetary trajectory and the approach trajectory. Because the Jupiter Orbiter Probe (JOP) program is currently in a state of evolution, all requirements and constraints applied during this study are subject to change. However, the relationships of parameters as developed will remain valid and will aid in planning Jupiter missions.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-137880 , D5070 , SCG-60336R
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  • 138
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    Preentry communications study. Outer planets atmospheric entry probe (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A pre-entry communications study is presented for a relay link between a Jupiter entry probe and a spacecraft in hyperbolic orbit. Two generic communications links of interest are described: a pre-entry link to a spun spacecraft antenna, and a pre-entry link to a despun spacecraft antenna. The propagation environment of Jupiter is defined. Although this is one of the least well known features of Jupiter, enough information exists to reasonably establish bounds on the performance of a communications link. Within these bounds, optimal carrier frequencies are defined. The next step is to identify optimal relative geometries between the probe and the spacecraft. Optimal trajectories are established for both spun and despun spacecraft antennas. Given the optimal carrier frequencies, and the optimal trajectories, the data carrying capacities of the pre-entry links are defined. The impact of incorporating pre-entry communications into a basic post entry probe is then assessed. This assessment covers the disciplines of thermal control, power source, mass properties and design layout. A conceptual design is developed of an electronically despun antenna for use on a Pioneer class of spacecraft.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-137876
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  • 139
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    Digital television system design study (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The use of digital techniques for transmission of pictorial data is discussed for multi-frame images (television). Video signals are processed in a manner which includes quantization and coding such that they are separable from the noise introduced into the channel. The performance of digital television systems is determined by the nature of the processing techniques (i.e., whether the video signal itself or, instead, something related to the video signal is quantized and coded) and to the quantization and coding schemes employed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-151125 , R7611-3
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  • 140
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    Final engineering report for Goldstone operations support radar (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The implementation, testing, demonstration, operation, maintenance and evaluation of the equipment are discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-149239 , JPL-TM-33-800
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  • 141
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    Agricultural and hydrological applications of radar (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Program objectives, covering a wide range of disciplines and activities in radar remote sensing, include radar systems development and analysis, data processing and display, and data interpretation in geology, geography and oceanography. Research was focused on the evaluation of radar remote sensing applications in hydrology and agriculture based on data acquired with the Microwave Active Spectrometer (MAS) system. The title, author(s) and abstract of each of the 62 technical reports generated under this contract are appended.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-151107 , RSL-TR-177-62
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  • 142
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    Differential pulse code modulation (1976)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: A differential pulse code modulation (DPCM) encoding and decoding method is described along with an apparatus which is capable of transmission with minimum bandwidth. The apparatus is not affected by data transition density, requires no direct current (DC) response of the transmission link, and suffers from minimal ambiguity in resolution of the digital data.
    Keywords: COMMUNICATIONS AND RADAR
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  • 143
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    Space communication system for compressed data with a concatenated Reed-Solomon-Viterbi coding channel (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A space communication system incorporating a concatenated Reed Solomon Viterbi coding channel is discussed for transmitting compressed and uncompressed data from a spacecraft to a data processing center on Earth. Imaging (and other) data are first compressed into source blocks which are then coded by a Reed Solomon coder and interleaver, followed by a convolutional encoder. The received data is first decoded by a Viterbi decoder, followed by a Reed Solomon decoder and deinterleaver. The output of the latter is then decompressed, based on the compression criteria used in compressing the data in the spacecraft. The decompressed data is processed to reconstruct an approximation of the original data-producing condition or images.
