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  • 1
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    Preliminary antenna radiation pattern calculations for the ATS F flex rib reflector (1970)
    In:  CASI
    Details
    Publication Date: 2006-04-25
    Description: Computer program for calculating radiation pattern of ATS 6 flexible rib-reinforced reflector
    Keywords: COMMUNICATIONS
    Type: NIFICANT ACCOMPLISHMENTS IN SCI. AND TECHNOL. AT GODDARD SPACE FLIGHT CENTER 1970; P 259-262
    Format: text
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  • 2
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    Analysis of a dual-reflector antenna system using physical optics and digital computers (1972)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The application of physical-optics diffraction theory to a deployable dual-reflector geometry is discussed. The methods employed are not restricted to the Conical-Gregorian antenna, but apply in a general way to dual and even multiple reflector systems. Complex vector wave methods are used in the Fresnel and Fraunhofer regions of the reflectors. Field amplitude, phase, polarization data, and time average Poynting vectors are obtained via an IBM 360/91 digital computer. Focal region characteristics are plotted with the aid of a CalComp plotter. Comparison between the GSFC Huygens wavelet approach, JPL measurements, and JPL computer results based on the near field spherical wave expansion method are made wherever possible.
    Keywords: COMMUNICATIONS
    Type: NASA-TM-X-66223 , X-811-72-392
    Format: application/pdf
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  • 3
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    Diffraction studies applicable to 60-foot microwave research facilities (1973)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The principal features of this document are the analysis of a large dual-reflector antenna system by vector Kirchhoff theory, the evaluation of subreflector aperture-blocking, determination of the diffraction and blockage effects of a subreflector mounting structure, and an estimate of strut-blockage effects. Most of the computations are for a frequency of 15.3 GHz, and were carried out using the IBM 360/91 and 360/95 systems at Goddard Space Flight Center. The FORTRAN 4 computer program used to perform the computations is of a general and modular type so that various system parameters such as frequency, eccentricity, diameter, focal-length, etc. can be varied at will. The parameters of the 60-foot NRL Ku-band installation at Waldorf, Maryland, were entered into the program for purposes of this report. Similar calculations could be performed for the NELC installation at La Posta, California, the NASA Wallops Station facility in Virginia, and other antenna systems, by a simple change in IBM control cards. A comparison is made between secondary radiation patterns of the NRL antenna measured by DOD Satellite and those obtained by analytical/numerical methods at a frequency of 7.3 GHz.
    Keywords: FACILITIES, RESEARCH, AND SUPPORT
    Type: NASA-TM-X-70707 , X-811-73-39
    Format: application/pdf
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  • 4
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    The calculation of electromagnetic fields in the Fresnel and Fraunhofer regions using numerical integration methods (1971)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Some results obtained with a digital computer program written at Goddard Space Flight Center to obtain electromagnetic fields scattered by perfectly reflecting surfaces are presented. For purposes of illustration a paraboloidal reflector was illuminated at radio frequencies in the simulation for both receiving and transmitting modes of operation. Fields were computed in the Fresnel and Fraunhofer regions. A dual-reflector system (Cassegrain) was also simulated for the transmitting case, and fields were computed in the Fraunhofer region. Appended results include derivations which show that the vector Kirchhoff-Kottler formulation has an equivalent form requiring only incident magnetic fields as a driving function. Satisfaction of the radiation conditions at infinity by the equivalent form is demonstrated by a conversion from Cartesian to spherical vector operators. A subsequent development presents the formulation by which Fresnel or Fraunhofer patterns are obtainable for dual-reflector systems. A discussion of the time-average Poynting vector is also appended.
    Keywords: PHYSICS, GENERAL
    Type: NASA-TM-X-65779 , X-811-71-392
    Format: application/pdf
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  • 5
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    The calculation of electromagnetic fields by the Kirchhoff-Kottler method (1970)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Numerical evaluation of Kirchhoff-Kottler formulation of electromagnetic field backscatter and application to antenna surfaces
    Keywords: COMMUNICATIONS
    Type: NASA-TM-X-65340 , X-525-70-293
    Format: application/pdf
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  • 6
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    Electronic scanning of 2-channel monopulse patterns (1970)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Scanning method involves separation of scanning capability into two independent degrees of freedom. One degree of freedom corresponds to azimuthal scanning and other to elevation scanning on spiral coordinate axes. Scanning of both prime-feed and mirrored patterns is accomplished with reduction of mechanical vibration damage to large antennas.
    Keywords: ELECTRONIC SYSTEMS
    Type: GSC-10299
    Format: application/pdf
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  • 7
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    Variable-beamwidth monopulse antennas (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The merits of nine methods for zooming microwave amplitude-sensing monopulse antenna patterns are discussed. Of these, six are directly related to the TDRSS (Tracking Data Relay Satellite System) and are compatible with a deployable-mesh pseudo-paraboloidal main reflector. The remaining three methods utilize radically different geometrical configurations that depart considerably from the TDRSS parameters existing at this time. Preservation of the monopulse postulates is considered to be of prime importance for any variable-beamwidth candidate, however, it is allowed that approximate satisfaction of the postulates should be accepted for practical reasons. All of the methods discussed admit free choice of the polarization state, and the zooming function is never predicated on polarization. Exploration of the zooming techniques was carried out almost entirely by means of the Kirchhoff-Kottler vector diffraction program. The program generates electric and magnetic field intensity, associated phase, and time-average Poynting vector power flow in the intermediate near-field and far-field zones in both receive and transmit modes of operation. A few of the concepts have been verified experimentally with excellent agreement between theory and practice.
    Keywords: COMMUNICATIONS
    Type: NASA-TM-X-70650 , X-811-74-62
    Format: application/pdf
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  • 8
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    Antennas for spaceborne microwave radiometers (1974)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Principles and applications of microwave radiometry to remote sensing of the earth from satellites are reviewed. Examples of some spaceborne radiometer systems currently in use or under consideration are given. The requirements on performance characteristics of microwave antennas for such spaceborne earth sensing radiometers, such as coverage, scanning, spatial resolution, insertion loss, beam efficiency, polarization purity, etc., and their effects on the overall radiometer system performance are discussed.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: EASCON ''74; Electronics and Aerospace Systems Convention; Oct 07, 1974 - Oct 09, 1974; Washington, DC
    Format: text
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  • 9
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    Electronic scanning of 2-channel monopulse patterns Patent (1970)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Monopulse scanning network for scanning volumetric antenna pattern
    Keywords: ELECTRONIC EQUIPMENT
    Format: application/pdf
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  • 10
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    Variable beamwidth monopulse feed for Tracking and Data Relay Satellite (TDRS) (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The Tracking and Data Relay Satellite with a set of circularly-polarized, amplitude-sensing monopulse patterns suitable for acquiring and tracking user spacecraft at Ku-band (15.0 GHz) is discussed. The possibility of increasing the less than 0.4-degree half-power beamwidth of the data beam to almost 1.0 degree during the acquisition phase is predicated on the use of feeds situated in the first bright-ring of the Airy diffraction structure. A complex-vector simulation equivalent to the Kirchhoff-Kottler or Franz formulations is used to compute transmitted and received field information for a dual-reflector (Cassegrain) antenna configuration in a three-dimensional space.
    Keywords: COMMUNICATIONS
    Type: NASA-TM-X-70737 , X-811-74-170
    Format: application/pdf
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