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  • 1
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    A periodic moment method solution for TM scattering from lossy dielectric bodies with application to wedge absorber (1992)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The periodic moment method (PMM) solution for the scattering from two-dimensional lossy dielectric bodies is developed in this paper. The purpose is to design microwave wedge absorber for low reflectivity so that one can improve the performance of anechoic chamber measurements. With PMM, the reflection and transmission coefficients of periodically distributed bodies illuminated by a plane wave have been accurately calculated using a Cray Y-MP supercomputer. Through these studies, some wedge absorber configurations have been designed, fabricated, and then tested in the OSU/ESL compact range measurement facility. Two 8 in. commercial wedges, a curved wedge, and a four-layer wedge are studied in this paper. In all cases, good agreement between calculations and measurements has been obtained.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation (ISSN 0018-926X); 40; 6, Ju; 652-660
    Format: text
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  • 2
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    An ultra-wideband antenna for pulsed applications (1993)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: A wideband feed is proposed to support wideband radiation, and a design process is presented for a slotline bowtie hybrid (SBH) antenna based on specified pattern characteristics. Measured results are presented to demonstrate the pattern control of the antenna over its bandwidth. Impulse response plots are used to illustrate the pulse performance of this antenna type. For the antenna discussed here, the bandwidth was measured to be 6 to 1 and actually is expected to be larger.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Microwave Journal (ISSN 0192-6225); 36; 9; p. 136, 138, 141-143
    Format: text
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  • 3
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    Mobile satellite regulation in the United States (1990)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: During the last decade, the U.S. FCC has developed the regulatory structure for the provision of mobile services via satellite. In May 1989, the FCC awarded American Mobile Satellite Corporation (AMSC) a license to provide the full range of domestic mobile satellite services in the U.S. At that time, the FCC reaffirmed the U.S. mobile satellite industry structure and spectrum allocations that had been adopted previously. Also in May 1989, the FCC authorized the Communications Satellite Corporation (COMSAT), the U.S. Signatory to Inmarsat, to provide international aeronautical satellite service via the Inmarsat system. Earlier in 1989, the FCC permitted the use of Ku-band satellites to provide messaging and tracking services. In the mid-1980's, the FCC established the Radiodetermination Satellite Service and awarded licenses. Among the mobile satellite matters currently facing the FCC are whether additional spectrum should be allocated for domestic 'generic' mobile satellite services, the regulatory structure for the provision of mobile satellite service on an interim basis before AMSC launches its dedicated satellites, and whether to authorize a low earth orbit satellite system to provide mobile data service.
    Keywords: COMMUNICATIONS AND RADAR
    Type: JPL, California Inst. of Tech., Proceedings of the 2nd International Mobile Satellite Conference (IMSC 1990); p 463-467
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  • 4
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    Automatic translation among spoken languages (1994)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The Machine Aided Voice Translation (MAVT) system was developed in response to the shortage of experienced military field interrogators with both foreign language proficiency and interrogation skills. Combining speech recognition, machine translation, and speech generation technologies, the MAVT accepts an interrogator's spoken English question and translates it into spoken Spanish. The spoken Spanish response of the potential informant can then be translated into spoken English. Potential military and civilian applications for automatic spoken language translation technology are discussed in this paper.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA, Washingtion, Technology 2003: The Fourth National Technology Transfer Conference and Exposition, Volume 2; p 139-142
    Format: application/pdf
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  • 5
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    Defocussing characteristics of the ACTS, T1-VSAT Earth terminal antennas (1994)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: This report describes a study, the purpose of which was to determine the characteristics of two reflector antennas, as the reflector feed is moved away from the focus. The antennas are a 1.2 meter and a 2.44 meter reflector that will be used in the T1-VSAT earth terminals for the Advanced Communications Technology Satellite (ACTS). These terminals have been constructed in such a way that is inconvenient to use attenuators to control the gain of the signal that is directed toward the satellite. Feed defocusing was proposed as a simple, convenient way to achieve the required gain control. The study was performed in two parts. In order to determine the feasibility of the technique, a theoretical analysis was performed to obtain the gain, beamwidth and far-field pattern of the antennas, as a function of feed displacement. An experimental investigation followed in which patterns of the 1.2 meter antenna were obtained through measurement in the NASA Lewis Research Center, Near-Field Antenna Test Facility. Results of the theoretical and experimental investigation are presented for both uplink (30 GHz) and downlink (20 GHz) frequencies.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-106420 , E-8257 , NAS 1.15:106420
