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  • COMMUNICATIONS AND RADAR
  • 2000-2004
  • 1995-1999
  • 1980-1984  (170)
  • 1975-1979  (166)
  • 1970-1974
  • 1980  (170)
  • 1976  (166)
Collection
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Years
  • 2000-2004
  • 1995-1999
  • 1980-1984  (170)
  • 1975-1979  (166)
  • 1970-1974
Year
  • 1
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    Alias lock behavior of sampled-data Costas loops (1980)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: The potential false-lock problem associated with the sampled data type of Costas loop implementation is addressed in this paper. The term 'alias lock' is used here to differentiate this type of false lock behavior from the data sideband false lock behavior of analog Costas loops. It is shown that the sampled-data version of the conventional Costas loop, sampled at a rate 1/T(s), can alias lock at frequencies that are multiples of 1/2T(s) away from the carrier frequency. It is also shown that the alias lock problem of the sampled data version of the Costas loop with hard-limited in-phase channel is further compounded by the potential occurrence of false lock frequencies at rational multiples of 1/2T(s) away from the carrier. The false lock S-curves of I-Q loops and decision-directed I-Q loops are investigated in detail, with and without additive noise. Close agreement between theory and earlier experimental results is also demonstrated.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Communications; COM-28; Aug. 198
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  • 2
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    Comparison of three-phase modulation with two-phase and four-phase modulation (1980)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: For a constant added noise density at high signal-to-noise ratios and for the same error rate, three-phase PSK requires about 0.75 dB less energy per bit than two-phase or four-phase PSK. However, at very low signal-to-noise ratios, three-phase PSK requires about 0.74 dB more energy per bit of channel capacity than two-phase or four-phase PSK.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Communications; COM-28; July 198
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  • 3
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    Multiple scattering effects on wave propagation due to rain (1980)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The paper examines the multiple scattering of microwaves due to rain and the resulting incoherent intensity for a plane wave incident on a plane-parallel rain region. General formulations of the transfer equation using Stokes parameters are presented, and an extinction matrix which takes into account depolarization effects and nonspherical droplet shape is introduced. Scattering characteristics are calculated for spherical droplets using the Mie solution and the Laws-Parsons distributions. The ratios of incoherent to coherent received powers are calculated at 30 GHz for rain rates of 12.5, 50, 100, and 150 mm/h, rain thicknesses of 3 km and 10 km, and fields of view of 1.5, 5, and 15 deg.
    Keywords: COMMUNICATIONS AND RADAR
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  • 4
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    Prediction of attenuation by rain (1980)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A new model is presented for the prediction of attenuation by rain on either terrestrial or slant earth-to-space propagation paths. The model was developed using geophysical observations of the statistics of point rain rate, of the horizontal structure of rainfall, and of the vertical temperature structure of the atmosphere. The model was tested by comparison with attenuation distribution observations. The results show excellent agreement; the observations differ from model predictions by less than the rms deviations predicted by the model.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Communications; COM-28; Sept
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  • 5
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    Refraction of microwave signals by water vapor (1980)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Tropospheric water vapor causes a refractive path length effect which is typically 5-10% of the 'dry' tropospheric effect and as large as several meters at elevation angles below 5 deg. The vertical water vapor profile is quite variable, and measurements of intensive atmospheric parameters such as temperature and humidity limited to the surface do not adequately predict the refractive effect. It is suggested that a water vapor refraction model that is a function of the amount of precipitable water alone can be successful at low elevation angles. From an extensive study of numerical ray tracings through radiosonde balloon data, such a model has been constructed. The model predicts the effect at all latitudes and elevation angles between 2 and 10 deg to an accuracy of better than 4% (11 cm at 3 deg elevation angle).
    Keywords: COMMUNICATIONS AND RADAR
    Type: Journal of Geophysical Research; 85; Sept. 20
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  • 6
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    The Communications Technology Satellite /CTS/ Program (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The purposes of the joint Canadian-U.S. Communications Technology Satellite (CTS) Program are (1) to conduct satellite communication systems experiments using the 12- and 14-GHz bands and low-cost transportable ground terminals, (2) to develop and flight test a power amplifier tube having a greater than 50% efficiency with a saturated power output of 200 W at 12 GHz, (3) to develop and flight test a lightweight extendible solar array with an initial power output greater than 1 kW, and (4) to develop and flight test a 3-axis stabilization system to maintain accurate antenna boresight positioning on a spacecraft with flexible appendages. Brief descriptions of these experiments and of the ground facilities are provided.
    Keywords: COMMUNICATIONS AND RADAR
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  • 7
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    Television applications of interline-transfer CCD arrays (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The design features and characteristics of interline transfer (ILT) CCD arrays with 190 x 244 and 380 x 488 image elements are reviewed, with emphasis on optional operating modes and system application considerations. It was shown that the observed horizontal resolution for a TV system using an ILT image sensor can approach the aperture response limit determined by photosensor site width, resulting in enhanced resolution for moving images. Preferred camera configurations and read out clocking modes for maximum resolution and low light sensitivity are discussed, including a very low light level intensifier CCD concept. Several camera designs utilizing ILT-CCD arrays are described. These cameras demonstrate feasibility in applications where small size, low-power/low-voltage operation, high sensitivity and extreme ruggedness are either desired or mandatory system requirements.
    Keywords: COMMUNICATIONS AND RADAR
    Type: JPL Conf. on Charge-Coupled Device Technol. and Appls.; p 152-156
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  • 8
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    Television cameras employing solid-state imaging sensors for manned spacecraft applications (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The Space Shuttle television system incorporates a versatile complement of TV equipment which allows the positioning, quantity, and performance capabilities of the multiple TV cameras to vary as dictated by the particular mission. However, current TV camera technology employing glass enclosed, vacuum processed image sensors results in a bulky device that restricts its location and versatility. Problems and potential solutions that can be achieved through the employment of solid-state image sensors for both monochrome and color applications are discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: JPL Conf. on Charge-Coupled Device Technol. and Appls.; p 126-128
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  • 9
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    Command detector SNR estimator and lock status monitor circuitry (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A breadboard of the command detector signal-to-noise-ratio estimator and lock status monitor was built on a wire-wrap card. The breadboard was integrated with the standard command detector, and its performance was measured. The design, design constraints, and construction of the breadboard are described. The performance is shown to agree with the theoretical model.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 42-51
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  • 10
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    The scattering of obliquely incident plane waves from a corrugated conducting surface (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A physical optics solution is presented for the scattering of plane waves from a perfectly conducting corrugated surface in the case of waves incident from an arbitrary direction and for an observer far from the surface. This solution is used to compute the radar cross section of the surface in the case of backscatter from irregular (i.e., stochastic) corrugations. An interesting feature of the solution is the occurrence of singularities in the scattered fields. These singularities appear to be a manifestation of focusing by the surface at its 'stationary' points. Whether or not the singularities occur in the solution depends on the manner in which one restricts the analysis to the far-field.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation; AP-24; Nov. 197
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  • 11
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    Radio frequency boresight analysis of the low cost 64-meter antenna (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Configurations (two) of the reflector-only assemblies, using different width backup cones, are analyzed for RF boresight direction changes and wind distortions. The wider backup cone is best for minimum weight; however, there is an optimum weight which minimizes the RF boresight errors for a wind load that produces the maximum pitching moment of both configurations.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 128-135
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  • 12
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    Magnitude of 64-m elevation axis movements due to alidade temperature changes (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: In projected very-long baseline interferometry (VLBI) work a reference point for 64-m antennas is the intersection of the elevation and azimuth axes. A minimum-level effort at DSS 14 to determine the magnitude of the effect of diurnal changes in the temperature of the alidade legs on the height of the elevation axis is described. The thermal expansion between the lowest recorded temperature -3 C (27 F) and the highest, 36 C (97 F), over the period covered was 8.9 mm (0.35 in.).
