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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 901 records · Page 50
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Multiple-Symbol, Partially Coherent Detection of MPSK

Proposed method of reception of multiple-phase-shift-keyed (MPSK) radio signals involves multiple-symbol, partially coherent detection. Instead of attempting to determine phase of transmitted signal during each symbol period as in coherent detection, receiver acquires signal data during multiple-symbol observation interval, then produces maximum-likelihood-sequence estimate of phases transmitted during interval. Combination of coherent-reception and incoherent-reception decision rules are used.

Simon, Marvin K.↗
NASA NTRS1967

Detection and estimation theory

Dynamic systems, and electronic theory on nonlinear intervals, and performance bounds of optimum detection for Gaussian signals

ELECTRONICS↗
NASA NTRS1968

MLD's and the phase angle, alpha.

Alpha phase angle effect /angle between narrow band masker and tonal signal/ on binaural detection, discussing experiments failure

Jeffress, L. A.↗
NASA NTRS1972

Long range laser traversing system

A study was carried out to determine the feasibility of a man-portable receiver system for land survey, which would be capable of detecting the optical scatter due to molecular and aerosol constituents of the atmosphere from a vertical laser beam. Tests were run with a beacon and receiver separated by approximately one mile. The system was consistently able to detect the laser signal regardless of background conditions.

Caudill, L. O.↗
NASA NTRS1972

Transportable lunar-ranging system.

Description of a transportable transmitting unit for measuring distances to retroreflectors on the moon. The unit can be installed at any astronomical observatory where a large telescope is available to detect the received signal. The transmitter consists of a high radiance, frequency-doubled neodymium-glass laser and a coude optical system of moderate size. The measurements may eventually be used to study variations in the length of the earth's day, changes in the geographic location of the pole, and the drifting of the continents.

Lehr, C. G.↗
NASA NTRS1973

Cardiac R-wave detector with automatic sensitivity control

An electronic circuit that automatically changes its sensitivity was developed for detecting the bioelectric signal resulting from activation of the heart's ventricles. Regulation of sensitivity was accomplished with two feedback channels that maintain the sensitivity level between an upper and a lower limit. These limits are proportional to the R-wave amplitude. Tests on an experimental circuit demonstrated a capability to reject unwanted signal noise, illustrated difficulties encountered without sensitivity control, and presented closed loop transients which occurred for step changes in R-wave amplitude.

Gebben, V. D.↗
NASA NTRS1972

A study of multiplex data bus techniques for the space shuttle

A comprehensive technology base for the design of a multiplexed data bus subsystem is provided. Extensive analyses, both analytical and empirical, were performed. Subjects covered are classified under the following headings: requirements identification and analysis; transmission media studies; signal design and detection studies; synchronization, timing, and control studies; user-subsystem interface studies; operational reliability analyses; design of candidate data bus configurations; and evaluation of candidate data bus designs.

Kearney, R. J.↗
NASA NTRS1973

Gated high speed optical detector

The design, fabrication, and test of two gated, high speed optical detectors for use in high speed digital laser communication links are discussed. The optical detectors used a dynamic crossed field photomultiplier and electronics including dc bias and RF drive circuits, automatic remote synchronization circuits, automatic gain control circuits, and threshold detection circuits. The equipment is used to detect binary encoded signals from a mode locked neodynium laser.

Green, S. I.↗
NASA NTRS1974

Apparatus for scanning the surface of a cylindrical body

A laser scanning system for providing a two-dimensional display of a cylindrical surface, such as to display striae of a fired bullet is described. The cylinder is scanned along its axis by vibrating one mirror in the laser beam path, and is scanned in a direction normal to its axis by vibrating a second mirror in a direction normal to the first or by rotating the bullet. Scan control signals are adjusted in phase to produce a synchronized display of a video signal obtained from detection of scattered light from the surface thus scanned by a laser beam.

Nakich, R. B.↗
NASA NTRS1973

Two-component, self-aligning laser vector velocimeter

A newly developed laser Doppler velocimeter is described. The basic optical component of the instrument is a two-dimensional ultrasonic Bragg cell. It is shown that use of this Bragg cell simplifies the optics usually required for the more conventional velocimeters, allows measurement of two-vector components of velocity, requires no adjustment of alignment mirrors, and enables both velocity component signals to be detected with a single detector. Some results from experiments using this velocimeter in an atmospheric application are described.

Farmer, W. M.↗
NASA NTRS1975

Change in the high-energy radiation from the Crab

On 1973 July 23, the Cornell gamma-ray telescope had a second exposure to the Crab Nebula and pulsar via balloon flight from Palestine, Texas. On the previous flight, 1971 October 6, the signal from the pulsar had been unmistakably clear, especially at the highest energies (above 800 MeV), and an unpulsed component of similar average power had also been discernible. On the second flight, despite higher altitude, longer exposure, and improved electronics, the pulsed signal was barely detectable and the dc component not observable at all. The drop in intensity seems to increase with energy, being only a factor of 2 at 200 MeV but an order of magnitude at 1 GeV. There is some indication (not compelling) that the gamma-ray flux may have changed even within the 6-hour exposure. The first flight may have viewed the Crab in a state of enhanced high-energy emission correlated with the glitches that occurred on 1971 August 1 and October 25.

Greisen, K.↗
NASA NTRS1975

Infrared upconversion as a means of seeing in the dark

A new approach to seeing in the dark is described which is based on the principles of nonlinear optics employing a crystal such as lithium iodate. A nonlinear optical device capable of producing photons at higher frequencies from lower-frequency incident light is shown to upconvert infrared light directly into visible light. The major advantages of the infrared upconversion process is that it permits the infrared signal to be detected by photon-counting devices presently available for the visible spectral region, and that it can provide sensitivity to infrared radiation without the need for cryogenic cooling of the detector used. Early works on infrared upconversion are reviewed. The development of applications is discussed as to astronomical spectroscopy and infrared image upconversion involving either angular or positional resolution elements. The demonstration of infrared upconversion in rectangular waveguides of single-crystal GaAs by Anderson et al. (1971) indicates future possibilities in upconversion by the use of integrated optics devices.

Gurski, T. R.↗