Phase-locked loop enabling the generation of a reference signal having a high spectral purity

Abstract

The invention relates to a phase-locked loop, comprising: an oscillator OSC intended to produce an output signal VIo, a frequency divider DIV intended to receive the output signal Vlo from the oscillator OSC, and a phase/frequency detector PD intended to compare the frequency FDIV of the output signal Vdiv of the divider DIV with the frequency of a comparison signal Vcomp, and to supply a tuning signal Vtun to the oscillator, which tuning signal defines the oscillation frequency of the oscillator, A phase-locked loop in accordance with the invention is provided with correction means PMOD intended to detect a parasitic phase modulation applied to the output signal VIo of the oscillator OSC, and to apply a phase modulation, which is similar to said parasitic phase modulation, to the comparison signal Vcomp. The invention enables a fractional-N frequency divider to be used and hence the noise generated by the loop to be limited, without affecting the spectral purity of the output signal Vlo of the oscillator OSC. Application: Tuners for receivers of television and radiotelephone signals.

Dependencies are inferred from the claim text.