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  • 1
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    Spacecraft signal sources portable test system (1993)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: There is a frequent need to measure the frequency stability and phase noise levels of very high performance signal sources that are required for certain spacecraft missions. These measurements need to be done at different locations as the spacecraft subsystems progress through the various stages of development, assembly, test, and integration. Allan Deviation and Phase Noise of high performance sources are generally measured by comparing the unit under test to a reference standard. Five basic requirements are associated with making these kind of measurements: (1) the reference standard performance needs to be equal or better than the unit under test; (2) the measurement system needs to accommodate odd, nonstandard measurement frequencies that can range from 4 MHz to 35 GHz; (3) warm-up frequency drift and aging can corrupt a measurement and must be dealt with; (4) test equipment generated noise must be understood and prevented from limiting the measurements; (5) test equipment noise performance must be verifiable in the field as needed. A portable measurement system that was built by JPL and used in the field is described. The methods of addressing the above requirements are outlined and some measurement noise floor values are given. This test set was recently used to measure state of the art crystal oscillator frequency standards on the TOPEX and MARS OBSERVER spacecraft during several stages of acceptance tests.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA. Goddard Space Flight Center, The 24th Annual Precise Time and Time Interval (PTTI) Applications and Planning Meeting; p 427-438
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    A wide-band fiber optic frequency distribution system employing thermally controlled phase compensation (1993)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: An active wide-band fiber optic frequency distribution system employing a thermally controlled phase compensator to stabilize phase variations induced by environmental temperature changes is described. The distribution system utilizes bidirectional dual wavelength transmission to provide optical feedback of induced phase variations of 100 MHz signals propagating along the distribution cable. The phase compensation considered differs from earlier narrow-band phase compensation designs in that it uses a thermally controlled fiber delay coil rather than a VCO or phase modulation to compensate for induced phase variations. Two advantages of the wide-band system over earlier designs are (1) that it provides phase compensation for all transmitted frequencies, and (2) the compensation is applied after the optical interface rather than electronically ahead of it as in earlier schemes. Experimental results on the first prototype shows that the thermal stabilizer reduces phase variations and Allan deviation by a factor of forty over an equivalent uncompensated fiber optic distribution system.
    Keywords: PHYSICS (GENERAL)
    Type: NASA. Goddard Space Flight Center, The 24th Annual Precise Time and Time Interval (PTTI) Applications and Planning Meeting; p 365-374
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    NASA TECHNICAL REPORTS
  • 3
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    Zero-crossing detector with sub-microsecond jitter and crosstalk (1990)
    In:  Other Sources
    Details
    Publication Date: 2013-08-29
    Description: A zero-crossing detector (ZCD) was built and tested with a new circuit design which gives reduced time jitter compared to previous designs. With the new design, time jitter is reduced for the first time to a value which approaches that due to noise in the input amplifying stage. Additionally, with fiber-optic transmission of the output signal, crosstalk between units has been eliminated. The measured values are in good agreement with circuit noise calculations and approximately ten times lower than that for ZCD's presently installed in the JPL test facility. Crosstalk between adjacent units was reduced even more than the jitter.
    Keywords: PHYSICS (GENERAL)
    Type: The 22nd Annual Precise Time and Time Interval (PTTI) Applications and Planning Meeting; p 269-282
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    NASA TECHNICAL REPORTS
  • 4
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    An improved offset generator developed for Allan deviation measurement of ultra stable frequency standards (1992)
    In:  CASI
    Details
    Publication Date: 2013-08-29
    Description: Measuring the performance of ultra stable frequency standards such as the Superconducting Cavity Maser Oscillator (SCMO) necessitates improvement of some test instrumentation. The frequency stability test equipment used at JPL includes a 1 Hz Offset Generator to generate a beat frequency between a pair of 100 MHz signals that are being compared. The noise floor of the measurement system using the current Offset Generator is adequate to characterize stability of hydrogen masers, but it is not adequate for the SCMO. A new Offset Generator with improved stability was designed and tested at JPL. With this Offset Generator and a new Zero Crossing Detector, recently developed at JPL, the measurement flow was reduced by a factor of 5.5 at 1 second tau, 3.0 at 1000 seconds, and 9.4 at 10,000 seconds, compared against the previous design. In addition to the new circuit designs of the Offset Generator and Zero Crossing Detector, tighter control of the measurement equipment environment was required to achieve this improvement. The design of this new Offset Generator are described, along with details of the environment control methods used.
