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Spectrum spread signal reception with differential demodulation of spectrum spread demodulated components at each synchronous point and at a point always one symbol period later

  • US 5,612,972 A
  • Filed: 12/28/1994
  • Issued: 03/18/1997
  • Est. Priority Date: 12/28/1993
  • Status: Expired due to Term
First Claim
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1. A spectrum spread receiving method of receiving a spectrum spread modulated signal transmitted from a spectrum spread transmitter for differential modulation of adjacent symbol data of a transmitter input signal into differential modulated components and for individually multiplying a spectrum spread code and said differential modulated components into spectrum spread modulated components of said spectrum spread modulated signal said spectrum spread receiving method includes the steps of receiving said spectrum spread modulated signal as reception components having a common symbol period, individually multiplying said spectrum spread code and said reception components into spectrum spread demodulated components, and output demodulating said spectrum spread demodulated components into differential demodulated components of a reproduction of said transmitter input signal, wherein said output demodulating step comprises the steps of:

  • tracking successive regions of a greater correlation value in said spectrum spread demodulated components to produce a timing signal indicative of synchronous points in said regions, respectively; and

    differential demodulating responsive to said timing signal said spectrum spread demodulated components into said differential demodulated components at each of said synchronous points and at a time which is always one symbol period later than each of said synchronous points,said spectrum spread code includes a predetermined number of chips having a common chip period equal to said symbol period divided by said predetermined number, wherein said tracking step comprises the steps of;

    leaky integrating an instantaneous amplitude, during an integral submultiple of said chip period, into integrated amplitudes produced in each of said regions and comprising maximum correlation values in said regions, respectively, wherein said instantaneous amplitude is an instantaneous amplitude which said spectrum spread demodulated components have above an amplitude threshold level as said greater correlation value, each maximum correlation value and a succeeding one of said maximum correlation values in a succeeding one of said regions having a value interval variable shorter and longer than said symbol period; and

    generating responsive to said maximum correlation values said timing signal.

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