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 41-44
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  • 13
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    Remote intensity fluctuation measurements with a laser Doppler radar (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: A coaxial focused CW scanning laser Doppler velocimeter (SLDV) radar equipment applying heterodyne detection at 10.6 microns can measure intensity fluctuations under field conditions. The set includes a 20 W CO2 laser, a coaxial Cassegrainian telescope, standard heterodyne equipment, and a SAW spectrum analyzer with 100 kHz signal resolution. Operation of the equipment and techniques for taking remote measurements are described briefly. Applications to remote measurements of transverse component of wind speed, as a complement to the traditional Doppler method of determining axial velocity, are under study. SLDV equipment has been used in detection, tracking, and measurements of atmospheric turbulence associated with aircraft wing-tip vortices or with dust devils, and in measurement of general atmospheric wind profiles.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Applied Optics; 15; Sept
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  • 14
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    New sidelobe envelopes for small aperture earth stations (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The advent of domestic satellite systems and technological improvements in both space and ground equipment makes the use of small aperture earth stations economically feasible and attractive for broadcast satellite applications. With increasing use of the orbit spectrum, there is some concern that broadcast satellite systems may not be able to obtain satisfactory allocations of this orbit-spectrum resource because of interference considerations. Specifically, interference calculations based on the present envelope result in comparatively large orbit spacings for broadcast satellites. Theoretical and experimental investigations of simple sidelobe suppression techniques, plus an analysis of experimental data on small aperture antennas, indicate that much better sidelobe performance can be obtained with a very small cost or performance penalty.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Broadcasting; BC-22; June 197
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  • 15
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    The input admittance of the rectangular cavity-backed slot antenna (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The input admittance of the rectangular cavity-backed slot antenna is investigated. The slot is assumed narrow so that the voltage distribution in its aperture is sinusoidal. Equations which represent the input admittance of this slot, backed by a rectangular cavity in which a single propagating wave is assumed to exist, are given. Calculations based on these representations are compared to available measured data. As the depth of the cavity increased the resonant frequency decreased and the bandwidth became narrower. Input admittance curves as a function of electrical slot length are also presented for several size cavities.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation; AP-24; May 1976
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  • 16
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    Power conservation for reflector antennas with truncated feed patterns (1976)
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    Publication Date: 2011-08-16
    Description: Reflector-antenna calculations using idealised truncated feed patterns can lead to incorrect values of total secondary radiated power. It is demonstrated that this discrepancy is due to the presence of higher-order spherical modes incident on the reflector. When a proper spherical-wave expansion of the incident field is used, in conjunction with the physical-optics technique, to determine the scattered field, the total power of the scattered field will equal the power radiated by the feed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Electronics Letters; 12; Mar. 18
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  • 17
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    Satellite communications at the Goddard Space Flight Center (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Starting with the 1960 Delta launch of the first Echo satellite, NASA's Goddard Space Flight Center (GSFC) became one of the pioneers in satellite communications. Attention is given to the project Syncom, the Applications Technology Satellite (ATS) program, the ATS-6 project, and current GSFC efforts. After the decision announced in January of 1973 that NASA would phase out of communications satellite programs, the communications effort at GSFC concentrates on the operation of ATS spacecraft in orbit, experiments in the 12- to 14 GHz frequency band, and advanced communications research.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Signal; 30; Mar. 197
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  • 18
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    Real-time video compression algorithm for Hadamard transform processing (1976)
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    Publication Date: 2011-08-16
    Description: A real-time digital video processor using Hadamard transform techniques to reduce video bandwidth is described. The processor can be programmed with different parameters to investigate various algorithms for bandwidth compression. The processor is also adaptive in that it can select different parameter sets to tradeoff spatial resolution for temporal resolution in the regions of the picture that are moving. Algorithms used in programming the system are described along with results achieved at various levels of compression. The algorithms relate to spatial compression, temporal compression, and the adaptive selection of parameter sets.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Electromagnetic Compatibility; EMC-18; Feb. 197
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  • 19
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    Frequencies above 10 GHz (1976)
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    Publication Date: 2011-08-17
    Description: The paper discusses some of the problems associated with extending the frequencies used by satellite communication services above 10 GHz. The principal propagation limitation above 10 GHz occurs when precipitation intercepts the earth-space propagation path and causes attenuation and depolarization of the transmitted signal. World attenuation statistics at 12 GHz for earth-space paths are discussed, revealing the effect of climate on attenuation properties. Space diversity is discussed as an effective means of overcoming precipitation-caused attenuation problems.
    Keywords: COMMUNICATIONS AND RADAR
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  • 20
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    Analysis of the radiation patterns of reflector antennas (1976)
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    Publication Date: 2011-08-16
    Description: The development and application of a numerical technique for rapid calculation of the far-field radiation patterns of a reflector antenna from either a measured or computed feed pattern are reported. The reflector is defined by the intersection of a cone with any surface of revolution or an offset sector of any surface of revolution. The feed is assumed to be linearly polarized and can have an arbitrary location. Both the copolarized and the cross-polarized reflector radiation patterns are computed. Calculations using the technique compare closely with measured radiation patterns of a waveguide-fed offset parabolic reflector. Unique features of this technique are freedom from restrictive feed assumptions and the numerical methods used in preparing the aperture-plane electric-field data for integration.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation; AP-24; Jan. 197
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  • 21
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    Power line anomalies as they affect the operation of a DSN station: Overview (1980)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The problem of providing a sufficiently stable and reliable power source for the equipment in a DSN station is addressed. The potential for the occurrence of damaging commercial power variations is considered with respect to the need for a more precise power source.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 110-113
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  • 22
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    Feasibility and cost study on VOIR SAR data transfer via a bent pipe link (1980)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: An INTELSAT/DOMSAT double hop bent pipe link for the Venus orbiting imaging radar synthetic aperture radar imaging data transfer from deep space stations 43 and 63 to the Jet Propulsion Laboratory was investigated. The cost for the bent pipe transfer was estimated and compared to that for the planned tape record/airfreight-the-tape transfer method.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 82-90
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  • 23
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    Concerning the feasibility of a real time SAR digital processor for VOIR low resolution imaging modes (1980)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The feasibility of real time digital processing of synthetic aperture radar data for Venus orbiting imaging radar low resolution modes was investigated. First, it is shown that range migration is not a problem for these modes. Then, under the assumption of no range migration, fast Fourier transform implementations for accomplishing both range and azimuth correlation in real time are shown to be feasible with current technology.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 72-81
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  • 24
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    Use of K sub A-band for radio metric determinations (1980)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The use of K sub A-band to alleviate the radio metric degradation caused by charged particles is discussed. Those aspects of radio metrics which are relevant to the possible future use of K sub A-band deep space to Earth and Earth to deep space links are reviewed. In particular the effects of the Earth ionosphere, troposphere, and solar plasma are examined. It is concluded that, from the standpoint of reducing the harmful effects of charged particles, the use of K sub A-band appears highly desirable. While stability will be a more serious design constraint at K sub A-band than it is at X-band (for example in the ground power amplifier and the spacecraft multiplier stages) this problem is amenable to a state of the art engineering solution.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 59-66
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  • 25
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    The Tidbinbilla interferometer (1980)
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    Publication Date: 2011-08-17
    Description: A proposal to operate a two element interferometer using the 64 m and 26 m antennas of the Tidbinbilla Deep Space Station is discussed. The instrument is to be operated as a correlation interferometer, the sine and cosine products being sampled once per second and recorded for later analysis. The receiver systems are currently under development. Preliminary measurements of the delay line and local oscillator systems and the site cables suggest that a phase stability to within about 1 deg should be achievable with temperature control of the receiver packages.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 6-8
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  • 26
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    Comparison of two leading uniform theories of edge diffraction with the exact uniform asymptotic solution (1980)
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    Publication Date: 2011-08-18
    Description: The diffraction of an arbitrary cylindrical wave by a half-plane has been treated by Rahmat-Samii and Mittra who used a spectral domain approach. In this paper, their exact solution for the total field is expressed in terms of a new integral representation. For large wave number k, two rigorous procedures are described for the exact uniform asymptotic expansion of the total field solution. The uniform expansions obtained are valid in the entire space, including transition regions around the shadow boundaries. The final results are compared with the formulations of two leading uniform theories of edge diffraction, namely, the uniform asymptotic theory and the uniform theory of diffraction. Some unique observations and conclusions are made in relating the two theories.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Radio Science; 15; Nov
