Frequency translation correction scheme for satellite communication system
First Claim
1. For use with a communication system having a first station for transmitting message signals over a communications link to a second station, said communications link subjecting signals transmitted thereover to a modification of a characteristic thereof, a method of enabling message signals transmitted from said first station to be received at said second station without said characteristic modification so that the information contained there in may be recovered at said second station comprising the steps of:
- at said first station,(a) transmitting a signal over the communications link for reception by the first station;
(b) monitoring the signal received in step (a) relative to said transmitted signal to determine said modification of a characteristic of signals transmitted over said communications link;
(c) subjecting message signals, comprising information not related to any portion of said modification of a characteristic of signals over said communications link, to a premodification of said characteristic thereof that is effectively complementary to the monitored modification of the characteristic of signals by said communications link, so that, when transmitted over said communications link from said first station to said second station, message signals that have been premodified are received by said second station effectively free of the modifications imparted by the first station and said communications link; and
(d) at the second station, determining a preselected characteristic of the received message signals and controlling a preselected characteristic of message signals to be transmitted from the second station to the first station using the determined preselected characteristic of the received message signals.
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Abstract
In a time division multiple access satellite communications system having a master station and one or more remote stations, frequency offset through the translation oscillator in the satellite is corrected by transmitting a pilot frequency signal, reference to a high precision oscillator, through the satellite, so as to subject the pilot frequency signal to a frequency translation and monitoring the frequency translation of the pilot frequency signal as received at the master station subsequent to its transmission through the satellite. Signals to be transmitted over the satellite communications link from the master station to remote stations are subjected to a frequency translation that is effectively complementary to the monitored frequency translation. At a remote station, received signals are monitored for a difference in the corrected frequency (base upon the use of the precision oscillator at the master site) relative to a prescribed frequency and signals to be transmitted from the remote station to the master station are adjusted by an amount that effectively compensates for the difference between the prescribed frequency and the monitored frequency.
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Citations
32 Claims
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1. For use with a communication system having a first station for transmitting message signals over a communications link to a second station, said communications link subjecting signals transmitted thereover to a modification of a characteristic thereof, a method of enabling message signals transmitted from said first station to be received at said second station without said characteristic modification so that the information contained there in may be recovered at said second station comprising the steps of:
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at said first station, (a) transmitting a signal over the communications link for reception by the first station; (b) monitoring the signal received in step (a) relative to said transmitted signal to determine said modification of a characteristic of signals transmitted over said communications link; (c) subjecting message signals, comprising information not related to any portion of said modification of a characteristic of signals over said communications link, to a premodification of said characteristic thereof that is effectively complementary to the monitored modification of the characteristic of signals by said communications link, so that, when transmitted over said communications link from said first station to said second station, message signals that have been premodified are received by said second station effectively free of the modifications imparted by the first station and said communications link; and (d) at the second station, determining a preselected characteristic of the received message signals and controlling a preselected characteristic of message signals to be transmitted from the second station to the first station using the determined preselected characteristic of the received message signals. - View Dependent Claims (2, 3)
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4. For use in a communication system wherein message signals are transmitted between first and second stations over a communications link that subjects signal modification of a characteristic thereof, a method of communicating between said first and second stations over said communications link in the presence of said modification comprising the steps of:
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at said first station, (a) transmitting a signal over the communications link for reception by the first station and monitoring the received signal relative to the transmitted signal to determine said modification of a characteristic of signals transmitted over said communications link; (b) subjecting message signals to be transmitted over said communications link from said first station to said second station to a premodification of said characteristic thereof that is effectively complementary to the monitored modification of step (a); and (c) transmitting message signals, which carry information not related to the determined modification of a characteristic of signals transmitted over the communications link that have been subjected to a premodification with the complementary characteristic in step (b) over said communications link to said second station; and at said second station (d) receiving the premodified message signals that have been transmitted over said communications link from said first station in step (c) effectively free of the modification imparted by said (b) and the communications link, and determining therefrom a preselected characteristic of the received message signals; (e) controlling a preselected characteristic of message signals to be transmitted over said communications link from said second station to said first station using the preselected characteristic determined from the message signals received in step (b); and (f) transmitting message signals, a preselected characteristic of which is controlled in step (e), from said second station over said communications link to said first station. - View Dependent Claims (5, 6, 7, 8, 9, 10)
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11. For use in a satellite communication system wherein message signals are transmitted between first and second earth stations over a satellite communications link containing a communications satellite that subjects signals transmitted therethrough to a frequency translation, a method of communicating between said first and second stations over said communications link in the presence of said frequency translation comprising the steps of:
