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METHOD AND APPARATUS FOR SYNCHRONIZING THE TRANSMISSION OF DIGITAL SIGNALS BETWEEN GROUND STATIONS VIA A COMMUNICATIONS SATELLITE

  • US 3,646,444 A
  • Filed: 10/08/1969
  • Issued: 02/29/1972
  • Est. Priority Date: 10/16/1968
  • Status: Expired due to Term
First Claim
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1. A method for synchronizing the time-division multiplex transmission of digital data signals via a satellite between a plurality of ground stations, one of which is a reference station, comprising the steps of:

  • a. generating at the reference station a signal having a fixed frequency constituting a basic reference frequency for such transmission and transmitting reference bursts of this fixed frequency from the reference station to the satellite;

    b. receiving these reference bursts from the satellite at a second ground station;

    c. generating at such second ground station a local reception control signal whose frequency is substantially equal to such fixed frequency;

    d. electronically comparing, at such second station, the phase of the received reference bursts with the phase of the local reception control signal;

    e. varying, on the basis of such comparison, the local reception control signal in a direction to eliminate the phase difference between the received reference bursts and the local reception control signal, whereby the local reception control signal provides a reference for processing the data signals received by the second station;

    f. generating at the second station a local transmission control signal and transmitting local reference bursts of this signal to the satellite;

    g. receiving these local reference bursts back from the satellite at the second station;

    h. electronically comparing, at the second station, the phase of the local reference bursts received back from the satellite with the phase of the local reception control signal; and

    i. varying the local transmission control signal in a direction to eliminate the phase difference, at the second station, between the received local reference bursts and the local reception control signal, whereby the local transmission control signal provides a reference for transmitting, from the second station, data which will arrive at the satellite coherently with data transmitted from the reference station.

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