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Spread spectrum communications system

  • US 5,121,407 A
  • Filed: 09/27/1990
  • Issued: 06/09/1992
  • Est. Priority Date: 09/27/1990
  • Status: Expired
First Claim
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1. A method of transmitting digital data, comprising the steps of:

  • a) generating a high frequency carrier at a first carrier frequency;

    b) modulating the frequency of said carrier with data bits assembled in data packets of predetermined format;

    c) generating a high frequency carrier at a first carrier frequency and shifting the nominal frequency of said carrier by a frequency increment DF to obtain a second carrier frequency, whereDF=K*1/Ts+dF,dF=approximately L/(2*Ts),K is an integer,L is an odd integer, andTs is a PN (pseudo noise) sequence period;

    d) modulating the frequency of said carrier in step c) with said data bits assembled in data packets of said predetermined format;

    e) spreading said carrier at said first and said second frequency, during a transmission time, by a predetermined PN sequence having a period Ts related to a bit time Tb whereTb=N * Ts, N being an integer >

    1 whereby a spread carrier spectrum comprising many spectral components separated by 1/Ts is obtained, the amplitudes of said components being reduced by said spreading function, said components and the modulation imposed upon them being separable from other components by a narrow band filter.

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