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at said first station, (a) transmitting a pilot frequency signal through said communications satellite so as to subject said pilot frequency to said frequency translation and monitoring the frequency translation of said pilot frequency signal as received at said first station subsequent to its transmission through said communications satellite; (b) subjecting message signals, which comprise information not related to said monitored frequency translation monitored in step (a), to be transmitted over said communication link from said first station to said second station to a frequency translation that is effectively complementary to the frequency translation monitored in step (a); and (c) transmitting message signals that have been subjected to the complementary frequency translation of step (b) over said communications link to said second station; and at said second station, (d) receiving the message signals that have been transmitted in step (c) over said communications link from said first station, which received message signals are effectively free of any frequency translation imparted by the first station and the communications link, and determining therefrom a preselected characteristic; (e) controlling a preselected characteristic of message signals to be transmitted over said communications link from said second station to said first station using the preselected characteristic determined in step (d); and (f) transmitting message signals, a preselected characteristic of which is controlled in step (e), from said second station over said communications link to said first station. - View Dependent Claims (12)
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13. For use in a satellite communications system wherein signals are transmitted between a master station and a plurality of remote stations over satellite communications links containing a communications satellite that subjects signals transmitted therethrough from said master station to one of said remote stations to a first frequency translation, a method of communicating between said master and remote stations over said satellite communications links in the presence of said first and second frequency translations comprising the steps of:
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at said master station, (a) transmitting a pilot frequency signal through said communications satellite so as to subject said pilot frequency signal to said first frequency translation and monitoring the frequency translation of said pilot frequency signal as received at said master station subsequent to its transmission through said communications satellite; (b) subjecting message signals, comprising information not related to said monitored frequency translation, to be transmitted over said satellite communications link from said master station to said one of said remote stations to a frequency translation that is effectively complementary to the frequency translation monitored in step (a); and (c) transmitting the message signals that have been subjected to the complementary frequency translations of step (b) over said satellite communications link to said one of said remote stations; and at said one of said remote stations, (d) receiving signals that have been transmitted over said communications link from said master station in step (c) effectively free of the frequency translation imparted by step (b) and said satellite communications link, and determining therefrom a preselected characteristic of the received message signal; (e) controlling a preselected characteristic of message signals to be transmitted over said communications link from said one remote station to said master station using the preselected characteristic determined from the message signals received in step (d); and (f) transmitting message signals, a preselected characteristic of which is controlled in step (e), from said one remote station over said communications link to said master station. - View Dependent Claims (14)
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15. For use in a satellite communications system wherein signals are transmitted between a master station and a plurality of remote stations over satellite communications links containing a communications satellite that subjects signals transmitted therethrough from said master station to said remote stations to a first frequency translation, a method of communicating between said master and remote stations over said satellite communications links in the presence of said first and second frequency translations comprising the steps of:
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at said master station, (a) transmitting a pilot frequency signal through said communications satellite so as to subject said pilot frequency signal to said first frequency translation and monitoring the frequency translation of said pilot frequency signal as received at said master station subsequent to its transmission through said communications satellite; (b) subjecting message signals, comprising information not related to said monitored frequency translation, to be transmitted over said satellite communications link from said master station to said remote stations to a premodification of a frequency translation that is effectively complementary to the frequency translation monitored in step (a); and (c) transmitting message signals that have been subjected to a premodification with the complementary frequency translation of step (b) over said satellite communications link to said remote stations; and at said remote stations, (d) receiving the premodified message signals that have been transmitted over said communications link from said master station in step (c) effectively free of the modification imparted by said master station and communications satellite, and determining therefrom a preselected characteristic of the received message signal; (e) controlling a preselected characteristic of message signals to be transmitted over said communications link from said one remote station to said master station using the preselected characteristic determined from the message signals received in step (d); and (f) transmitting message signals, a preselected characteristic of which is controlled in step (e), from said remote stations over said communications link to said master station. - View Dependent Claims (16)
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17. For use with a communication system having a first station for transmitting signals over a communication link to a second station, said communication link subjecting signals transmitted thereover to a modification of a characteristic thereof, an arrangement for enabling signals transmitted from said first station to be received at said second station without said characteristic modification so that information contained there may be recovered at said second station comprising:
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at said first station, first means for transmitting a signal over the communication link for reception by the first station and monitoring said modification of a characteristic of signals transmitted over said communication link; and second means for subjecting message signals, comprising information not related to said modification of a characteristic of signals, to be transmitted from said first station to said second station to a premodification of said characteristic thereof that is effectively complementary to the monitored modification of a characteristic of signals imparted by said communication link, so that, when transmitted over said communication link from said first station to said second station, signals that have been premodified are received by said second station effectively free of the modification imparted by said communication link. - View Dependent Claims (18, 19)
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20. For use in a communication system wherein message signals are transmitted between first and second stations over a communications link that subjects signal modification of a characteristic thereof, an arrangement for communicating between said first and second stations over said communications link in the presence of said modification comprising:
