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  • Inorganic Chemistry  (63)
  • Organic Chemistry  (50)
  • COMMUNICATIONS AND RADAR  (14)
  • Industrial Chemistry
  • 1990-1994  (127)
  • 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
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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
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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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    A novel antenna for ultra-wide-band applications (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: An ultrawideband antenna based on a slotline feed structure, a bowtie horn, and a rolled edge termination was developed, analyzed, and measured. Empirical data showed that its beamwidths and bandwidth are dependent on its physical dimensions which are easily controllable by an antenna designer. Measured patterns of models with various radiation properties are shown to substantiate these design rules. A flat plateau-like main beam, low voltage standing-wave ratio (VSWR), the ability to produce both wide (60 deg) and narrow (30 deg) half-power beamwidths, low sidelobes and backlobe (40-50 dB down), low cross-polarized levels (20-25 dB down), and independent control of E- and H-plane beamwidths over an ultrawide bandwidth, say 2-18 GHz, are some of the strong points of this antenna type.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation (ISSN 0018-926X); 40; 7 Ju; 755-760
    Format: text
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  • 7
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    Stray signal requirements for compact range reflectors based on RCS measurement errors (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: The authors present a performance criterion for compact range reflectors such that their edge diffracted stray signal levels meet a reasonable radar cross section (RCS) measurement error requirement. It is shown by example that one of the significant error sources is the diffracted fields emanating from the edges or junctions of the reflector. This measurement error is demonstrated by placing a diagonal square flat plate in the target zone and rotating it to appropriate angles. These angles are determined by bisecting the plane wave and stray signal directions. This results in a peak bistatic measurement of the edge diffracted stray signal. It is proposed that the diagonal flat plate be used to evaluate new reflector designs as well as existing systems. A reasonable stray signal performance level has been developed so that new reflector systems can be characterized in terms of an RCS measurement error requirement.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation (ISSN 0018-926X); 39; 1193-120
    Format: text
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  • 8
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    Scattering from thin dielectric straps surrounding a perfectly conducting structure (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Dielectric straps can support very heavy targets and have low backscattering levels, especially at low frequencies (below 8 GHz); thus, they can be used effectively to support targets during backscattered field measurements. In this paper, the scattered fields of nonmagnetic dielectric straps surrounding a perfectly conducting structure are presented, and the computed results are compared with experimental data. Empirical formulas for the strap scattered fields are also given. These formulas are good for general convex structures whose radii of curvature are large compared with the wavelength and are expected to give a reasonable estimate of the true backscattered fields from the dielectric straps when used as a target support structure.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation (ISSN 0018-926X); 41; 4; p. 442-447.
    Format: text
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  • 9
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    Slope effects on shortwave radiation components and net radiation (1992)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The main objective of the International Satellite Land Surface Climatology Project (ISLSCP) has been stated as 'the development of techniques that may be applied to satellite observations of the radiation reflected and emitted from the Earth to yield quantitative information concerning land surface climatological conditions.' The major field study, FIFE (the First ISLSCP Field Experiment), was conducted in 1978-89 to accomplish this objective. Four intensive field campaigns (IFC's) were carried out in 1987 and one in 1989. Factors contributing to observed reflected radiation from the FIFE site must be understood before the radiation observed by satellites can be used to quantify surface processes. Analysis since our last report has focused on slope effects on incoming and outgoing shortwave radiation and net radiation from data collected in 1989.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-192199 , NAS 1.26:192199
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  • 10
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    Data communication network at the ASRM facility (1993)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The main objective of the report is to present the overall communication network structure for the Advanced Solid Rocket Motor (ASRM) facility being built at Yellow Creek near Iuka, Mississippi. This report is compiled using information received from NASA/MSFC, LMSC, AAD, and RUST Inc. As per the information gathered, the overall network structure will have one logical FDDI ring acting as a backbone for the whole complex. The buildings will be grouped into two categories viz. manufacturing critical and manufacturing non-critical. The manufacturing critical buildings will be connected via FDDI to the Operational Information System (OIS) in the main computing center in B 1000. The manufacturing non-critical buildings will be connected by 10BASE-FL to the Business Information System (BIS) in the main computing center. The workcells will be connected to the Area Supervisory Computers (ASCs) through the nearest manufacturing critical hub and one of the OIS hubs. The network structure described in this report will be the basis for simulations to be carried out next year. The Comdisco's Block Oriented Network Simulator (BONeS) will be used for the network simulation. The main aim of the simulations will be to evaluate the loading of the OIS, the BIS, the ASCs, and the network links by the traffic generated by the workstations and workcells throughout the site.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-192085 , NAS 1.26:192085
    Format: application/pdf
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