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  • 1
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    Optimum coherent imaging of a limited field of view in the presence of angular and aperture noise (1977)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: The question of image distribution reconstruction for coherent illumination of an object located in the aperture far zone is considered from first principles without postulating any particular optical spread function. The object function is mathematically modeled as a complex random function of angular coordinates, and it is assumed that the object distribution of interest is angularly limited to a certain a priori assigned field of view (FOV). A linear reconstruction procedure that is uniformly optimal in the FOV is established by using the methods of statistical estimation. Two special cases are examined: imaging a limited sector of a wide-angle random scene and objects in the FOV immersed in a wide-angle background of angular noise. It is noted that the domain of application of the reconstruction method is restricted to microwave frequencies.
    Keywords: OPTICS
    Type: Franklin Institute; vol. 303
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    An antenna for limited scan in one plane - Design criteria and numerical simulation (1977)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: Aperture illumination is synthesized through the use of overlapping subarrays with independently controlled excitations. Detailed analysis and design criteria are provided for a specific limited-scan antenna configuration scanning in one plane. The number of phase shifts is the theoretical minimum corresponding to specified aperture size and field of view. Beam pointing and width are approximately constant for moderate frequency variation, and ultralow sidelobes outside the field of view can be produced at the cost of a slight loss of illumination efficiency. Accurate aperture illumination control makes for excellent independently specified sum and difference patterns in beamforming.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation; AP-25; Mar. 197
    Format: text
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  • 3
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    Maximum theoretical angular accuracy of planar and linear arrays of sensors (1977)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: The maximum theoretical accuracy in the angular location of a radiating object that can be obtained by using a planar or linear array is studied. The elements are assumed to have identical radiation patterns and the complex voltages observed at their ports are assumed to be subject to phase measurement errors, having normal probability density. An optimum scheme for the statistical extraction of the parameters defining the direction is established noting that the presence of thermal noise does not affect the structure of the estimator. Comparisons with the conventional multiple interferometric techniques are made.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: IEEE Transactions on Aerospace and Electronic Systems; AES-13; Mar. 197
    Format: text
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  • 4
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    Probe corrected far-field reconstruction from measurements on a cylinder: A novel formulation and efficient algorithm (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: A novel and numerically efficient method of far field evaluation from measurements taken on a cylinder is based on the representation of both the antenna and the probe fields as superpositions of plane waves. A system of two integral equations are established whose unknown functions are the azimuthal and elevation components of the antenna pattern and whose known terms are the set of measurement data taken with two different probes - the second probe in most practical instances being simply the same probe with a different geometrical orientation. The equations express the known data - for each angular position of the antenna under measurement - as the integrals of the products of the corresponding components of the unknown antenna and known probe patterns multiplied by a phase term. The convolutional nature of the integral equations makes their solutions straight-forward. If, as is virtually always the case, the probe is small or of moderate size so that the axis of rotation of the antenna mount is in the far field of the probe, the intervention of asymptotic techniques makes the solution numerically very efficient. The agreement of calculated and experimental patterns is excellent.
    Keywords: COMMUNICATIONS AND RADAR
    Type: ESA Antenna Testing Tech.; p 143-149
    Format: text
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  • 5
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    Surveyor landing radar test program review Final report (1967)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Test program evaluation and modifications for Surveyor radar altimeter and Doppler velocity sensor system
    Keywords: COMMUNICATIONS
    Type: NASA-CR-88883 , RTI-TRR-33
    Format: application/pdf
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  • 6
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    Integral equation formulation for probe corrected far-field reconstruction from measurements on a cylinder (1978)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: A method has been developed for far-field evaluation from measurements taken on a cylinder. The antenna and probe fields are represented by superpositions of plane waves, and two integral equations are derived whose functions are the elevation and azimuthal components of the antenna pattern. The known components are the measurements taken by either two probes or a single probe with two geometrical orientations. The convolutional nature of the integral equations makes Fourier analysis techniques applicable to a straightforward solution and an efficient computational procedure. Good agreement has been found between experimental and reconstructed patterns for both nominal and cross polarized field components.
    Keywords: SPACE COMMUNICATIONS, SPACECRAFT COMMUNICATIONS, COMMAND AND TRACKING
    Type: IEEE Transactions on Antennas and Propagation; AP-26; July 197
    Format: text
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