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  • 27
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    A note on antenna models in a warm isotropic plasma (1980)
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    Publication Date: 2011-08-18
    Description: The electron-transparent and electron-reflecting models of antennas in a warm isotropic plasma are reexamined. It is shown that a purely electrical treatment of both the models without an explicit use of the boundary condition on electron velocity yields the same results as those previously obtained through an electromechanical treatment. The essential difference between the two models is that for the electron-reflecting model, fields are nonzero only in the exterior region, while for the electron-transparent model, they are nonzero both in the exterior and interior regions of the antenna. This distinction helps in clarifying some misconceptions about these models of antennas in warm isotropic plasma.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Radio Science; 15; Nov
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  • 28
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    FFT methods in signal processing of the coal interface detector radar (1980)
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    Publication Date: 2011-08-18
    Description: The FM radar for the coal interface detector, operating in the frequency band 2 to 4 GHz, is intended for the display of thicknesses between 2 cm and 20 cm. Because of such a short range, the thickness information is contained in the very few lowest spectral components of the output signal. To overcome this inconvenience, the Fourier series of the output signal was augmented to approximate a Fourier integral. This modification in the signal processing resulted in a higher spectral density, which in turn enabled an easier identification of the interface position in the laboratory. The orientation and spacing of the receiving and transmitting antennas is found to have an important influence on the system performance.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Alabama Univ. Res. Rept.: The 1980 NASA(ASEE Summer Fac. Fellowship Program; 18 p
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  • 29
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    Simulation of orbital radar images (1980)
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    Publication Date: 2011-08-18
    Description: The operating parameters for spaceborne synthetic aperture imaging radar systems was addressed in the cost effective manner by using simulation techniques. The use of airborne images, Seasat images, and computer simulation were the first computer simulation of spaceborne radar imagery was analyzed for system definition studies. Analysis of the simulation indicates that incidence angles as small as 30 are useful for general terrain geomorphologic analysis.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Radar Geol: An Assessment Rept. of the Radar Geol. Workshop; p 45-63
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  • 30
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    System analysis for millimeter-wave communication satellites (1980)
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    Publication Date: 2011-08-17
    Description: Research and development needs for millimeter-wave space communication systems are presented. Assumed propagation fade statistics are investigated along with high data rate diversity link and storage. The development of reliable ferrite switches, and high performance receivers and transmitters is discussed, in addition to improved tolerance of dish and lens fabrication for the antennas. The typical cost for using a simplex voice channel via a high capacity 40/50 GHz satellite is presented.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Microwave Journal; 23; Oct. 198
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  • 31
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    The performance of suppressed carrier receivers in a pulsed RFI environment (1980)
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    Publication Date: 2011-08-17
    Description: This paper investigates the tracking performance of a Costas loop in the presence of single and multiple in-band pulsed RFI signals and receiver additive noise. It is shown that the loop's tracking performance is very sensitive to the pulse durations of the RFI signals, as well as their repetition rates and peak powers relative to those of the desired signal. The presence of in-band RFI can affect the loop's tracking performance in basically three ways. 1) The loop tracks the composite phase of the RFI instead of the phase of the desired signal when the effective RFI power is greater than that of the signal. 2) When the effective RFI power is not sufficiently large to capture the loop, there still will exist static phase error biases which cause the loop to lock at a phase between that of the desired signal and the composite RFI. 3) There is an increase in the rms phase jitter over the nominal design. These latter two effects degrade the bit error probability performance of the receiver. More significantly, if the nominal loop bandwidth is not designed properly to account for the increase in jitter phenomenon, frequency cycle slipping may result.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Communications; COM-28; May 1980
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  • 32
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    NASA technology for large space antennas (1980)
    In:  CASI
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    Publication Date: 2017-10-02
    Description: Some leading concepts for deployable antennas are described and an assessment of the state of the art in deployable antennas is presented. The advanced sunflower precision antenna, the radial rib antenna and the maypole (hoop/column) antenna, the wrap rib antenna and the parabolic erectable truss antenna are covered. In addition, a discussion on the technology development program for two deployable antenna concepts that are responsive to the antenna mission requirements as defined in the NASA mission model is presented.
    Keywords: COMMUNICATIONS AND RADAR
    Type: AGARD Requirements, Design and Develop. of Large Space Antenna Struct.; 2 p
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    A 20-kW X-band uplink transmitter development (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The 20 kW X-band transmitter power amplifier and its related control and monitor cabinet are described. The circuitry for the monitoring and protection of various transmitter components is discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition; p 89-95
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  • 34
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    ORION S-band data acquisition for S-Y calibration (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Error sources in the Operational Radio Interferometry Observing Network (ORION) are addressed. Specifically, the performance of the S-band receiver and the optimum allocation of data volume between S- and X-band observations is studied. It is found that the requirements on the S-band receiver are not very stringent. The system temperature of the ORION S-band receiver has a very small effect on baseline determination accuracy. It is unwise to pay a high cost for an S-band receiver with a low system temperature; a system temperature as high as 240 K is tolerable. Only 20 to 40 percent of data volume is to be allocated to S-band observations for minimum baseline error. The error remains low over a rather wide range of data volume ratio. Hence precise allocation of the 14 pairs of the Mark 3 very long base interferometer data channels between S- and X-band observations is not critical.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 33-36
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  • 35
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    Radio frequency performance of DSS 14 64-meter antenna at X-band using an improved subreflector (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The performance of the Deep Space Station (DSS) 14 64-meter antenna X-band gain determined using the X- and K-band Radar feedcone is discussed. Tests prior to, and following the installation of an improved subreflector, proved the unit largely (if not totally) restored initial performance levels at that station. The X-band peak gain with the subreflector is +17.8dBi(area efficiency of 47.3 percent); an increase of +0.47 dB due to the unit installation. The test further showed a significant shift in the axial focus required (function of elevation angle) which, if not implemented operationally, will cause a serious degradation. An historical summary of all documented X-band gain measurements at DSS 14 is included and reviewed. The initial performance is traced through various major configuration changes such as the installation of the X-band dual hybrid mode horn within the operational XRO feedcone. Finally, based on the summary and recent data, a peak X-band antenna gain of +72.1 dBi (area efficiency of 50.8 percent) is projected for the operational feedcone.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition; p 168-176
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  • 36
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    RFI channels (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A class of channel models is presented which exhibit varying burst error severity much like channels encountered in practice. An information-theoretic analysis of these channel models is made, and conclusions are drawn that may aid in the design of coded communication systems for realistic noisy channels.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition; p 103-106
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  • 37
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    Planetary radar (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The radar astronomy activities supported by the Deep Space Network during June, July, and August 1980 are reported. The planetary bodies observed were Venus, Mercury, and the asteroid Toro. Data were obtained at both S and X band, and the observations were considered successful.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 142-144
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  • 38
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    Open-loop radio science with a suppressed-carrier signal (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: When a suppressed-carrier signal is squared, the carrier reappears in doubled form. An open-loop receiver can be used to deliver a recording of a band-limited waveform containing this carrier, whose amplitude and phase can be tracked by the radio science experimenter.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 86-97
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  • 39
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    Goldstone radio spectrum protection (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Potential electromagnetic interference to the Goldstone tracking receivers due to neighboring military installations is discussed. Coordination of the military and NASA Goldstone activities in the Mojave Desert area is seen to be an effective method to protect the Goldstone radio spectrum while maintaining compatible operations for the military and Goldstone.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition; p 177-182
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  • 40
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    Prototype real-time baseband signal combiner (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The design and performance of a prototype real-time baseband signal combiner, used to enhance the received Voyager 2 spacecraft signals during the Jupiter flyby, is described. Hardware delay paths, operating programs, and firmware are discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition; p 145-151
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  • 41
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    DSN Ground Communications Facility (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A functional description of the Ground Communications Facility (GCF) and its relationships with other elements of the Deep Space Network and the NASA Communications Network is presented together with development objectives and goals and comments on implementation activities in support of flight projects. The voice, teletype, high speed data, wideband data, monitor and control, data records, network log processor, and network communications equipment subsystems are individually examined.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 40-50
