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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,081 records · Page 60
All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

Multipath/RFI/modulation study for DRSS-RFI problem: Voice coding and intelligibility testing for a satellite-based air traffic control system

Analog and digital voice coding techniques for application to an L-band satellite-basedair traffic control (ATC) system for over ocean deployment are examined. In addition to performance, the techniques are compared on the basis of cost, size, weight, power consumption, availability, reliability, and multiplexing features. Candidate systems are chosen on the bases of minimum required RF bandwidth and received carrier-to-noise density ratios. A detailed survey of automated and nonautomated intelligibility testing methods and devices is presented and comparisons given. Subjective evaluation of speech system by preference tests is considered. Conclusion and recommendations are developed regarding the selection of the voice system. Likewise, conclusions and recommendations are developed for the appropriate use of intelligibility tests, speech quality measurements, and preference tests with the framework of the proposed ATC system.

Birch, J. N.↗
NASA NTRS1972

Matched pair conical spiral antennas

A matched pair of VHF (220-260 MHz) conical spiral antennas for use in a rocket-tracking interferometer array was designed and tested. While gain, bandwidth, impedance, and pattern measurements met specifications, the phase match between antennas at low elevations was not equal to the design goal.

Metzler, R. E.↗
NASA NTRS1971

Disaster warning satellite study

The Disaster Warning Satellite System is described. It will provide NOAA with an independent, mass communication system for the purpose of warning the public of impending disaster and issuing bulletins for corrective action to protect lives and property. The system consists of three major segments. The first segment is the network of state or regional offices that communicate with the central ground station; the second segment is the satellite that relays information from ground stations to home receivers; the third segment is composed of the home receivers that receive information from the satellite and provide an audio output to the public. The ground stations required in this system are linked together by two, separate, voice bandwidth communication channels on the Disaster Warning Satellites so that a communications link would be available in the event of disruption of land line service.

Source record↗
NASA NTRS1972

Radar signature and systems studies at Kansas University

The radar signature and systems studies described have concentrated in two areas: octave bandwidths radar spectrometry using a truck-mounted system, and scatterometry using primarily the 13.3 GHz system on aircraft. In addition, the results of the experiments to date have been synthesized into a pair of representative designs for spacecraft radar systems: one for small spacecraft and one for large spacecraft.

Moore, R. K.↗
NASA NTRS1972

Investigate optimum way of adding wideband capability and recommend a design for modification of one government furnished AM baseband demultiplexer, phase 1

The effort to analyze and test the Teledyne/Adcom model G-146 demultiplexer to determine the feasibility and optimum method(s) for modifying the unit for broadband operation is described. The desired bandwidths under consideration included 2, 4, and 8 kHz for double sideband and quadrature double sideband, and 4, 8, and 16 kHz for single sideband.

Source record↗
NASA NTRS1972

Relabeling of finite element meshes using a random process

An algorithm is presented to relabel automatically the nodes of an arbitrary finite-element mesh. The purpose of such relabeling is to reduce the bandwidth of the master stiffness matrix produced by the finite-element method. The algorithm uses a random process for the relabeling. Computing time is reduced substantially, compared to systematic methods.

Roberts, E., Jr.↗
NASA NTRS1971

Vertical sounding of the atmosphere with the Nimbus IV infrared spectrometer experiment.

Nimbus III and IV meteorological satellite data obtained on a Michelson interferometer are used as a basis for sounding the vertical temperature and water-vapor and ozone content profiles in the atmosphere. Selection of suitable locations and bandwidths for making such soundings efficient is discussed. Several transmittance models of the atmosphere, and terrain properties and cloud emissivity effects as factors influencing the sounding results are considered.

Conrath, B. J.↗
NASA NTRS1971

Broad-band dipole design using the method of moments.

Application of the method of moments to the problem of broad-band dipole design. For electrically small antennas, top-loaded geometries appear to maximize bandwidth. For dimensions of the order of a wavelength, a class of dipole shapes is given which yields a VSWR of less than 1.1 with respect to a 100-ohm transmission line over a frequency range of 1.8 to 1. The beam shape is essentially that of a dipole over the band.

Kalafus, R. M.↗
NASA NTRS1971

A unified approach to the classification of visual data systems.

Description of an approach to attaining a unified means of characterizing film, TV, and optical data systems. The concept is based on the premise that all of these imaging systems can be described by an equation similar to the ideal imaging system described by Rose (1948). This technique permits the direct comparison of film and TV performance without converting speed, film resolution lines, TV resolution lines, highlight output current and video bandwidth into compatible units, only to find some essential element of the conversion has been omitted from the particular specification in use. Most important, it permits system performance criteria to be based on input and output criteria without extensive manipulation of the elements between input and output.