    Keywords: COMMUNICATIONS AND RADAR
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  • 144
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    Test program for transmitter experiment package and heat pipe system for the communications technology satellite (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The test program is described for the 200 watt transmitter experiment package and the variable conductance heat pipe system which are components of the high-power transponder aboard the Communications Technology Satellite. The program includes qualification tests to demonstrate design adequacy, acceptance tests to expose latent defects in flight hardware, and development tests to integrate the components into the transponder system and to demonstrate compatibility.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-X-3455 , E-8832
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  • 145
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    Applications of satellite technology for regional organizations (Project ASTRO) (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The direct arithmetic processing of adaptive delta modulation (ADM) encoded signals, conversion from ADM encoded signals to pulse code modulation (PCM) encoded signals, and conversion from PCM to ADM encoded signals are discussed. It is shown that signals which are ADM encoded can be arithmetically processed directly, without first decoding. Operating on the DM bit stream, and employing only standard digital hardware, the sum, difference and product can be obtained in PCM and ADM format.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-149184
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  • 146
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    Airborne antenna polarization study for the microwave landing system (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The feasibility of the microwave landing system (MLS) airborne antenna pattern coverage requirements are investigated for a large commercial aircraft using a single omnidirectional antenna. Omnidirectional antennas having vertical and horizontal polarizations were evaluated at several different station locations on a one-eleventh scale model Boeing 737 aircraft. The results obtained during this experimental program are presented which include principal plane antenna patterns and complete volumetric coverage plots.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-X-73952
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  • 147
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    Convolutional code performance in the Rician fading channel (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The performance of short constraint length convolutional codes in conjunction with binary phase-shift keyed (BPSK) modulation and Viterbi maximum likelihood decoding on the classical Rician fading channel is examined in detail. Primary interest is in the bit error probability performance as a function of E sub b/N sub 0 parameterized by the fading channel parameters. Fairly general upper bounds on bit error probability performance in the presence of fading are obtained and compared with simulation results in the two extremes of zero channel memory and infinite channel memory. The efficacy of simple block interleaving in combating the memory of the channel is thoroughly explored. Results include the effects of fading on tracking loop performance and the subsequent impact on overall coded system performance. The approach is analytical where possible; otherwise resort is made to digital computer simulation.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Communications; COM-24; June 197
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  • 148
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    Effects of propagation phenomena and frequency allocation on the growth of satellite communications (1976)
    In:  Other Sources
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    Publication Date: 2019-08-27
    Description: The development of new allocations and new frequency and orbit sharing criteria for satellite communications below 10 GHz is discussed. These criteria are dependent on the outcome of current spectrum and orbit utilization and propagation studies addressing such problems as intersystem interference, satellite spacing, positioning, and repositioning, spillover of radio signals across geographic boundaries, and the adverse effects of propagation phenomena. These problems are discussed in relation to preparations for the 1979 General World Administrative Radio Conference.
    Keywords: COMMUNICATIONS AND RADAR
    Type: International Conference on Communications; Jun 14, 1976 - Jun 16, 1976; Philadelphia, PA
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  • 149
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    Definition Study for Space Shuttle Experiments Involving Large, Steerable Millimeter-Wave Antenna Arrays (1976)
    In:  CASI
    Details
    Publication Date: 2019-08-14
    Description: The potential uses and techniques for the shuttle spacelab Millimeter Wave Large Aperture Antenna Experiment (MWLAE) are documented. Potential uses are identified: applications to radio astronomy, the sensing of atmospheric turbulence by its effect on water vapor line emissions, and the monitoring of oil spills by multifrequency radiometry. IF combining is preferable to RF combining with respect to signal to noise ratio for communications receiving antennas of the size proposed for MWLAE. A design approach using arrays of subapertures is proposed to reduce the number of phase shifters and mixers for uses which require a filled aperture. Correlation radiometry and a scheme utilizing synchronous Dicke switches and IF combining are proposed as potential solutions.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-144802 , ESL-3931-3 , FR-3931-3
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  • 150
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    Remarks by Dr. James C. Fletcher at Conference on Satellite Communication and Public Service (1976)
    In:  CASI
    Details
    Publication Date: 2019-08-13
    Description: The present status of communications satellites, together with the future goals and technology developments in use of public service, is assessed. Improvements in design during the last decade considerably cut the cost of their development and launching, and the systems carry information to millions of people on earth. The space shuttles will change the rules in design and make it possible for communications satellites to have multiple frequencies operating at high power.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-NEWS-RELEASE-76-202 , P76-10198 , Dec 09, 1976; Greenbelt, MD; United States