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  • 42
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    Utilization of the Venus Station (DSS 13) 26 meter antenna during CY 1979 (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The various activities for which the Venus Station's 26 m antenna was used are described and the number of manned tracking hours devoted to each activity are given. A brief description of the goal of each activity supported is provided, and, where appropriate, the observing technique is summarized. Projects involving spacecraft tracking, advanced systems development, and radio astronomy are included.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 136
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  • 43
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    DSN command system Mark III-80 (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The Deep Space Network command system configuration and functional operation are described. Voyager and Helios command operations are supported with Deep Space Station store and forward data handling; Viking and Pioneer are supported with the older, near real time data handling method.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 35-42
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  • 44
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    The 64 meter antenna operation at K sub A band (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The future potential of the 32 GHz K sub A band frequency region to planetary exploration, and the expected performance of the 64 m antenna network at 32 GHz is addressed. A modest level of noninterference upgrade work is assumed to achieve reasonable antenna aperture efficiency and alleviate antenna pointing difficulties. Electronic compensation of antenna aperture phasing errors is briefly considered as an alternative to the physical upgrade.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 65-70
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  • 45
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    The SETI observational plan (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The SETI (Search for Extraterrestrial Intelligence) Project's primary thrust is to search the microwave region of the spectrum for signals of extraterrestrial intelligent origin. The project will search a well defined volume of search parameter space using existing antennae and a sophisticated data acquisition and analysis system. Two major components are included, the target survey, which will observe at very high sensitivity all attractive stellar candidates within 75 light years of the Sun, and the sky survey, which will observe the entire celestial sphere at a lower sensitivity.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept. p43-49 (SEE N80-26341 17-12)
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  • 46
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    RFI receiver (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: An S-band radio frequency interference (RFI) receiver to analyze and identify sources of RFI problems in the Deep Space Network DSN tracking stations is described. The RFI receiver is a constant gain, double conversion, open loop receiver with dual sine/cosine channel outputs, providing a total of 20 MHZ monitoring capability. This receiver is computer controlled using a MODCOMP II miniprocessor. The RFI receiver has been designed to operate at a 150 Kelvin system noise temperature accomplished by cascading two low noise field effect transistor (FET) amplifiers for the receiver front-end. The first stage low noise FET amplifier is mounted at the feed horn to minimize any cable losses to achieve a lower system noise temperature. The receiver is tunable over the frequency range of 2150 to 2450 MHz in both sine/cosine output channels with a resolution of 100 kHz.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 82-86
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  • 47
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    Error estimation for ORION baseline vector determination (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Effects of error sources on Operational Radio Interferometry Observing Network (ORION) baseline vector determination are studied. Partial derivatives of delay observations with respect to each error source are formulated. Covariance analysis is performed to estimate the contribution of each error source to baseline vector error. System design parameters such as antenna sizes, system temperatures and provision for dual frequency operation are discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 16-31
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  • 48
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    Block 4 receiver tracking loop performance in the presence of a CW RFI (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A model that allows one to predict the tracking performance of the Block 4 receiver in the presence of a continuous wave radio frequency interference is discussed. Experimental and analytical results are provided for a typical Deep Space Network operational mode. Simulation and experimental results show good agreement with theoretical prediction for the static phase error and out-of-lock values. Predicted phase jitter is consistently lower than the experimental and simulated results by a factor of one-half for small interference to signal ratio (ISR) when the offset frequency is small. For large ISR, good agreement is observed. The analytical model assumes a noiseless condition, which is valid only when the loop is operated at strong signal levels. Experimental data indicate, however, that even at the minimum operating signal level of 10-dB carrier margin, reasonably good prediction can still be obtained. A curve of protection criteria that extends the current recommendation is also presented.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition; p 155-167
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  • 49
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    RFI prevention for colocated antennas (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Potential radio frequency interference problems related to the colocation of antennas for the Mark 4-A Deep Space network are analyzed. Cases discussed include effects of S-band uplinks on X-band downlinks and S-band downlinks, planetary radar at Goldstone, future X-band uplink, radiometer measurements, Search for Extraterrestrial Intelligence instrument, and radio astronomy projects. Remedial actions are suggested.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition; p 135-144
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  • 50
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    Interleaved block codes for the photon channel (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: It is shown that interleavel binary block codes combined with pulse position modulation give the best practical coded systems yet devised for optical communication with photon detection. Linear block codes rather than convolutional codes are considered.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition; p 98-102
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  • 51
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    Capacity, cutoff rate, and coding for a direct-detection optical channel (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: It is shown that Pierce's pulse position modulation scheme with 2 to the L pulse positions used on a self-noise-limited direct detection optical communication channel results in a 2 to the L-ary erasure channel that is equivalent to the parallel combination of L completely correlated binary erasure channels. The capacity of the full channel is the sum of the capacities of the component channels, but the cutoff rate of the full channel is shown to be much smaller than the sum of the cutoff rates. An interpretation of the cutoff rate is given that suggests a complexity advantage in coding separately on the component channels. It is shown that if short-constraint-length convolutional codes with Viterbi decoders are used on the component channels, then the performance and complexity compare favorably with the Reed-Solomon coding system proposed by McEliece for the full channel. The reasons for this unexpectedly fine performance by the convolutional code system are explored in detail, as are various facets of the channel structure.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition; p 68-76
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  • 52
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    Experimental optical fiber communications link (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: An optical fiber communications link 1.5 kilometers in length was installed between the Interim Frequency Standard Test Facility and the Timing and Frequency Systems Research Laboratory at JPL. It is being used to develop optical fiber technology for use in the DSN and particularly for precise time and frequency distribution.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 77-85
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  • 53
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    Pattern measurements of a low-sidelobe horn antenna (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The techniques and results of power pattern measurements of a corrugated horn antenna designed for low sidelobes are reported. The power pattern was measured to levels 90 dB below the main beam maximum in both the E- and H-planes. The measured patterns were found to be in good agreement with predictions from existing theory for the performance of corrugated scalar feeds.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 8-14
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  • 54
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    GPS/REFSAT definition study report for low-cost terminals (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A relay transponder, located either on a satellite in geostationary orbit or on a local tower to relay acquisition-aiding data, ephemerides, etc, from a ground-based remote control station to a GPS civil user terminal located on a ship or land-transportation vehicle is described. Termed REFSAT (Reference Satellite), this concept reduces the circuit complexity and cost of user terminals. The various systems needed to implement the REFSAT concept for low-cost, GPS civil terminals are defined. The GPS/REFSAT system compatible with the NAVSTAR GPS system consists of a geostationary relay satellite, civil user terminals, and the central facility which performs operations common to all users for relay via the space segment. A GPS/REFSAT system utilizing a local tower for the relay transponder is described, results of a study of civil user requirements are presented, and specifications for the GPS/REFSAT system and its individual segments are included.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-166696
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  • 55
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    A study of radio frequency interference with the Nimbus-7 Scanning Multichannel Microwave Radiometer (SMMR) (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: One of the important objectives of the NIMBUS-7 Scanning Multichannel Microwave Radiometer (SMMR) is to demonstrate the feasibility of all weather measurements of various ocean parameters; such as sea surface temperature (SST) and near surface wind speed (WS). These ocean parameters can be determined from multispectral measurements of ocean brightness temperatures in the microwave region of the electromagnetic spectrum. These microwave measurements, however, are distorted if the field of view of the SMMR antenna encounters radio transmissions from terrestrial sources. Sources of terrestrial Radio Frequency Interference (RFI) in the SMMR ocean data were identified. Its extent and characteristics over different ocean areas on the Earth were determined.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-166638
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  • 56
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    A prototype DSN X/S-band feed: DSS 13 application status (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A prototype X/S-band common aperture horn feed for future use at various DSN sites and the Network Consolidation Program is discussed. The final design and fabrication of the second generation feedhorn and combiner is dealt with. The results of the measurements obtained with the second generation, full scale feed configuration are presented.