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at said first station, first means for transmitting a signal over the communications link for reception by the first station and monitoring said modification of a characteristic of signals transmitted over said communications link; and second means for subjecting message signals, comprising information not related to said monitored modification of a characteristic of signals, to be transmitted over said communications link from said first station to said second station to a premodification of said characteristic thereof that is effectively complementary to the monitored modification by the first means; at said second station, third means for receiving message signals that have been premodified by the second means and transmitted over said communications link from said first station effectively free of the modification imparted by the second means and the communications link and for determining therefrom a preselected characteristic of the received signal; fourth means for controlling a preselected characteristic of message signals to be transmitted over said communications link from said second station to said first station using the preselected characteristic determined by the third means from message signals received by said third means; and fifth means for transmitting message signals, a preselected characteristic of which is controlled by said fourth means, from said second station over said communications link to said first station. - View Dependent Claims (21, 22, 23, 24, 25, 26)
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27. For use in a satellite communication system wherein message signals are transmitted between first and second earth stations over a satellite communications link containing a communications satellite that subjects signals transmitted therethrough to a frequency translation, an arrangement for communicating between said first and second stations over said communications link in the presence of said frequency translation comprising:
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at said first station, first means for transmitting a pilot frequency signal through said communications satellite so as to subject said pilot frequency signal to said frequency translation and monitoring the frequency translation of said pilot frequency signal as received at said first station subsequent to its transmission through said communications satellite; second means for subjecting message signals, comprising information not related to the monitored frequency translation by the first means, to be transmitted over said communications link from said first station to said second station to a frequency translation that is effectively complementary to the frequency translation monitored by said first means; and third means for transmitting message signals that have been subjected to the complementary frequency translation of said second means over said communications link to said second station; and at said second station, fourth means for receiving message signals that were subjected to the complementary frequency translation by said second means, and have been transmitted over said communications link from said first station, effectively free of the frequency translation imparted by said second means and the communications link, and for determining therefrom a preselected characteristic of the received signal; fifth means for controlling a preselected characteristic of message signals to be transmitted over said communications link from said second station to said first station using the preselected characteristic determined by the fourth means from message signals received by said fourth means; and sixth means for transmitting message signals, a preselected characteristic of which is controlled by said fifth means, from said second station over said communications link to said first station. - View Dependent Claims (28)
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29. For use in a satellite communications system wherein signals are transmitted between a master station and a plurality of remote stations over satellite communications links containing a communications satellite that subjects signals transmitted therethrough from said master station to one of said remote stations to a first frequency translation, an arrangement for communicating between said master and remote stations over said satellite communications links in the presence of said first and second frequency translations comprising:
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at said master station, first means for transmitting a pilot frequency signal through said communications satellite so as to subject said pilot frequency signal to said first frequency translation and monitoring the frequency translation of said pilot frequency signal as received at said master station subsequent to its transmission through said communications satellite; second means for subjecting message signals, comprising information not related to the monitored frequency translation by the first means, to be transmitted over said satellite communications link from said master station to said one of said remote stations to a frequency translation that is complementary to the frequency translation monitored by said first means; and third means for transmitting message signals that have been subjected to the complementary frequency translation of said second means over said satellite communications link to said one of said remote stations; and at said one of said remote stations, fourth means for receiving message signals, that have been transmitted over said communications link from said master station by said third means, effectively free of any frequency translation imparted by the second means and the communications satellite for determining therefrom a preselected characteristic of the received signals; fifth means for controlling a preselected characteristic of message signals to be transmitted over said communications link from said one remote station to said master station using the preselected characteristic determined by said fourth means; and sixth means for transmitting signals, a preselected characteristic of which is controlled by said fifth means, from said one remote station over said communications link to said master station. - View Dependent Claims (30)
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31. For use in a satellite communications system wherein signals are transmitted between a master station and a plurality of remote stations over satellite communications links containing a communications satellite that subjects signals transmitted therethrough from said master station to said remote stations to a first frequency translation an arrangement for communicating between said master and remote stations over said satellite communications links in the presence of said first and second frequency translations comprising:
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at said master station, first means for transmitting a pilot frequency signal through said communications satellite so as to subject said pilot frequency signal to said first frequency translation and monitoring the frequency translation of said pilot frequency signal as received at said master station subsequent to its transmission through said communications satellite; second means for subjecting message signals, comprising information not related to the monitored frequency translation by the first means, to be transmitted over said satellite communications link from said master station to said remote stations to a frequency translation that is effectively complementary to the frequency translation monitored by said first means; and third means for transmitting message signals, that have been subjected to the complementary frequency translation of said second means, over said satellite communications link to said remote stations; and at said remote stations, fourth means for receiving premodified message signals that have been transmitted over said communications link by the third means at said master station effectively free of the frequency translation imparted by said third means and said satellite communications link, and determining therefrom a preselected characteristic of the received message signal; fifth means for controlling a preselected characteristic of signals to be transmitted over said communications link from said one remote station to said master station using the preselected characteristic determined from the message signals received by said fourth means; and sixth means for transmitting message signals, a preselected characteristic of which is controlled by said fifth means, from said remote stations over said communications link to said master station. - View Dependent Claims (32)
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Specification