SEARCH · Engineering Papers
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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Phase-coherent communication systems with phase locked loops for data detector synchronization, calculating noisy timing effects on detection efficiency
Argon ion laser plasma tube anodic coherent oscillations and noise suppression, using secondary discharge between anode and auxiliary cathode
Coherent light photoelectric detection probability in background light passing through narrow band filter of rectangular or Lorentz frequency characteristics
Coherent optical data processing principles, discussing lens, diffraction, focused wave front, intensity vs amplitude and spectrum analyzer
Coherent optical data processing techniques, discussing diffraction phenomena, spectral analysis and holography
Coherent radiative phenomena with nontrivial zero-pi pulses propagation behavior in attenuating media
Approximate photocount statistics for superposition of coherent and chaotic radiation of Gaussian, triangular, square and Lorentzian shaped spectra
Signal mean and noise variance as direct functions of phase angle between signal component passed by bandpass limiter and coherent reference
Magnetic field detection by magnetometer with coherent magnetization rotation in thin magnetic film
Refraction and absorption length of coherent laser radiation propagating in high temperature cylindrical plasma column
Coherent electromagnetic excitation of optical transition levels by fluorescence measurement, obtaining dipole moment and relaxation times
Coherent periodic compressional micropulsations of geomagnetic field intensity and energetic electron fluxes at synchronous altitude during quiet day
Coherence theory of strong shock induced explosive gas ignition limit
An attempt to improve the performance of coherent carrier systems is described, involving optimizing the design point based upon a given practical optimizing criterion. The single-channel system is treated in detail, and a brief discussion is given on how to extend the technique to a two-channel system.
During a magnetically quiet interval the magnetic-field intensity and energetic electron fluxes at ATS 1 exhibited coherent modulations having a frequency of 33.8 cph and a duration of approximately 40 oscillations. The electron fluxes and the magnetic field oscillated in phase. The field perturbation reached 8 jamma (peak to peak) in the direction of the unperturbed geomagnetic field. The transverse component of the field perturbation was practically zero. The characteristics of the observed oscillations appear compatible with those of a compressional excitation of the outer magnetosphere. The substantially radial normal mode is perhaps driven by a bounce-resonant interaction with the 15-keV protons that populate the quiet-day ring current.
Coherent optical correlators are described in which complex spatial filters are recorded by a quasi-Fourier transform method. The high-pass spatial filtering effects (due to the dynamic range of photographic films) normally encountered in Vander Lugt type complex filters are not present in this system. Experimental results for both transmittive as well as reflective objects are presented. Experiments are also performed by illuminating the object with diffused light. A correlator using paraboloidal mirror segments as the Fourier-transforming element is also described.
Typical laser systems now available for atmospheric probing are summarized. Experiments comparing coherent and incoherent receiving techniques are described and typical performance data presented.
Discussion of the optimum power allocation problem associated with the design of a phase-coherent receiver employing a bandpass limiter. A single channel system is treated in detail, and an optimization technique is proposed that makes use of up-to-date phase-locked loop and bandpass limiter theories recently contributed by Lindsey (1969) and Springett and Simon (1971). It is shown how this technique can be extended to a two-channel system.