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  • Other Sources  (8)
  • Electronics and Electrical Engineering  (5)
  • Instrumentation and Photography  (2)
  • Astrodynamics  (1)
  • 1
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    An Alternate Set of Basis Functions for the Electromagnetic Solution of Arbitrarily-Shaped, Three-Dimensional, Closed, Conducting Bodies Using Method of Moments (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: In this work, we present an alternate set of basis functions, each defined over a pair of planar triangular patches, for the method of moments solution of electromagnetic scattering and radiation problems associated with arbitrarily-shaped, closed, conducting surfaces. The present basis functions are point-wise orthogonal to the pulse basis functions previously defined. The prime motivation to develop the present set of basis functions is to utilize them for the electromagnetic solution of dielectric bodies using a surface integral equation formulation which involves both electric and magnetic cur- rents. However, in the present work, only the conducting body solution is presented and compared with other data.
    Keywords: Electronics and Electrical Engineering
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  • 2
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    New Basis Functions for the Electromagnetic Solution of Arbitrarily-shaped, Three Dimensional Conducting Bodies using Method of Moments (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: In this work, we present a new set of basis functions, defined over a pair of planar triangular patches, for the solution of electromagnetic scattering and radiation problems associated with arbitrarily-shaped surfaces using the method of moments solution procedure. The basis functions are constant over the function subdomain and resemble pulse functions for one and two dimensional problems. Further, another set of basis functions, point-wise orthogonal to the first set, is also defined over the same function space. The primary objective of developing these basis functions is to utilize them for the electromagnetic solution involving conducting, dielectric, and composite bodies. However, in the present work, only the conducting body solution is presented and compared with other data.
    Keywords: Electronics and Electrical Engineering
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  • 3
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    Comparison of Thermal Coefficients for Two Microwave Detectors (2001)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: Laboratory measurements were performed to compare the thermal coefficients of two microwave detectors that might be used for direct detection in L-band radiometers. In particular it was desired to compare the performance of a new-technology flash ADC (analog-to-digital converter) against that of an older-technology diode detector in series with a VFC (voltage-to-frequency converter). The outputs of two state-of-the-art detectors were recorded as a constant 1.414-GHz signal was input and the physical temperatures of the detectors were varied over a range of 10 C. As a further experiment, each detector was tested with a noise diode source and with a sine wave synthesizer source. Thermal coefficients were computed in terms of W/C and in terms of ppt/C at nominal operating temperatures reasonable for the individual devices. Finally, thermal coefficients were calculated in K/C to indicate the change in brightness temperature seen by a theoretical sea surface salinity radiometer employing each detector. The K/C for the flash ADC was determined to be about 2.8 times that of the diode/VFC. Different reactions of the ADC to a noise input and a sine wave input indicated that ADC tests for radiometric purposes, such as this one, should be performed using a noise input.
    Keywords: Instrumentation and Photography
    Type: NASA/TM-2001-211258 , NAS 1.15:211258 , L-18091
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  • 4
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    Paired Pulse Basis Functions for the Method of Moments EFIE Solution of Electromagnetic Problems Involving Arbitrarily-shaped, Three-dimensional Dielectric Scatterers (2007)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A pair of basis functions is presented for the surface integral, method of moment solution of scattering by arbitrarily-shaped, three-dimensional dielectric bodies. Equivalent surface currents are represented by orthogonal unit pulse vectors in conjunction with triangular patch modeling. The electric field integral equation is employed with closed geometries for dielectric bodies; the method may also be applied to conductors. Radar cross section results are shown for dielectric bodies having canonical spherical, cylindrical, and cubic shapes. Pulse basis function results are compared to results by other methods.
    Keywords: Electronics and Electrical Engineering
    Type: Paper No. 1176736464 , 2007 Electromagnetic Code Consortium (EMCC) Annual Meeting; May 08, 2007 - May 10, 2007; San Diego, CA; United States
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  • 5
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    Atmospheric drag model for Cassini orbit determination during low altitude Titan flybys (2006)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: On April 16, 2005, the Cassini spacecraft performed its lowest altitude flyby of Titan to date, the Titan-5 flyby, flying 1027 km above the surface of Titan. This document discusses the development of a Titan atmospheric drag model for the purpose of the orbit determination of Cassini. Results will be presented for the Titan A flyby, the Titan-5 flyby as well as the most recent low altitude Titan flyby, Titan-7. Different solutions will be compared against OD performance in terms of the flyby B-plane parameters, spacecraft thrusting activity and drag estimates. These low altitude Titan flybys were an excellent opportunity to observe the effect of Titan's atmospheric drag on the orbit determination solution and results show that the drag was successfully modeled to provide accurate flyby solutions.
    Keywords: Astrodynamics
    Type: 16th AAS/AIAA Space Flight Mechanics Conference, Tampa, Florida; Jan 22, 2006 - Jan 26, 2006
    Format: text
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  • 6
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    New Basis Functions for the Electromagnetic Solution of Arbitrarily-shaped, Three Dimensional Conducting Bodies Using Method of Moments (2007)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: In this work, we present a new set of basis functions, de ned over a pair of planar triangular patches, for the solution of electromagnetic scattering and radiation problems associated with arbitrarily-shaped surfaces using the method of moments solution procedure. The basis functions are constant over the function subdomain and resemble pulse functions for one and two dimensional problems. Further, another set of basis functions, point-wise orthogonal to the first set, is also de ned over the same function space. The primary objective of developing these basis functions is to utilize them for the electromagnetic solution involving conducting, dielectric, and composite bodies. However, in the present work, only the conducting body solution is presented and compared with other data.
    Keywords: Electronics and Electrical Engineering
    Type: 23rd International Review of Progress in Applied Computational Electromagnetics (ACES 2007); Mar 19, 2007 - Mar 23, 2007; Verona; Italy
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  • 7
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    Electromagnetic Modeling for the Conformal Lightweight Antenna System for Aeronautical Communications Technologies (CLAS-ACT) Program: Final Report (2019)
    In:  CASI
    Details
    Publication Date: 2019-08-27
    Description: A series of electromagnetic simulations was conducted for the Conformal Lightweight Antenna System for Aeronautical Communications Technologies (CLAS-ACT) Program. The program designed, built, and flight tested a 14.25 GHz conformal patch array antenna for satellite communications on a T-34C airplane. Various studies were performed to evaluate the effects of antenna element spacing, array shape, signal taper, phased array pointing angle, null steering coefficients, antenna platform, and location on the airplane. This report documents the methods and some of the results of tests done over a 2 year period.
    Keywords: Electronics and Electrical Engineering
    Type: NASA/TM–2019-220293 , L-21041 , NF1676L-33695
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  • 8
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    Three Averaging Techniques for Reduction of Antenna Temperature Variance Measured by a Dicke Mode, C-Band Radiometer (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: As new radiometer technologies provide the possibility of greatly improved spatial resolution, their performance must also be evaluated in terms of expected sensitivity and absolute accuracy. As aperture size increases, the sensitivity of a Dicke mode radiometer can be maintained or improved by application of any or all of three digital averaging techniques: antenna data averaging with a greater than 50% antenna duty cycle, reference data averaging, and gain averaging. An experimental, noise-injection, benchtop radiometer at C-band showed a 68.5% reduction in Delta-T after all three averaging methods had been applied simultaneously. For any one antenna integration time, the optimum 34.8% reduction in Delta-T was realized by using an 83.3% antenna/reference duty cycle.
    Keywords: Instrumentation and Photography
    Type: NASA/TM-2000-210283 , L-17987 , NAS 1.15:210283
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