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Automatic frequency control of satellite transmitted spread spectrum signals

  • US 5,036,523 A
  • Filed: 10/03/1989
  • Issued: 07/30/1991
  • Est. Priority Date: 10/03/1989
  • Status: Expired due to Term
First Claim
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1. A radio communication system, comprising:

  • a remote transmitter for transmitting a burst mode, direct sequence spread spectrum information signal having a carrier center frequency F1, a chip frequency α

    , and a power versus frequency spectrum characterized by at least one intermediate null frequency at which the signal power has a minimum value, said null frequency occurring at F1 ±



    , where K is an integer equal to or greater than 1;

    a central station having a pilot signal transmitter for transmitter a pilot signal in the form of a continuous unmodulated carrier signal having a frequency substantially equal to said null frequency, and a receiver for receiving retransmitted information and pilot signals;

    a signal relay for receiving the information signal from said remote transmitter and the pilot signal from said central station, and for retransmitting said information and pilot signals to the central station, said signal relay including a local oscillator which is susceptible to frequency drift; and

    automatic frequency control means coupled to the receiver at said central station for detecting variations in the frequency of the received pilot signal and for adjusting the response of the receiver in accordance with said variations.

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