    Keywords: COMMUNICATIONS AND RADAR
    Type: REPT-4 , The Telecommun. and Data Acquisition; P 77-88
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  • 57
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    Multi-mode horn antenna simulation (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Radiation patterns were computed for a circular multimode horn antenna using waveguide electric field radiation expressions. The circular multimode horn was considered as a possible reflector feed antenna for the Large Antenna Multifrequency Microwave Radiometer (LAMMR). This horn antenna uses a summation of the TE sub 11 deg and TM sub 11 deg modes to generate far field primary radiation patterns with equal E and H plane beamwidths and low sidelobes. A computer program for the radiation field expressions using the summation of waveguide radiation modes is described. The sensitivity of the multimode horn antenna radiation patterns to phase variations between the two modes is given. Sample radiation pattern calculations for a reflector feed horn for LAMMR are shown. The multimode horn antenna provides a low noise feed suitable for radiometric applications.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-80705
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  • 58
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    Vector analogues of the Maggi-Rubinowicz theory of edge diffraction (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The Maggi-Rubinowicz technique for scalar and electromagnetic fields is interpreted as a transformation of an integral over an open surface to a line integral around its rim. Maggi-Rubinowicz analogues are found for several vector physical optics representations. For diffraction from a circular aperture, a numerical comparison between these formulations shows the two methods are in agreement. To circumvent certain convergence difficulties in the Maggi-Rubinowicz integrals that occur as the observer approaches the shadow boundary, a variable mesh integration is used. For the examples considered, where the ratio of the aperture diameter to wavelength is about ten, the Maggi-Rubinowicz formulation yields an 8 to 10 fold decrease in computation time relative to the physical optics formulation.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-82024
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  • 59
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    An analysis of short pulse and dual frequency radar techniques for measuring ocean wave spectra from satellites (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Scanning beam microwave radars were used to measure ocean wave directional spectra from satellites. In principle, surface wave spectral resolution in wave number can be obtained using either short pulse (SP) or dual frequency (DF) techniques; in either case, directional resolution obtains naturally as a consequence of a Bragg-like wave front matching. A four frequency moment characterization of backscatter from the near vertical using physical optics in the high frequency limit was applied to an analysis of the SP and DF measurement techniques. The intrinsic electromagnetic modulation spectrum was to the first order in wave steepness proportional to the large wave directional slope spectrum. Harmonic distortion was small and was a minimum near 10 deg incidence. NonGaussian wave statistics can have an effect comparable to that in the second order of scattering from a normally distributed sea surface. The SP technique is superior to the DF technique in terms of measurement signal to noise ratio and contrast ratio.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-82011
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  • 60
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    Pilot signals for large active retrodirective arrays (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: It was suggested that for large active retrodirective arrays, as in the solar power system, a two tone uplink pilot signal with frequencies symmetrically situated around the downlink frequency be used in order to reduce ionospheric biases and to lower the cost. Unfortunately such a system faces the following difficulties: (1) the pi-ambiguity, and (2) a large phase difference between the downlink and uplink signals. It is shown how the pi-ambiguity can be easily removed by using a two tone uplink signal with both frequencies situated at one side of the downlink frequency, and the phase difference can be greatly reduced with a three tone or a four tone uplink pilot signal.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Res. Rept.: The 1980 NASA(ASEE Summer Fac. Fellowship Program; 17 p
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  • 61
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    KU-Band rendezvous radar performance computer simulation model (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The preparation of a real time computer simulation model of the KU band rendezvous radar to be integrated into the shuttle mission simulator (SMS), the shuttle engineering simulator (SES), and the shuttle avionics integration laboratory (SAIL) simulator is described. To meet crew training requirements a radar tracking performance model, and a target modeling method were developed. The parent simulation/radar simulation interface requirements, and the method selected to model target scattering properties, including an application of this method to the SPAS spacecraft are described. The radar search and acquisition mode performance model and the radar track mode signal processor model are examined and analyzed. The angle, angle rate, range, and range rate tracking loops are also discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-160883
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  • 62
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    Automatic shading correction and speckle noise mapping/removal techniques for radar image data (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Techniques were developed to correct for shading problems, and to suppress speckle noise contained in the radar images.
    Keywords: COMMUNICATIONS AND RADAR
    Type: JPL Radar Geol.: An Assessment Rept. of the Radar Geol. Workshop; p 251-262
    Format: text
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  • 63
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    Radar estimation of slant path rain attenuation at frequencies above 10 GHz and comparisons with measured multi-season results (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Techniques and results pertaining to estimating Earth satellite path rain attenuation events and statistics using radar at nonattenuating wavelengths are presented. The radar formulation and beam scanning methods are described and the procedure for relating the radar measured Rayleigh reflectivity to the high frequency Mie attenuation coefficient are given. Examples of radar derived single terminal statistics and estimation criteria as they relate to path angle and frequency are reviewed. Radar derived space diversity statistics and their dependence on terminal spacing and frequency are described. Site diversity performance curves obtained by radar and radiometry are compared with each other demonstrating the utility of radar methods. Results of a multi-year experiment to test, refine, and establish accuracies of radar methods for arriving at estimates of rain attenuation along an Earth-satellite path are discussed. Comparisons of measured and radar estimated fade events are presented and found to be good. Comparisons of cumulative fade distributions show agreement to be excellent giving an rms deviation of 1 dB.