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  • 151
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    NASA teleconference pilot project evaluation for 1975 (1976)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: Tabular data were given to summarize the results of the NASA teleconferencing network pilot project for 1975. The 1,241 evaluation reports received indicate that almost 100,000 man-hours of teleconferences took place. The travel funds reported saved total about $1.44 million, which is about 10% of the NASA travel costs. Subtracting the cost of providing the teleconferencing networks, the net savings reported are $1.28 million (about 9% of the travel costs). The teleconferencing network has proved to be successful in conducting many management meetings and reviews within NASA and its contractors. In spite of difficulties caused by inexperience in teleconferencing and some equipment and circuit problems, the evaluation reports indicated the system was satisfactory in an overwhelming majority of cases.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-X-74161
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  • 152
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    Advanced microwave radiometer antenna system study (1976)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The practicability of a multi-frequency antenna for spaceborne microwave radiometers was considered in detail. The program consisted of a comparative study of various antenna systems, both mechanically and electronically scanned, in relation to specified design goals and desired system performance. The study involved several distinct tasks: definition of candidate antennas that are lightweight and that, at the specified frequencies of 5, 10, 18, 22, and 36 GHz, can provide conical scanning, dual linear polarization, and simultaneous multiple frequency operation; examination of various feed systems and phase-shifting techniques; detailed analysis of several key performance parameters such as beam efficiency, sidelobe level, and antenna beam footprint size; and conception of an antenna/feed system that could meet the design goals. Candidate antennas examined include phased arrays, lenses, and optical reflector systems. Mechanical, electrical, and performance characteristics of the various systems were tabulated for ease of comparison.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-156776 , P76-429 , HAC-REF-D2444
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  • 153
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    Performance of convolutionally encoded noncoherent MFSK modem in fading channels (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The performance of a convolutionally encoded noncoherent multiple-frequency shift-keyed (MFSK) modem utilizing Viterbi maximum-likelihood decoding and operating on a fading channel is described. Both the lognormal and classical Rician fading channels are considered for both slow and time-varying channel conditions. Primary interest is in the resulting bit error rate as a function of the ratio between the energy per transmitted information bit and noise spectral density, parameterized by both the fading channel and code parameters. Fairly general upper bounds on bit error probability are provided and compared with simulation results in the two extremes of zero and infinite channel memory. The efficacy of simple block interleaving in combatting channel memory effects are thoroughly explored. Both quantized and unquantized receiver outputs are considered.
    Keywords: COMMUNICATIONS AND RADAR
    Type: International Telemetering Conference; Sep 28, 1976 - Sep 30, 1976; Los Angeles, CA
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  • 154
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    Timesharing without synchronization (1976)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The capacity region of a multiple-access channel has recently been identified as the convex hull (barred K) of a certain set (K) of points in the first quadrant of the (R1,R2) plane. For a pair of rates in K, a more or less standard random-coding argument can be used to show the existence of a good pair of codes. But for points in barred K-K, it is apparently necessary for the two senders to use some form of time sharing to achieve the desired rates. However, in order to share time, at least one of the senders must have knowledge of the other's phase; and in many practical situations this knowledge does not exist. This paper investigates the problems which arise in coding for multiple-access channels when the senders cannot synchronize with each other.
    Keywords: COMMUNICATIONS AND RADAR
    Type: International Telemetering Conference; Sep 28, 1976 - Sep 30, 1976; Los Angeles, CA
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  • 155
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    A real-time adaptive Hadamard transform video compressor (1976)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: An adaptive video compressor was designed as part of the CTS Digital Video Curriculum Sharing Experiment. The compressor was constructed using field-to-field differencing on fields processed using a Hadamard transform method. The spatial resolution was improved using a fixed-rate, three-mode adaptive system to compress each field.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Seminar on Advances in image transmission techniques; Aug 24, 1976 - Aug 25, 1976; San Diego, CA
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  • 156
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    0.4- to 10-GHz airborne electromagnetic-environment survey of United States urban areas (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: An airborne electromagnetic-environment survey of some U.S. metropolitan areas measured terrestrial emissions within the broad-frequency spectrum from 0.4 to 10 GHz. A Cessna 402 commercial aircraft was fitted with both nadir-viewing and horizon-viewing antennas and instrumentation, including a spectrum analyzer, a 35-mm continuous-film camera, and a magnetic-tape recorder. Most of the flights were made at a nominal altitude of 10,000 ft, and Washington, Baltimore, Philadelphia, New York, and Chicago were surveyed. The 450- to 470-MHz land-mobile UHF band is especially crowded, and the 400- to 406-MHz space bands are less active. Test measurements obtained up to 10 GHz are discussed. Sample spectrum-analyzer photographs were selected from a total of 5750 frames representing 38 hours of data.
