Showing papers on "Clock synchronization published in 1981"
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IBM1
TL;DR: In this article, a method and a device for effecting the initial adjustment of the clock during a turn-on period in the course of which the receiver is supplied with a known clock synchronization signal followed by a known equalizer training sequence is presented.
Abstract: In a synchronous data receiver that includes a clock and an adaptive equalizer, a method and a device for effecting the initial adjustment of the clock during a turn-on period in the course of which the receiver is supplied with a known clock synchronization signal followed by a known equalizer training sequence. In accordance with the method of invention, the incoming signal is sampled and the samples so obtained are stored in a storage means. The synchronization signal and the beginning of the training sequence are successively detected. When the beginning of the training sequence is detected, the storage locations for the samples of the received synchronization signal are known and a control signal controlling the initial adjustment of the clock is derived from these samples, which are stored in predetermined locations in the storage means. In a preferred embodiment of the invention, said control signal is derived from the samples that precede the G samples immediately followed by the beginning of the training sequence, the value of G being such that those samples which are in the vicinity of the transition region between the synchronization signal and the training sequence will not be used.
34 citations
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18 Dec 1981
TL;DR: A clock synchronization system for use in a digital switching system including multiple clock circuits is described in this paper, where a clock synchronization circuit includes a counter chain which provides a periodic system framing pulse and a trigger circuit which insures that its slave system framer is in synchronization with the master system.
Abstract: A clock synchronization system for use in a digital switching system including multiple clock circuits. This circuit includes multiple synchronization circuits connected in a master-slave arrangement. Each synchronization circuit includes a counter chain which provides a periodic system framing pulse and a trigger circuit which insures that its slave system framing pulse is in synchronization with the master system framing pulse.
27 citations
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30 Nov 1981TL;DR: In this article, a microprocessor based, digital to digital converting, full duplex time division multiplexing data set operating in burst mode transmission interfaces a data terminal to a communication path for communicating with another data terminal.
Abstract: A microprocessor based, digital to digital converting, full duplex time division multiplexing data set operating in burst mode transmission interfaces a data terminal to a communication path for communicating with another data terminal. The data set includes a transmitter, a receiver, a controlled transmit/receive switch, digital logic control circuitry, and a microprocessor for communicating with and controlling the other elements thereof. Communication is based on a bipolar code, and bipolar violation encoding is used to signal special messages. Control words, indicated by bipolar violations, are generated within one data set and transmitted to another data set as a preamble to a bipolar violation for communicating information to, and controlling operation of, the other data set. Special start and stop bits are generated by the data set before and after each fixed length data block for clock synchronization and DC balancing, and are stripped from the data clock by the receiving data set. Circuitry is also provided for generating a DC balance bit within each preamble to a bipolar violation. Specific logic circuits and control programs cooperate in providing system operation.
10 citations
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TL;DR: N integrated digital network which combines digital transmission and switches can provide efficient and economical paths to carry analog and digital information.
Abstract: N integrated digital network which combines digital transmission and switches can provide efficient and economical paths to carry analog ~ and digital information. Digital networks have been developed for data or voice services, and it is believed that they may be extended in the future to apply to the integrated services digital network (ISDN). Network synchronization is an essential technique in constructing an integrated digital network. In several countries, the domestic network synchronization systems have either been developed or are under development, These systems employ either the master-slave or mutual synchronization scheme. For the future international digital network, plesiochronous operation is recommended by the CCITT.
8 citations
15 Dec 1981
TL;DR: In this article, the form and flow of information from signal reception to recorded bits at each station, through cross-correlation, phase-tracking, phase calibration, and bandwidth synthesis, to final observable formation are traced.
Abstract: The form and flow of information from signal reception to recorded bits at each station, through cross-correlation, phase-tracking, phase calibration, and bandwidth synthesis, to final observable formation are traced. In this process the data volume is greatly compressed for each observation, from approx. 10 to the 9th power bits on the station tapes to only four final observables: amplitude, delay, phase-delay rate and RF phase. After phase calibration and propagation media calibrations, the final delay observable is shown to be the sum of a geometric delay and a clock synchronization offset.
5 citations
01 Mar 1981
TL;DR: A two-way time synchronization experiment performed in the spring of 1979 and 1980 via the Italian SIRIO-1 experimental telecommunications satellite is described in this paper, where it is shown that the precision of the time synchronization is between 1 and 5 ns.
Abstract: A two-way time synchronization experiment performed in the spring of 1979 and 1980 via the Italian SIRIO-1 experimental telecommunications satellite is described. The experiment was designed and implemented to precisely monitor the satellite motion and to evaluate the possibility of performing a high precision, two-way time synchronization using a single communication channel, time-shared between the participating sites. Results show that the precision of the time synchronization is between 1 and 5 ns, while the evaluation and correction of the satellite motion effect was performed with an accuracy of a few nanoseconds or better over a time interval from 1 up to 20 seconds.
3 citations
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TL;DR: In this paper, a time synchronization system was developed for the Gulmarg-Srinagar coincidence experiment for detection of primordial blackhole explosions, which utilizes field-markers derived from the synchronization pulse train of Srinagar Television to match the station clocks and give a relative time accuracy of ⪕2 μs.