    Keywords: COMMUNICATIONS AND RADAR
    Type: AGARD Propagation Effects in Space(Earth Paths; 12 p
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  • 64
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    Second year technical report on-board processing for future satellite communications systems (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Advanced baseband and microwave switching techniques for large domestic communications satellites operating in the 30/20 GHz frequency bands are discussed. The nominal baseband processor throughput is one million packets per second (1.6 Gb/s) from one thousand T1 carrier rate customer premises terminals. A frequency reuse factor of sixteen is assumed by using 16 spot antenna beams with the same 100 MHz bandwidth per beam and a modulation with a one b/s per Hz bandwidth efficiency. Eight of the beams are fixed on major metropolitan areas and eight are scanning beams which periodically cover the remainder of the U.S. under dynamic control. User signals are regenerated (demodulated/remodulated) and message packages are reformatted on board. Frequency division multiple access and time division multiplex are employed on the uplinks and downlinks, respectively, for terminals within the coverage area and dwell interval of a scanning beam. Link establishment and packet routing protocols are defined. Also described is a detailed design of a separate 100 x 100 microwave switch capable of handling nonregenerated signals occupying the remaining 2.4 GHz bandwidth with 60 dB of isolation, at an estimated weight and power consumption of approximately 400 kg and 100 W, respectively.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-165155 , MTR-8164 , TR-2
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  • 65
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    Pilot signals for large active retro-directive arrays (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: It has been suggested that for large active retrodirective arrays, as in the solar power system, a two tone uplink pilot signal with frequencies symmetrically situated around the downlink frequency be used in order to reduce ionospheric biases and to lower the cost since a two tone receiver is economically much cheaper than a single tone phase locked receiver. Such a system now faces two difficulties: the Pi-ambiguity; and a large phase difference between the downlink and uplink signals. The Pi-ambiguity is shown to be easily removed by using a two tone uplink signal with both frequencies situated at one side of the downlink frequency, and the phase difference can be greatly reduced with a three tone or a four tone uplink pilot signal.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-78310
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    Some important geometrical features of conic-section-generated offset reflector antennas (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Geometrical characteristics of conic-section-generated offset reflectors are studied in a unified fashion. Some unique geometrical features of the reflector rim constructed from the intersection of the reflector surface and a cone or cylinder are explored in detail. It is found that the intersection curve (rim) of the rotationally generated conic-section reflector surface and a circular cone with its tip at the focal point is always a planar curve and has a circular projection on the focal plane only for the offset parabolic reflector. Furthermore, in this case, the line going through the center of the circle, parallel to the focal axis, and the central axis of the cone do not intersect the reflector surface at the same point. Numerical results are presented to demonstrate some unique features of offset parabolic reflectors.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation; AP-28; Nov. 198
    Format: text
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  • 67
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    CTS/Comstar communications link characterization experiment (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Measurements of angle of arrival and amplitude fluctuations on millimeter wavelength Earth-space communication links are described. Measurement of rainfall attenuation and radiometric temperature statistics and the assessment of the performance of a self-phased array as a receive antenna on an Earth-space link are also included.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-166648 , ESL-784299-9
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    Evaluation of the effects of varying moisture contents on microwave thermal emissions from agriculture fields (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Three tasks related to soil moisture sensing at microwave wavelengths were undertaken: (1) analysis of data at L, X and K sub 21 band wavelengths over bare and vegetated fields from the 1975 NASA sponsored flight experiment over Phoenix, Arizona; (2) modeling of vegetation canopy at microwave wavelengths taking into consideration both absorption and volume scattering effects; and (3) investigation of overall atmospheric effects at microwave wavelengths that can affect soil moisture retrieval. Data for both bare and vegetated fields are found to agree well with theoretical estimates. It is observed that the retrieval of surface and near surface soil moisture information is feasible through multi-spectral and multi-temporal analysis. It is also established that at long wavelengths, which are optimal for surface sensing, atmospheric effects are generally minimal. At shorter wavelengths, which are optimal for atmosheric retrieval, the background surface properties are also established.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-166679 , ERT-P-A245
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  • 69
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    The 30/20 Gigahertz transponder study (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Design features and performance parameters are described for three types of wideband multiple channel satellite transponders for use in a 30/20 GHz communications satellite, which provides high data rate trunking service to ten ground station terminals. The three types of transponder are frequency division multiplex (FDM), time division multiplex (TDM), and a hybrid transponder using a combination of FDM and TDM techniques. The wideband multiple beam trunking concept, the traffic distribution between the trunking terminals, and system design constraints are discussed. The receiver front end design, the frequency conversion scheme, and the local oscillator design are described including the thermal interface between the transponders and the satellite. The three designs are compared with regard to performance, weight, power, cost and initial technology. Simplified block diagrams of the baseline transponder designs are included.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-165295
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    Ku-band multiple beam antenna (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The frequency reuse capability is demonstrated for a Ku-band multiple beam antenna which provides contiguous low sidelobe spot beams for point-to-point communications between any two points within the continental United States (CONUS), or regional coverage beams for direct broadcast systems. A spot beam antenna in the 14/21 GHz band which provides contiguous overlapping beams covering CONUS and two discrete beams covering Hawaii and Alaska were designed, developed, and tested. Two reflector antennas are required for providing contiguous coverage of CONUS. Each is comprised of one offset parabolic reflector, one flat polarization diplexer, and two separate planar array feeds. This antenna system provides contiguous spot beam coverage of CONUS, utilizing 15 beams. Also designed, developed and demonstrated was a shaped contoured beam antenna system which provides contiguous four time zone coverage of CONUS from a single offset parabolic reflector incorporating one flat polarization diplexer and two separate planar array feeds. The beams which illuminate the eastern time zone and the mountain time zone are horizontally polarized, while the beams which illuminate the central time zone and the pacific time zone are vertically polarized. Frequency reuse is achieved by amplitude and polarization isolation.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-159364
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  • 71
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    Support assembly for cryogenically coolable low-noise choke waveguide (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A compact cryogenically coolable choked waveguide for low-noise input coupling into a cryogenically cooled device, such as a maser or parametric amplifier, utilizes coaxial stainless steel support tubes surrounding the waveguide and connected in cascade to provide a folded low thermal conduction path. The edges of the tubes connected are welded.
    Keywords: COMMUNICATIONS AND RADAR
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  • 72
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    Video distribution system cost model (1980)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: A cost model that can be used to systematically identify the costs of procuring and operating satellite linked communications systems is described. The user defines a network configuration by specifying the location of each participating site, the interconnection requirements, and the transmission paths available for the uplink (studio to satellite), downlink (satellite to audience), and voice talkback (between audience and studio) segments of the network. The model uses this information to calculate the least expensive signal distribution path for each participating site. Cost estimates are broken downy by capital, installation, lease, operations and maintenance. The design of the model permits flexibility in specifying network and cost structure.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-160020 , PUBL-1358-01-3-2238
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  • 73
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    A simple stripline design for uneven power split (1980)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: A technique for the design of stripline or microstrip power dividers for unequal, but in-phase, power split is described. The output power ratio is determined by selecting the location of the input port in a manner analogous to the tap point for an electric power transformer. The technique yields a usable bandwidth of 7 to 8 percent and is attractive for tapered amplitude distribution networks for narrow band phased arrays.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-81870
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  • 74
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    A study of a space communication system for the control and monitoring of the electric distribution system. Volume 2: Supporting data and analyses (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: It is technically feasible to design a satellite communication system to serve the United States electric utility industry's needs relative to load management, real-time operations management, remote meter reading and to determine the costs of various elements of the system. The functions associated with distribution automation and control and communication system requirements are defined. Factors related to formulating viable communication concepts, the relationship of various design factors to utility operating practices, and the results of the cost analysis are discussed The system concept and several ways in which the concept could be integrated into the utility industry are described.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-163478 , JPL-PUB-80-48-VOL-2
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  • 75
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    An assessment of inductive coupling roadway powered vehicles (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The technical concept underlying the roadway powered vehicle system is the combination of an electrical power source embedded in the roadway and a vehicle-mounted power pickup that is inductively coupled to the roadway power source. The feasibility of such a system, implemented on a large scale was investigated. Factors considered included current and potential transportation modes and requirements, economics, energy, technology, social and institutional issues. These factors interrelate in highly complex ways, and a firm understanding of each of them does not yet exist. The study therefore was structured to manipulate known data in equally complex ways to produce a schema of options and useful questions that can form a basis for further, harder research. A dialectical inquiry technique was used in which two adversary teams, mediated by a third-party team, debated each factor and its interrelationship with the whole of the known information on the topic.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-163437 , JPL-PUB-79-115
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  • 76
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    Beamed microwave power transmitting and receiving subsystems radiation characteristics (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Measured characteristics of the spectrum of typical converters and the distribution of radiated Radio Frequency (RF) energy from the terminals (transmitting antenna and rectenna) of a beamed microwave power subsystem are presented for small transmitting and receiving S-band (2.45 GHz) subarrays. Noise and harmonic levels of tube and solid-state RF power amplifiers are shown. The RF patterns and envelope of a 64 element slotted waveguide antenna are given for the fundamental frequency and harmonics through the fifth. Reflected fundamental and harmonic patterns through the fourth for a 42 element rectenna subarray are presented for various dc load and illumination conditions. Bandwidth measurements for the waveguide antenna and rectenna are shown.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-163362 , JPL-PUB-80-11
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  • 77
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    Focal axis resolver for offset reflector antennas (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Described are electrical means for determining the focal axis of an offset reflector antenna whose physical rim is not coincident with the boundary of the electrical aperture. Even and odd sensing functions are employed in the focal region, leading to both amplitude and phase criteria for resolving a focal axis generally inclined with respect to the system axis. The analytical aspects of the problem are discussed, and an example related to a 4-meter Large-Antenna Multiple-Frequency Microwave Radiometer (LAMMR) is included. The technique is useful for focal axis determination in mathematical simulations and in the physical world.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-80683
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  • 78
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    Ultramicrowave communications system, phase 2 (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Communications system design was completed and reviewed. Minor changes were made in order to make it more cost effective and to increase design flexibility. System design activities identified the techniques and procedures to generate and monitor high data rate test signals. Differential bi-phase demodulation is the proposed method for this system. The mockup and packaging designs were performed, and component layout and interconnection constraints were determined, as well as design drawings for dummy parts of the system. The possibility of adding a low cost option to the transceiver system was studied. The communications program has the advantage that new technology signal processing devices can be readily interfaced with the existing radio frequency subsystem to produce a short range radar.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-160573 , MDC-E2209
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  • 79
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    Comparison of radar derived slant path rain attenuations with the COMSTAR beacon fades at 28.56 GHz for summer and winter periods (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: An experiment for testing and improving the accuracy of radar derived slant path attenuations of a 28.56-GHz COMSTAR beacon signal is described. The results of an additional data base consisting of five rain days during fall-winter periods of 1978-1979 are considered, over which 715 min of simultaneous radar and disdrometer data were obtained.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation; AP-28; July 198
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  • 80
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    Shuttle orbiter Ku-band radar/communications system design evaluation. Deliverable test equipment evaluation (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The Ku-band test equipment, known as the Deliverable System Test equipment (DSTE), is reviewed and evaluated. The DSTE is semiautomated and computer programs were generated for 14 communication mode tests and 17 radar mode tests. The 31 test modules provide a good cross section of tests with which to exercise the Ku-band system; however, it is very limited when being used to verify Ku-band system performance. More detailed test descriptions are needed, and a major area of concern is the DSTE sell-off procedure which is inadequate.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-160761 , R8007-5 , NAS 1.26:160761
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  • 81
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    Scannable beam forming interferometer antenna array system (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: An antenna array is described which comprises three interferometer pairs of antenna elements with selected spacings made to form a single beam which is readily scannable. All spatial frequencies generated by a signal and intercepted by the array are derived from a signal processing technique applied to the array. The array samples space in the spatial frequency domain while the signal processing technique utilizes real time convolution of functions in the spectral frequency domain. Summation of the appropriate spatial frequencies is equilvalent to a Fourier transform operation, yielding the location of the signal source in space. Resolution and freedom from interference of the interferometer system is equal to that of a fully filled array of the same aperture size containing element spacings of one half wavelength. An antenna array system comprising four antenna elements forming six interferometer pairs with a resolution equal to that of a sixteen element array with spacings of one half wavelength is described, as well as other multiples of one quarter wavelength of partial multiples of a wave length.
