Patent ID: 6670854
Filing Date: 2003-12-30
Classification: H03L,Y10S

Abstract:
A method of operating a fractional-N frequency synthesizer, comprising the steps of:preparing a sigma-delta noise shaper; setting integral and fractional parts of a frequency divide ratio-setting value for frequency-dividing an output signal; applying the fractional part of the frequency divide ratio-setting value to said sigma-delta noise shaper every phase comparison period; summing up an output from said sigma-delta noise shaper and the integral part of the frequency divide ratio-setting value to thereby create a sum; frequency-dividing the output signal, using this sum as a frequency divide ratio; producing a difference between the fractional part of said frequency divide ratio-setting value and the output from said sigma-delta noise shaper; accumulating said difference in an accumulator every phase comparison period; and producing a spurious-canceling value based on a value obtained from said accumulator.