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Frequency acquisition method for direct sequence spread spectrum systems

  • US 5,799,034 A
  • Filed: 12/06/1995
  • Issued: 08/25/1998
  • Est. Priority Date: 12/06/1995
  • Status: Expired due to Term
First Claim
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1. In a direct sequence spread spectrum communications system having a master device and a slave device wherein the master device establishes a communications link with the slave device, a frequency acquisition device comprising:

  • acquisition frame message comprising an ID word transmitted by the master device and received by the slave device;

    dot product demodulation means for determining the dot product of the received acquisition frame message;

    cross product demodulation means for determining the cross product of the received acquisition frame message;

    receive clock generating means for generating receive timing control in the slave device;

    ID word detect means for detecting when the ID word has been demodulated by the dot product demodulation means and outputting a dot product detect signal and for detecting when the ID word has been demodulated by the cross product demodulation means and outputting a cross product detect signal;

    frame timing adjust means for adjusting the timing of the receive clock generating means to coincide with a time interval of the ID word when the ID detect means outputs a dot product detect signal; and

    means for outputting a frequency error estimate based on the values of the dot product and cross product detect signals and updating an automatic frequency control circuit.

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