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  • 6
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    Simulation and analysis of airborne antenna radiation patterns (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The objective is to develop an accurate and efficient analytic solution for predicting high frequency radiation patterns of fuselage-mounted airborne antennas. This is an analytic study of airborne antenna patterns using the Uniform Geometrical Theory of Diffraction (UTD). The aircraft is modeled in its most basic form so that the solution is applicable to general-type aircraft. The fuselage is modeled as a perfectly conducting composite ellipsoid; whereas, the wings, stabilizers, nose, fuel tanks, and engines, are simulated as perfectly conducting flat plates that can be attached to the fuselage and/or to each other. The composite-ellipsoid fuselage model is necessary to successfully simulate the wide variety of real world fuselage shapes. Since the antenna is mounted on the fuselage, it has a dominant effect on the resulting radiation pattern so it must be simulated accurately, especially near the antenna. Various radiation patterns are calculated for commercial, private, and military aircraft, and the Space Shuttle Orbiter. The application of this solution to numerous practical airborne antenna problems illustrates its versatility and design capability. In most cases, the solution accuracy is verified by the comparisons between the calculated and measured data.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-181250 , NAS 1.26:181250 , REPT-716199-1
    Format: application/pdf
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  • 7
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    A GTD analysis of ogive pedestal (1987)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The metal ogive pedestal is claimed to have low radar cross section and low observability features. This study uses the Geometric Theory of Diffraction (GTD) to analyze the pedestal scattering for three cases: direct backscattered field, backscattered field structure, and target/pedestal multiple scattering. This study can be used to evaluate the various ways that the metal conical ogive pedestal can effect the performance of a high quality radar cross section measurement system.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-181269 , NAS 1.26:181269 , REPT-716148-8
    Format: application/pdf
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  • 8
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    Airborne antenna radiation pattern code user's manual (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The use of a newly developed computer code to analyze the radiation patterns of antennas mounted on a ellipsoid and in the presence of a set of finite flat plates is described. It is shown how the code allows the user to simulate a wide variety of complex electromagnetic radiation problems using the ellipsoid/plates model. The code has the capacity of calculating radiation patterns around an arbitrary conical cut specified by the user. The organization of the code, definition of input and output data, and numerous practical examples are also presented. The analysis is based on the Uniform Geometrical Theory of Diffraction (UTD), and most of the computed patterns are compared with experimental results to show the accuracy of this solution.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-181249 , NAS 1.26:181249 , REPT-716199-4
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  • 9
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    User manual for semi-circular compact range reflector code: Version 2 (1987)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A computer code has been developed at the Ohio State University ElectroScience Laboratory to analyze a semi-circular paraboloidal reflector with or without a rolled edge at the top and a skirt at the bottom. The code can be used to compute the total near field of the reflector or its individual components at a given distance from the center of the paraboloid. The code computes the fields along a radial, horizontal, vertical or axial cut at that distance. Thus, it is very effective in computing the size of the sweet spot for a semi-circular compact range reflector. This report describes the operation of the code. Various input and output statements are explained. Some results obtained using the computer code are presented to illustrate the code's capability as well as being samples of input/output sets.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-180550 , NAS 1.26:180550 , TR-716148-18
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  • 10
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    User's manual for semi-circular compact range reflector code (1986)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A computer code was developed to analyze a semi-circular paraboloidal reflector antenna with a rolled edge at the top and a skirt at the bottom. The code can be used to compute the total near field of the antenna or its individual components at a given distance from the center of the paraboloid. Thus, it is very effective in computing the size of the sweet spot for RCS or antenna measurement. The operation of the code is described. Various input and output statements are explained. Some results obtained using the computer code are presented to illustrate the code's capability as well as being samples of input/output sets.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-180690 , NAS 1.26:180690 , ESL-TR-716148-11
    Format: application/pdf
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