Patent ID: 6188740
Filing Date: 2001-02-13
Classification: H03L

Abstract:
A fractional-N system frequency synthesizer comprising:a reference oscillator for generating a reference signal having a predetermined frequency;a modulo-m counter for counting said reference signal from said reference oscillator;a voltage controlled oscillator for generating an oscillation signal having a predetermined frequency;a switching signal generator coupled with said modulo-m counter for generating a switching signal comprising a plurality of selecting pulses with equi-intervality;a programmable counter, to which the output from said voltage controlled oscillator is supplied, for outputting an output signal of a predetermined frequency having a different dividing ratio in response to said switching signal from said switching signal generator; anda phase comparator for comparing said output signal from said program counter with said reference signal from said reference oscillator, in order to generate a phase error signal between said output signal from said program counter and said reference signal, the output of said phase comparator being supplied to said voltage controlled oscillator to control the oscillation frequency of said oscillation signal from said voltage controlled oscillator.