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  • 1
    Publication Date: 1977-04-01
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
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  • 2
    Publication Date: 2011-08-19
    Description: A technique for maintaining synchronization between optical PPM (pulse-position modulation) pulses and a receiver clock by means of a delay-tracking loop is described and analyzed. The tracking loop is driven by a doubly stochastic Poisson process that contains information about the location of the desired slot boundaries. The slot boundaries are subject to slowly varying random delays that are ultimately tracked by the loop. The concept of fractional rms delay error is introduced to quantify the effects of signal and background induced shot noise on the performance of the delay-tracking loop.
    Keywords: COMMUNICATIONS AND RADAR
    Format: text
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  • 3
    Publication Date: 2011-08-19
    Description: Demonstration results are presented for a high dynamic GPS receiver. The receiver tested is a breadboard unit capable of tracking one simulated satellite signal in pseudorange and range rate. The receiver makes approximate maximum likelihood estimates of pseudorange and range rate each 20 ms, and tracks these observables using a third order filter with a time constant of 0.14 s. Carrier phase is not tracked, which eliminates the typical failure mode of loss of carrier lock associated with PLLs at high dynamics. The receiver tracks with pseudorange lag errors of under 0.06 m when subjected to simulated 50 g turns with 40 g/s peak jerk. Pseudorange errors due to receiver noise alone are approximately 0.6 m rms at a carrier power to noise spectral density ratio of 34 dB-Hz. The tracking threshold SNR is approximately 28 dB-Hz, which provides 12 dB margin relative to the 40 dB-Hz that occurs with minimum specified satellite signal strength, 3.5 dB system noise figure, and 0 dBi antenna gain.
    Keywords: AIRCRAFT COMMUNICATIONS AND NAVIGATION
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  • 4
    Publication Date: 2013-08-31
    Description: A real-time digital signal combining system for use with Ka-band feed arrays is proposed. The combining system attempts to compensate for signal-to-noise ratio (SNR) loss resulting from antenna deformations induced by gravitational and atmospheric effects. The combining weights are obtained directly from the observed samples by using a sliding-window implementation of a vector maximum-likelihood parameter estimator. It is shown that with averaging times of about 0.1 second, combining loss for a seven-element array can be limited to about 0.1 dB in a realistic operational environment. This result suggests that the real-time combining system proposed here is capable of recovering virtually all of the signal power captured by the feed array, even in the presence of severe wind gusts and similar disturbances.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommunications and Data Acquisition Report; p 81-99
    Format: application/pdf
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  • 5
    Publication Date: 2011-08-17
    Description: The problem of spatially acquiring an optical beacon in the presence of intense optical interference is considered. It is demonstrated that conventional acquisition procedures cannot establish acceptable levels of acquisition probability when competing with strong optical interference without requiring unreasonable amounts of prime power. As a possible solution, it is shown that a more sophisticated acquisition scheme can virtually eliminate the effects of optical interference while requiring only a modest increase in system complexity.
    Keywords: OPTICS
    Type: The Telecommun. and Data Acquisition Rept.; p 91-96
    Format: text
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  • 6
    Publication Date: 2011-08-18
    Description: Optical communications systems operating over interplanetary distances require the use of extremely narrow optical beams for maximum power concentration near the receiver. Consequently, pointing errors must be kept to a small fraction of a beamwidth to avoid severe deterioration in receiver performance, due to the decrease in received power associated with pointing errors. Mathematical moels required for studying the effects of random pointing errors were developed and applied to the problem of quantifying the effects of pointing errors on the performance of coherent and incoherent optical receivers.
    Keywords: OPTICS
    Type: The Telecommun. and Data Acquisition Rept.; p 136-146
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  • 7
    Publication Date: 2011-08-18
    Description: The structure of a coherent binary optical MAP receiver was derived and the effects of background radiation and phase estimation errors on receiver performance were evaluated. It was found that random phase errors do not affect the performance of the coherent receiver significantly, as long as the standard deviation of the phase error remains less than roughly 0.14 radians (or 8 degrees). It was also shown that background radiation is effectively suppressed by the optical homodyne receiver: Significant deterioration in receiver performance is observed only in the presence of extremely intense background fields. The most notable characteristic of the binary optical homodyne receiver therefore appears to be its ability to achieve quantum limited performance in high background environments, provided that sufficiently accurate estimates of the received phase can be obtained.
    Keywords: OPTICS
    Type: The Telecommun. and Data Acquisition; p 27-38
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  • 8
    Publication Date: 2011-08-19
    Description: The structure of a maximum a posteriori decoder is derived for binary optical fields processed according to Kennedy's near-optimum scheme, but operating in the presence of random optical phase-error and interfering background fields. An exact expression is found for the error probability, and examples to illustrate decoder performance under various operating conditions of interest are provided.
    Keywords: CYBERNETICS
    Type: IEEE Transactions on Information Theory (ISSN 0018-9448); IT-30; 446-450
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  • 9
    Publication Date: 2018-06-08
    Description: In this article, they describe a novel adaptive optical array receiver designed to improve ground-based reception of optical signals.
    Type: IPN-ISN Technology and Science News
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  • 10
    Publication Date: 2018-06-08
    Description: A real-time array feed compensation system has been constructed, and is currently undergoing tests at JPL.
    Keywords: Communications and Radar
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