Patent ID: 6703901
Filing Date: 2004-03-09
Classification: H03L

Abstract:
A frequency synthesizer comprising a phase-locked loop (10) and comprising:a frequency divider (14) having integral dividing ratios, connected between a voltage-controlled oscillator (12) and a phase/frequency comparator (16), a sigma-delta modulator (30) connected to the frequency divider (14) for switching the dividing ratio of the frequency divider between a series of at least two integral values, so as to obtain a resulting mean dividing ratio having a fractional component, the modulator having at least an input (32) suitable for receiving an adjusting instruction of the fractional component, and at least a frequency divider (100) having a fixed fractional dividing ratio, connected between the voltage-controlled oscillator (12) and the frequency divider having integral dividing ratios (14), and means for activating the divider (100) having a fractional dividing ratio when the fractional component (k) of the mean dividing ratio is contained in at least a given value range, and for modifying the adjusting instruction of the fractional component of the sigma-delta modulator.