Patent ID: 6661291
Filing Date: 2003-12-09
Classification: H03J,H03L

Abstract:
A frequency synthesizer comprising in a phase-locked loop:a phase-frequency comparator (16) connected to a reference frequency source (20), at least a voltage-controlled oscillator (12) and a fractional frequency divider (14) suitable for producing a mean dividing ratio having an integral component and a fractional component, the frequency divider being connected between the voltage-controlled oscillator (12) and the phase-frequency comparator (16), characterized in that the voltage-controlled oscillator comprises a plurality of oscillator stages which have different center frequencies, in that the synthesizer further includes means for selecting (13, 50) an oscillator stage, and in that the center frequencies of the voltage-controlled oscillator stages conform to an arithmetical progression and a calibration means comprise a first and a second counter (64a, 64b), clocked by the voltage-controlled oscillator (12) associated to the frequency divider (14) and by the reference frequency source (20), respectively, a subtracter (68) connected to the counters for establishing a counting difference, and means (70, 72) for correcting a selection as a function of the counting difference.