    Keywords: COMMUNICATIONS AND RADAR
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  • 82
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    Dual band combiner for horn antenna (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A corrugated horn antenna, adapted to be coupled to a waveguide at its apex for X-band excitation is further adapted to be connected to waveguides through a circumferential slot for S-band excitation at four distinct phases selected for the desired S-band polarization. The circumferential slot is positioned along the axial length of the horn for good impedance matching and is provided with an X-band choke in the form of two concentric choke slots. For further improvement in impedance matching, the second (outer) choke slot is divided by plugs into four segments that coincide with waveguide ports for the four distinct phases of the S-band.
    Keywords: COMMUNICATIONS AND RADAR
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  • 83
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    An advanced domestic satellite communications system (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: An updated traffic projection for U.S. domestic satellite communications service covering a period of 15 years; mid-1980 to mid-1995 was prepared. This model takes into account expected technology advances and reductions in transmission costs, legislative and regulatory changes permitting increased competition, and rising energy costs which will encourage more extensive substitution of telecommunications for travel. The historical development and current status of satellite systems are discussed as well as the characteristics of follow-on systems. Orbital arc utilization, spacecraft configuration for single shuttle launch, Earth station configuration, and system costs are examined. Areas which require technology development include multiple beam frequency reuse antennas, on-board switching, intersatellite links, and ka-band operation. Packing and deployment schemes for enclosing the satellite within the shuttle orbiter bay must also be devised.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-163004 , FSI-242
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  • 84
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    Electromagnetic backscattering from a random distribution of lossy dielectric scatterers (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Electromagnetic backscattering from a sparse distribution of discrete lossy dielectric scatterers occupying a region 5 was studied. The scatterers are assumed to have random position and orientation. Scattered fields are calculated by first finding the mean field and then by using it to define an equivalent medium within the volume 5. The scatterers are then viewed as being embedded in the equivalent medium; the distorted Born approximation is then used to find the scattered fields. This technique represents an improvement over the standard Born approximation since it takes into account the attenuation of the incident and scattered waves in the equivalent medium. The method is used to model a leaf canopy when the leaves are modeled by lossy dielectric discs.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-162922
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    The relationship of storm severity to directionally resolved radio emissions (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Directionally resolved atmospheric radio frequency emission data were acquired from thunderstorms occurring in the central and southwestern United States. In addition, RF sferic tracking data were obtained from hurricanes and tropical depressions occurring in the Gulf of Mexico. The data were acquired using a crossed baseline phase interferometer operating at a frequency of 2.001 MHz. The received atmospherics were tested for phase linearity across the array, and azimuth/elevation angles of arrival were computed in real time. A histogram analysis of sferic burst count versus azimuth provided lines of bearing to centers of intense electrical activity. Analysis indicates a consistent capability of the phase linear direction finder to detect severe meteorological activity to distances of 2000 km from the receiving site. The technique evidences the ability to discriminate severe storms from nonsevere storms coexistent in large regional scale thunderstorm activity.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-161381
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  • 86
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    Satellite personal communications system (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Voice channel communication between low power mobile stations dispersed over a large area is provided by a system which includes a geostationary satellite utilizing a large UHF antenna that can receive a transmission from a caller and retransmit it over any one beam of a matrix of narrow beams, so the chosen beam covers an area in which a designated called party is located. A single up-link control channel occupying a narrow frequency band, can be utilized to receive dial up signals from a caller, and another single down link control channel can be utilized to ring up the called party located anywhere within the continental United States. The satellite antenna includes a matrix of feed horns that not only direct the beams in a controlled matrix onto the area of the continental United States, but also permit detection of the region from which the caller's signal is transmitted and the region from which the called party's answer is received, to enable the interconnection of signals received from these two regions. The system is particularly useful for rural areas.
    Keywords: COMMUNICATIONS AND RADAR
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  • 87
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    Optical-communication systems for deep-space applications (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The feasibility of using optical communication systems for data telemetry from deep space vehicles to Earth based receivers is evaluated. Performance analysis shows that practical, photon counting optical systems can transmit data reliably at 30 to 40 dB high rates than existing RF systems, or can be used to extend the communication range by 15 to 20 dB. The advantages of pulse-position modulation (PPM) formats are discussed, and photon counting receiver structures designed for PPM decoding are described. The effects of background interference and weather on receiver performance are evaluated. Some consideration is given to tracking and beam pointing operations, since system performance ultimately depends on the accuracy to which these operations can be carried out. An example of a tracking and pointing system utilizing an optical uplink beacon is presented, and it is shown that microradian beam pointing is within the capabilities of state-of-the-art technology. Recommendations for future theoretical studies and component development programs are presented.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-162882 , JPL-PUB-80-7
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  • 88
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    The geometry of the 37-tile microwave antenna support structure (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The geometry of the support structure for a proposed parabolic shaped microwave antenna is examined. The surface of the antenna is comprised of 37 hexagonal shaped tiles, each connected to a truss module. The units are joined together to form a rigidized, faceted, concave parabolic surface. The geometry specifications are described through an explanation of the structural components which make up the antenna, a description of the coordinate system devised to identify the structure, and a presentation of the nondimensional results.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-162847 , ARC-TN-1083
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  • 89
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    Radio frequency arraying method for receivers (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A method and apparatus for increasing the signal to noise ratio of a receiving facility for coherent frequency reception by arraying receiving systems using separate antennas for each, or one antenna for all systems are presented. One system is operated with a carrier tracking loop to provide a first local oscillator frequency for the first and all other systems arrayed, with individual tracking loops in all other systems operated at IF for tracking out any phase differences due to separate group delays using an adjustable phase shifter for a second reference to compensate for different group delays in the antenna and low noise amplifier of each of the other systems. The second IF output of all systems is summed into the first system. This technique may also be used when two systems are arrayed to an antenna designed for circular or linear polarization diversity reception to effectively provide the same signal to noise ratio for both polarized signal transmission channels that would result from matched polarization. An arrangement adapted to high rate telemetry reception is disclosed. With additional components, the same arrangement is adapted to provide low rate telemetry reception as well.
