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Transmission system for digital signals, and transmitter and receiver therefor

  • US 5,881,107 A
  • Filed: 03/11/1997
  • Issued: 03/09/1999
  • Est. Priority Date: 03/11/1996
  • Status: Expired due to Term
First Claim
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1. A transmission system for a digital signal (sr) which, encoded in symbols (Si), is transmitted from a transmitter (T) to a receiver (R) by quadrature modulation, wherein:

  • said transmitter comprises means for delaying one of the two quadrature signal components (ki, kq) before the quadrature modulation by a given time interval (td) substantially equal to one quarter of a symbol period Tsymb or by one quarter of the period of the quadrature carrier (tr) in the transmitter (T); and

    ,said receiver (R) comprises;

    clock recovery means;

    an analog-to-digital converter coupled to said clock recovery means;

    said analog-to-digital converter for forming a sampled signal (sd) from a received signal (s(t)), and utilizing a sampling frequency fs being substantially equal to four times the symbol frequency fsymb ;

    a demultiplexer coupled to said clock recovery means;

    said demultiplexor for separating the sampled signal (sd) into an in-phase component (ki) for an I data path (I) and a quadrature component (kq) for a Q data path (Q) which are each filtered by means of a respective pulse-shaping filter (FI2, FQ2) with an IIR filter structure; and

    a quadrature mixer coupled to said clock recovery means.

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