    Keywords: COMMUNICATIONS AND RADAR
    Type: International Symposium on Electromagnetic Compatibility; Jul 13, 1976 - Jul 15, 1976; Washington, DC
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  • 157
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    Computer modeling of electromagnetic problems using the geometrical theory of diffraction (1976)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Some applications of the geometrical theory of diffraction (GTD), a high frequency ray optical solution to electromagnetic problems, are presented. GTD extends geometric optics, which does not take into account the diffractions occurring at edges, vertices, and various other discontinuities. Diffraction solutions, analysis of basic structures, construction of more complex structures, and coupling using GTD are discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: International Symposium on Electromagnetic Compatibility; Jul 13, 1976 - Jul 15, 1976; Washington, DC
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  • 158
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    Characterization of the CTS 12 and 14 GHz communications links - Preliminary measurements and evaluation (1976)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The Communications Link Characterization Experiment is designed to characterize the radio frequency links of the Communications Technology Satellite. The experiment is twofold: (1) it will study the natural characteristics in the CTS frequency bands (14 GHz uplink, and 12 GHz downlink) including attenuation and signal degradation due primarily to absorption and scattering induced by precipitation, and (2) it will perform environmental measurements for the characterization of man-made, earth-based signals which could interfere with the uplink frequency bands of the satellite.
    Keywords: COMMUNICATIONS AND RADAR
    Type: International Conference on Communications; Jun 14, 1976 - Jun 16, 1976; Philadelphia, PA
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  • 159
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    A bandwidth-compressive modulation system (1976)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The phrase 'bandwidth-compressive modulation' means that the compression is achieved not by removing redundancy from the data (data compression), but rather by modulating the carrier phase and amplitude with blocks of data bits. The modulation described here is quadrature amplitude shift keying (QASK), a logical extension of quadrature phase shift keying, (QPSK, or quadriphase). QASK is a cost-effective form of combined phase-and-amplitude modulation. That is, n-bit QASK, like most phase-amplitude forms of modulation, requires considerably less transmitter power than comparably performing n-PSK, while among the class of all n-bit phase-modulation types, n-bit QASK performs nearly optimally but requires the least circuit complexity. A simple, unique microwave transmitter is described which provides high-rate QASK modulation with 4:1 bandwidth compression. A suppressed carrier multiple-loop QASK receiver provides the necessary phase tracking, automatic gain control (AGC), and symbol timing.
    Keywords: COMMUNICATIONS AND RADAR
    Type: AIAA PAPER 76-230 , Communications Satellite Systems Conference; Apr 05, 1976 - Apr 08, 1976; Montreal; Canada
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  • 160
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    Dual frequency feed system for the CTS communications link characterization experiment (1976)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The developing, testing and installation of a dual frequency feed assembly were described. The feed has been designed to receive signals in the frequency range 11.7 to 12.2 GHz and transmit signals in the frequency range 14.12 GHz plus or minus 250 MHz. Complete performance data of the feed alone and installed in the 15 foot antenna is included herein. Drawings and descriptive information of the feed assembly are also given.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-144755 , REPT-77-101
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  • 161
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    A 0.4 to 10 GHz airborne electromagnetic environment survey of USA urban areas (1976)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An airborne electromagnetic-environment survey of some U.S. metropolitan areas measured terrestrial emissions within the broad frequency spectrum from 0.4 to 10 GHz. A Cessna 402 commercial aircraft was fitted with both nadir-viewing and horizon-viewing antennas and instrumentation, including a spectrum analyzer, a 35 mm continuous film camera, and a magnetic tape recorder. Most of the flights were made at a nominal altitude of 10,000 feet, and Washington, D. C., Baltimore, Philadelphia, New York, and Chicago were surveyed. The 450 to 470 MHz land-mobile UHF band is especially crowded, and the 400 to 406 MHz space bands are less active. This paper discusses test measurements obtained up to 10 GHz. Sample spectrum analyzer photograhs were selected from a total of 5,750 frames representing 38 hours of data.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-X-71112 , X-952-76-76 , IEEE Intern. Symp. on Electromagnetic Compatibility (EMC), Session2B; Jul 13, 1976 - Jul 15, 1976; Washington, DC; United States
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  • 162
