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AssigneeCommunications Satellite Corporation (Comsat)
InventorChester Joseph Wolejsza, Jr.
Estimating the term…
A pilot signal for implementing automatic frequency control in a satellite communications system is continuously transmitted by a designated ground station. Its frequency lies in the middle of the communications band so that it will undergo the same frequency shifts or distortions as the overall communications signal. A second ground station monitors the presence of the pilot signal, and if it is lost for a predetermined time, this second station then transmits the pilot signal to ensure the continuation of the AFC function throughout the system. If the pilot signal is lost at the second station, however, an uncertainty might exist as to whether the failure is in the designated ground station or the second ground station. To resolve this uncertainty a secondary pilot signal, having a frequency different from but in the same band as the primary pilot signal, is transmitted by a third ground station. If the second station then looses the primary pilot signal while still receiving the secondary pilot signal, it knows that the failure is in the designated ground station and therefore begins to transmit the pilot signal. A fourth ground station may monitor both the primary and secondary pilot signals, and transmit the secondary pilot signal if the latter is lost while the primary pilot signal is still being received, thus providing a back-up capability for the secondary pilot signal.
In a satellite communications system including a plurality of ground stations for transmitting and receiving signals within a designated communications band, a satellite repeater for receiving all transmitted signals and retransmitting them back to all ground stations, and means at a first ground station for transmitting a primary pilot signal for implementing an automatic frequency control function at all ground stations, the improvements comprising:
In a satellite communications system including a plurality of ground stations for transmitting and receiving signals within a designated communications band, a satellite repeater for receiving all transmitted signals and retransmitting them back to all ground stations, and means at a first ground station for transmitting a primary pilot signal for implementing an automatic frequency control function at all ground stations, a method of resolving uncertainties as to the source of a malfunction resulting in the loss of the primary pilot signal, comprising the steps of:
Dependencies are inferred from the claim text.