    Keywords: COMMUNICATIONS AND RADAR
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  • 90
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    High-speed data link for moderate distances and noisy environments (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A full duplex, high speed data link is described which comprises identical modules at each site for communication over coaxial cables. Each module having a digital frequency modulation (DFM) transmitter with an first-in-first-out (FIFO) data buffer for data from a digital system to be transmitted over a cable and a receiver with an FIFO data buffer for data received for a digital system at the other end of the cable. Data words are preceded by a sync word which enables the receiver. Every word transmitted, including the sync word is stored in the FIFO data buffer. This arrangement using FIFO buffers allows for asynchronous transmission of data with receipt of the data beginning with the very first bit of the sync word.
    Keywords: COMMUNICATIONS AND RADAR
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  • 91
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    Alternate symbol inversion for improved symbol synchronization in convolutionally coded systems (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Inverting alternate symbols of the encoder output of a convolutionally coded system provides sufficient density of symbol transitions to guarantee adequate symbol synchronizer performance, a guarantee otherwise lacking. Although alternate symbol inversion may increase or decrease the average transition density, depending on the data source model, it produces a maximum number of contiguous symbols without transition for a particular class of convolutional codes, independent of the data source model. Further, this maximum is sufficiently small to guarantee acceptable symbol synchronizer performance for typical applications. Subsequent inversion of alternate detected symbols permits proper decoding.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Communications; COM-28; Feb. 198
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  • 92
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    Spectral characteristics of convolutionally coded digital signals (1980)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The power spectral density of the output symbol sequence of a convolutional encoder is computed for two different input symbol stream source models, namely, an NRZ signaling format and a first-order Markov source. The effects of alternate symbol inversion on this spectrum are also considered. The mathematical results are illustrated with many examples corresponding to optimal performance codes. It is demonstrated that only for the case of a purely random input source (e.g., NRZ data with equiprobable symbols) and a particular class of codes is the output spectrum identical to the input spectrum except for a frequency scaling (expansion) by the reciprocal of the code rate.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Communications; COM-28; Feb. 198
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  • 93
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    A parametric analysis of performance characteristics of satellite-borne multiple-beam antennas (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: An analytical and empirical model is presented for parametric study of multiple beam antenna frequency reuse capacity and interbeam isolation. Two types of reflector antennas, the axisymmetric parabolic and the offset-parabolic reflectors, are utilized to demonstrate the model. The parameters of the model are introduced and their limitations are discussed in the context of parabolic reflector antennas. The model, however, is not restricted to analysis of reflector antenna performance. Results of the analyses are covered in two tables. The model parameters, objectives, and descriptions are given, multiple-beam antenna frequency reuse capacity and interbeam isolation analysis of the two types of reflectors are discussed as well as future developments of the program model.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-163632 , JPL-PUB-80-52
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  • 94
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    Multiple band circularly polarized microstrip antenna (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A multiple antenna assembly for communicating electromagnetic radiation is disclosed. An antenna element stack is constructed of a plurality of elliptical lamina antenna elements mutally separated by layers of dielectric material, and separated from a ground plane by dielectric material. The antenna assembly is coupled through a feed line in contact with the top antenna element. A conductor joins the remaining antenna elements to the ground plane. Each individual antenna element is operable for communication reception and transmission within a frequency band determined by the size of the particular antenna element. The sizes of the antenna elements may be selected to provide electromagnetic radiation communication over several distinct frequency bands, or to connect the individual bands into a broad band.
    Keywords: COMMUNICATIONS AND RADAR
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  • 95
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    Computer prediction of large reflector antenna radiation properties (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A FORTRAN program for calculating reflector antenna radiation patterns was rewritten and extended to include reflectors composed of a number of panels. These individual panels must be analytic surfaces. The theoretical foundation for the program is as follows: Geometrical optics techniques are used to trace rays from a feed antenna to the reflector surface and back to a mathematical plane just in front of the reflector. The resulting tangential electric field distribution, assumed to be the only source of forward radiation, is integrated numerically to calculate the radiation pattern for a desired set of angles. When the reflector is composed of more than one panel, each panel is treated as a separated antenna, the ray-tracing procedure and integration being repeated for each panel. The results of the individual aperture plane integrations are stored and summed to yield the relative electric field strength over the angles of interest. An example and several test cases are included to demonstrate the use of the program and verify the new method of computation.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-163703
    Format: application/pdf
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    Shuttle orbiter Ku-band radar/communications system design evaluation. Ku band bent-pipe channel performance evaluation (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Because of difficulties with the bit detector of the SPA mode 1 channel 3 input port, a new bit synchronizer was required. The two prime candidate designs are described and analyzed. The selected design is a modification of one which utilizes a phase frequency detector to track the received data clock frequency and a mid-bit transition point sample detector to generate a bit timing error (phase error) signal to control the relative phase between the local clock and the local data stream. The model used to calculate the effects of cable attenuation and rise time degradation is discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-160696 , R8006-5
    Format: application/pdf
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  • 97
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    Wireless microphone communication system telephonics P/N 484D000-1 (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The wireless microphone is a lightweight, portable, wireless voice communications device for use by the crew of the space shuttle orbiter. The wireless microphone allows the crew to have normal hands-free voice communication while they are performing various mission activities. The unit is designed to transmit at 455 or 500 kilohertz and employs narrow band FM modulation. Two orthogonally placed antennas are used to insure good reception at the receiver.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-160731 , WMCS-001
    Format: application/pdf
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  • 98
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    Electro-optics laboratory evaluation: Deutsch optical waveguide connectors (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A description of a test program evaluating the performance of an optical waveguide connector system is presented. Both quality and effectiveness of connections made in an optical fiber, performance of the equipment used and applicability of equipment and components to field conditions are reviewed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-74108 , KSC-TR-32-1
    Format: application/pdf
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  • 99
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    Critique of the Hughes Aircraft shuttle Ku band leading edge bit synchronizer (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A bit synchronizer is analyzed via timing diagrams in a noise-free environment. It is believed that this new bit synchronizer will track the rising edge of the data bits with 25% asymmetry and up to a 90 deg phase shift between the received clock and data bit timing. In addition, the data bits will be demodulated correctly. It is not true that phase shifts larger than 90 deg will necessarily be corrected by this bit synchronizer. However, the specifications currently require the loop to operate over only a + or - 75 deg phase shift between the received data stream leading edges and the bit synchronizer leading edges; consequently, there should be no problem.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-160661 , R8005-2
    Format: application/pdf
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  • 100
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    Shuttle Ku-band and S-band communications implementation study (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Various aspects of the shuttle orbiter S-band network communication system, the S-band payload communication system, and the Ku-band communication system are considered. A method is proposed for obtaining more accurate S-band antenna patterns of the actual shuttle orbiter vehicle during flight because the preliminary antenna patterns using mock-ups are not realistic that they do not include the effects of additional appendages such as wings and tail structures. The Ku-band communication system is discussed especially the TDRS antenna pointing accuracy with respect to the orbiter and the modifications required and resulting performance characteristics of the convolutionally encoded high data rate return link to maintain bit synchronizer lock on the ground. The TDRS user constraints on data bit clock jitter and data asymmetry on unbalanced QPSK with noisy phase references are included. The S-band payload communication system study is outlined including the advantages and experimental results of a peak regulator design built and evaluated by Axiomatrix for the bent-pipe link versus the existing RMS-type regulator. The nominal sweep rate for the deep-space transponder of 250 Hz/s, and effects of phase noise on the performance of a communication system are analyzed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-160662 , R8005-3
    Format: application/pdf
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