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Apparatus for reducing jitter of a spectrum spread clock signal and method therefor

  • US 5,651,035 A
  • Filed: 04/28/1995
  • Issued: 07/22/1997
  • Est. Priority Date: 04/28/1995
  • Status: Expired due to Fees
First Claim
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1. Apparatus for generating spectrum spread clock pulses, comprising:

  • a reference clock pulse generator that generates pulses at a reference clock frequency;

    means for generating a digital signal representation of an input angle;

    an accumulator connected to said reference clock and said generating means, said accumulator storing a digital signal representation of an accumulated angle in accordance with an input relationship which is given as;

    ##EQU2## where P is said accumulated angle;

    M is said input angle;

    K=2n ;

    K is the state size of said accumulator; and

    n is the number of binary bits stored by said accumulator;

    a phase locked loop arranged to includes a loop filter and a frequency divider, said phase locked loop having an input that is driven by the most significant bit (MSB) of the output of said accumulator; and

    means for removing a compensating charge from said loop filter during an overshoot interval when the output of said frequency divider differs from said MSB, wherein said overshoot interval is in accordance with a relationship which is given as;

    
    
    space="preserve" listing-type="equation">Δ

    T=[GT.sub.c ]/Mwhere Δ

    T is the overshoot interval;

    G=P-K/2 when the MSB changes from logic "0" to logic "1";

    Tc is the period of the pulses generated by said reference clock; and

    M is said input angle.

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