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    Radar data processing and analysis (1976)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Digitized four-channel radar images corresponding to particular areas from the Phoenix and Huntington test sites were generated in conjunction with prior experiments performed to collect X- and L-band synthetic aperture radar imagery of these two areas. The methods for generating this imagery are documented. A secondary objective was the investigation of digital processing techniques for extraction of information from the multiband radar image data. Following the digitization, the remaining resources permitted a preliminary machine analysis to be performed on portions of the radar image data. The results, although necessarily limited, are reported.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-147565 , ERIM-109600-45-F
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  • 163
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    Innovative telecommunications for law enforcement (1976)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The operation of computer-aided dispatch, mobile digital communications, and automatic vehicle location systems used in law enforcement is discussed, and characteristics of systems used by different agencies are compared. With reference to computer-aided dispatch systems, the data base components, dispatcher work load, extent of usage, and design trends are surveyed. The capabilities, levels of communication, and traffic load of mobile digital communications systems are examined. Different automatic vehicle location systems are distinguished, and two systems are evaluated. Other aspects of the application of innovative technology to operational command, control, and communications systems for law enforcement agencies are described.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Western Electronic Show and Convention; Sep 14, 1976 - Sep 17, 1976; Los Angeles, CA
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  • 164
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    Considerations on data compression of synthetic aperture radar images (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: This paper describes some analytical results relative to the effectiveness of applying data compression techniques for efficient transmission of synthetic aperture radar (SAR) signals and images. A Rayleigh target model is assumed in the analysis. It is also assumed that all surface reflectivity information is of interest and needs to be transmitted. Spectral characteristics of radar echo signals and processed images are analyzed. Analytical results generally indicate that due to the lack of high spatial correlation in the Rayleigh distributed radar surface reflectivity, application of data compression to SAR signals and images under the square difference fidelity criterion may be less effective than its application to images obtained using incoherent illumination. On the other hand, if certain random variations in radar images are considered as undesirable, substantial compression ratio may be achieved by removing such variations.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Seminar on Advances in image transmission techniques; Aug 24, 1976 - Aug 25, 1976; San Diego, CA
    Format: text
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  • 165
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    Signal design study for shuttle/TDRSS Ku-band uplink (1976)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The adequacy of the signal design approach chosen for the TDRSS/orbiter uplink was evaluated. Critical functions and/or components associated with the baseline design were identified, and design alternatives were developed for those areas considered high risk. A detailed set of RF and signal processing performance specifications for the orbiter hardware associated with the TDRSS/orbiter Ku band uplink was analyzed. Performances of a detailed design of the PN despreader, the PSK carrier synchronization loop, and the symbol synchronizer are identified. The performance of the downlink signal by means of computer simulation to obtain a realistic determination of bit error rate degradations was studied. The three channel PM downlink signal was detailed by means of analysis and computer simulation.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-150919 , TRW-29210
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 166
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    Radar imaging from a spinning spacecraft (1976)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The feasibility of imaging the surface of Venus using a synthetic aperture radar in a spin stabilized Pioneer class spacecraft operating in an eccentric orbit is studied. Imaging radar fundamentals, constraints, power requirements and data processing considerations are reviewed. Additional effects due to operation from an elliptical orbit with a spinning spacecraft are covered. Recommended spin parameters are determined by simulations. Extensions to include noncoherent integration and stereo coverage are briefly reviewed. The results indicate that resolution on the order of 100 meters can be obtained from a 0.2 eccentricity orbit using a 2 meter antenna and reasonable transmitter power levels.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-137829 , ERIM-115200-2-F
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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