Black, J.↗
NASA NTRS1972

Optimum filters for narrow-band frequency modulation.

The results of a computer search for the optimum type of bandpass filter for low-index angle-modulated signals are reported. The bandpass filters are discussed in terms of their low-pass prototypes. Only filter functions with constant numerators are considered. The pole locations for the optimum filters of several cases are shown in a table. The results are fairly independent of modulation index and bandwidth.

Shelton, R. D.↗
NASA NTRS1972

High-sensitivity receiver for infrared laser communications.

Description of a high-sensitivity wide-bandwidth 10.6-micron heterodyne receiver for space and ground operational use. The receiver includes a cooled HgCdTe infrared mixer diode, a conical scanner for spatial tracking, an acquisition channel for spatial search and station alignment, and an automatic frequency-control channel to maintain a fixed laser frequency offset. The infrared mixer is designed to provide nearly quantum-noise-limited operation over an extended range of mixer temperature, bias voltage, and intermediate frequency. The resultant experimental receiver has a measured noise equivalent power of less than 10 to the minus 19th W/Hz over the 15- to 40-MHz i.f. band for mixer temperatures from 85 to 115 K, and less than 2 x 10 to the minus 19th W/Hz up to 140 K. Mixer 3-dB cutoff frequencies as high as 420 MHz were measured at a mixer temperature of 125 K. An analysis and engineering equations are given for receiver noise components, noise equivalent power, available mixer conversion gain, mixer transducer gain, and quantum-noise factor in terms of such factors as mixer parameters, quantum efficiency, mixer temperature, dynamic conductance, bias voltage, local oscillator power, and i.f. amplifier characteristics.

Peyton, B. J.↗
NASA NTRS1971

An interlaboratory comparison of piston-cylinder pressure calibration using the albite-breakdown reaction.

An attempt is made to compare pressure calibration methods among several laboratories in an unbiased way to produce some indication of the bandwidth of observations on the pressure of an equilibrium reaction where sources of discrepancy not resulting from pressure calibration are likely to have been eliminated. The reaction chosen is the breakdown of albite to jadeite and quartz under pressure.

Johannes, W.↗
NASA NTRS1972

Simulation of superposed coherent and chaotic radiation of arbitrary spectral shape.

A simulation technique is described and utilized to generate superposed coherent and chaotic (thermal) radiation of arbitrary spectral shape. The statistical properties of a simulated radiation field with a Lorentzian spectral density are investigated with a photoelectron counting experiment. The experimental photocount distribution and normalized mth-order factorial moments are compared to theory and verify that the simulated radiation field, an appropriately modulated laser beam, has the expected statistical properties. The concept described indicates that one may, in principle, generate a thermal source of comparable intensity to that of a laser, arbitrary spectral shape, and bandwidth.

Ruggieri, N. F.↗
NASA NTRS1972

A millimeter-wave pumped X-band uncooled parametric amplifier.

GaAs Schottky barrier varactors with a cutoff frequency of 800 GHz are used in a balanced diode-type parametric amplifier operating with a signal frequency at 7.5 GHz. The room-temperature parameters of the amplifier are a gain of 15 dB, a bandwidth of 500 MHz, and an excess noise temperature of 63 K (a noise figure of 0.86 dB).

Dickens, L. E.↗
NASA NTRS1972

A surface wave spread spectrum communication link.

This development has resulted in a fast lock-up, 8-MHz bandwidth, 8-KHz data rate, spread spectrum communication link breadboard that is implemented using surface wave devices as the primary signal generators and signal processing elements. It uses surface wave tapped delay lines (SWTDL's) in the transmitter to generate the signals and in the receiver to match filter detect them. The system also incorporates a re-entry delay line (circulating integrator) which increases the effective code length per data bit by eight-fold.

Fugit, B. R.↗
NASA NTRS1972

Simplified method for measuring mean opacities and effective absorption coefficients.

Use of wide bandwidths and a number of path lengths to obtain mean opacities and effective absorption coefficients. This method is applicable if the temperatures and pressures at which these qualities are desired can be duplicated experimentally. Additional restrictions are that the gas in the experiments must be essentially isothermal, homogeneous, nonscattering, and in local thermodynamic equilibrium. The method is most advantageous in shock tube experiments and experiments utilizing a pulsed arc of cylindrical symmetry viewed axially.

Patch, R. W.↗