Abstract: A time synchronization system has been developed for the Gulmarg-Srinagar coincidence experiment for detection of primordial black-hole explosions. It utilizes field-markers derived from the synchronization pulse train of Srinagar Television to match the station clocks and give a relative time accuracy of ⪕2 μs. The epoch ambiguity with respect to the absolute time is determined to an accuracy of ⪕1 ms with the help of high frequency time signals from ATA and RWM. The system can presently be employed for the synchronization of remotely-located clocks through the radio time-signals. In future, it can be used for this purpose in the TV synchronization mode also when the national television hook-up becomes possible. The resulting synchronization accuracy of -1 μs should be sufficient for future very-long baseline coincidence experiments in γ-ray and radio astronomies and will dispense with the portable clock method of synchronization which in general, is not readily accessible.
2 citations
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01 Apr 1981TL;DR: A means of extracting clocking information using a lattice linear predictor on a received digital data stream, such as seen from a recording channel, that accurately follows the transient behavior of the digital symbols and isolates the symbols to form a sync signal suitable for driving a phase-locked-loop.
Abstract: An interest in the application of communication techniques to the recovery of information from magnetic recording has lead to an investigation of clock synchronization for these channels. The work presented here demonstrates a means of extracting clocking information using a lattice linear predictor on a received digital data stream, such as seen from a recording channel. The lattice linear predictor accurately follows the transient behavior of the digital symbols and isolates the symbols to form a sync signal suitable for driving a phase-locked-loop. The supression of noise using this technique enables the bandwidth of the locked oscillator to be sufficient to allow rapid tracking of the varying data rate associated with magnetic readback signals.
2 citations
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TL;DR: The world-wide Deep Space Network (DSN), with facilities in the United States, Spain, and Australia, uses atomic frequency standards to generate stable frequency and timing signals to meet the telemetry and tracking requirements for space exploration missions.
Abstract: The world-wide Deep Space Network (DSN), with facilities in the United States, Spain, and Australia, uses atomic frequency standards to generate stable frequency and timing signals to meet the telemetry and tracking requirements for space exploration missions. Outer planet navigation requires doppler accuracy of 30 micrometers per second, range accuracy of two meters, angle accuracy of a few nanoradians (using Very Long Baseline Interferometry (VLBI) techniques), and high reliability. These needs impose stability requirements on frequency standards of parts in 1014 over several hours and 1012 at one second. In addition, a low drift rate is necessary so as to minimize the number of measurements needed to maintain clock synchronization to 100 nanoseconds and frequency syntonization to 3 x 10-13 between the three complexes. The Jet Propulsion Laboratory (JPL), which operates the DSN for the National Aeronautics and Space Administration (NASA), uses ensembles of active hydrogen masers, cesium beam frequency standards, and high resolution clocks to achieve the required performance reliably. Time synchronization between complexes is currently achieved by the use of VLBI techniques, traveling clocks, and Loran-C. Use of the Global Positioning Satellites (GPS) is under active investigation as a less costly and more accurate alternative. This article covers the above requirements, equipment, techniques, and more stringent requirements of the 1990 time frame.
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TL;DR: In this paper, two Cs-atomic clocks, one located in Raisting (Federal Republic of Germany) and the other in Nanjing (China) were compared from June 18 to 27, 1979, via SYMPHONIE satellite using two-way relay noncoherent time-transfer technique.
Abstract: Clock synchronization experiment between ground stations in Beijing and Shanghai and also between Nanjing and Shanghai were carried out in March, 1979, by the National Institute of Metrology of China. Based on the results of this experiment, two Cs-atomic clocks, one located in Raisting (Federal Republic of Germany) and the other in Nanjing (China) were compared from June 18 to 27, 1979, via SYMPHONIE satellite using two-way relay noncoherent time-transfer technique. The experimental results showed that an accuracy of 80 ns was achieved for the clock synchronization with a random fluctuation of about 10 ns. These results were confirmed by the use of a portable clock.
01 Mar 1981
TL;DR: In this paper, the effects of source structure on radio interferometry measurements were investigated and the brightness distribution measurements for ten extragalactic sources were analyzed, and significant results were reported.
Abstract: The effects of source structure on radio interferometry measurements were investigated. The brightness distribution measurements for ten extragalactic sources were analyzed. Significant results are reported.
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13 Jan 1981
TL;DR: In this paper, the authors proposed to realize both characteristics of high-speed clock synchronization and phase jitter suppression to eliminate effectively troubles of the time division multiple access system and so on, by switcing two different reproducing clocks of a clock reproducing circuit.
Abstract: PURPOSE:To realize both characteristics of high-speed clock synchronization and phase jitter suppression to eliminate effectively troubles of the time division multiple access system and so on, by switcing two different reproducing clocks of a clock reproducing circuit. CONSTITUTION:Input signal Si including clock components is branched into two by branching circuit 21, and one signal Si1 is applied to wide band filter 22 to extract clock components D, and amplitude fluctuation components of components D are eliminated by amplitude limiter 24, and the output of lmiter 24 is applied to switch 27. The other signal Si2 separated by circuit 21 is applied to narrow band filter 23 to extract clock components E, and amplitude fluctuation components of components E are eliminated by amplitude limiter 25, and the output of limiter 25 is applied to switch 27. Components D obtained by branching input signal Si into two are detected by detector 26, and the detected control signal is applied to swotch 27 where outputs of limiters 24 and 25 are input, and output signal So of switch 27 is switched from reproducing clock So1 or So2 to reproducing clock So2 or So1 by the control signal.