    Keywords: PHYSICS (GENERAL)
    Type: NASA. Goddard Space Flight Center, Proceedings of the 23rd Annual Precise Time and Time Interval (PTTI) Applications and Planning Meeting; p 209-21
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    NASA TECHNICAL REPORTS
  • 5
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    A Wide-band Fiber Optic Frequency Distribution System Employing (1993)
    In:  Other Sources
    Details
    Publication Date: 2018-06-08
    Format: text
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  • 6
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    (abstract) Precision Time and Frequency Transfer Utilizing SONET OC-3 (1996)
    In:  Other Sources
    Details
    Publication Date: 2018-06-08
    Description: An innovative method of distributing precise time and reference frequency to users located several kilometers from a frequency standard and master clock has been developed by the Timing Solutions Corporation of Boulder, CO. The Optical Two-Way Time Transfer System (OTWTTS) utilizes a commercial SONET OC-3 facility interface to physically connect a master unit to multiple slave units at remote locations. Optical fiber is a viable alternative to standard copper cable and microwave transmission. This paper discusses measurements of frequency and timing stability over the OTWTTS.
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  • 7
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    The 26th Annual Precise Time and Time Interval (PTTI) Applications and Planning Meeting (1995)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: This document is a compilation of technical papers presented at the 26th Annual PTTI Applications and Planning Meeting. Papers are in the following categories: (1) Recent developments in rubidium, cesium, and hydrogen-based frequency standards, and in cryogenic and trapped-ion technology; (2) International and transnational applications of Precise Time and Time Interval technology with emphasis on satellite laser tracking, GLONASS timing, intercomparison of national time scales and international telecommunications; (3) Applications of Precise Time and Time Interval technology to the telecommunications, power distribution, platform positioning, and geophysical survey industries; (4) Applications of PTTI technology to evolving military communications and navigation systems; and (5) Dissemination of precise time and frequency by means of GPS, GLONASS, MILSTAR, LORAN, and synchronous communications satellites.
    Keywords: PHYSICS (GENERAL)
    Type: NASA-CP-3302 , REPT-95B00083 , NAS 1.55:3302
    Format: application/pdf
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  • 8
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    Fiber optic frequency transfer link (1991)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A reference frequency distribution system is disclosed for transmitting a reference frequency from a reference unit to a remote unit while keeping the reference frequency at the reference unit and the remote unit in phase. A fiber optic cable connects the reference unit to the remote unit. A frequency source at the reference unit produces a reference frequency having an adjustable phase. A fiber optic transmitter at the reference unit modulates a light beam with the reference frequency and transmits the light beam into the fiber optic cable. A 50/50 reflector at the remote unit reflects a first portion of the light beam from the reference unit back into the fiber optic cable to the reference unit. A first fiber optic receiver disposed at the remote unit receives a second portion of the light beam and demodulates the reference frequency to be used at the remote unit. A second fiber optic receiver disposed at the reference unit receives the first portion of the light beam and demodulates a reference frequency component. A phase conjugator is connected to the frequency source for comparing the phase of the reference frequency component to the phase of the reference frequency modulating the light beam being transmitted from the reference unit to maintain a conjugate (anti-symmetric) relationship between the reference frequency component and the reference frequency modulating the light beam where virtually no phase difference exists between the phase of the reference frequency component and the phase of the reference frequency modulating the light beam.
    Keywords: OPTICS
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 9
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    Precision Time and Frequency Transfer Utilizing SONET OC-3(sup 1) (1996)
    In:  Other Sources
    Details
    Publication Date: 2018-06-08
    Description: An innovative method of distributing precise time and reference frequency to users located several kilometers from a frequency standard and master clock has been developed.
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    NASA TECHNICAL REPORTS
  • 10
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    The 25th Annual Precise Time and Time Interval (PTTI) Applications and Planning Meeting (1994)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Papers in the following categories are presented: recent developments in rubidium, cesium, and hydrogen-based frequency standards, and in cryogenic and trapped-ion technology; international and transnational applications of precise time and time interval (PTTI) technology with emphasis on satellite laser tracking networks, GLONASS timing, intercomparison of national time scales and international telecommunication; applications of PTTI technology to the telecommunications, power distribution, platform positioning, and geophysical survey industries; application of PTTI technology to evolving military communications and navigation systems; and dissemination of precise time and frequency by means of GPS, GLONASS, MILSTAR, LORAN, and synchronous communications satellites.
    Keywords: PHYSICS (GENERAL)
    Type: AD-A280955 , NASA-CP-3267 , REPT-94B00063 , NAS 1.55:3267 , Nov 29, 1993 - Dec 02, 1993; Marina Del Rey, CA; United States
    Format: application/pdf
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