Patent ID: 6229399
Filing Date: 2001-05-08
Classification: H03L

Abstract:
A PLL frequency synthesizer comprising:reference signal generation means for generating a reference signal of which frequency is controlled in accordance with a reference frequency control signal;phase comparing means for phase-comparing a frequency-divided signal with said frequency reference signal to output a phase difference signal;low-pass filter means for low-pass-filtering said phase difference signal with one of a plurality of cut-off frequencies selected in response to a filter control signal;voltage controlled oscillation means for generating and outputting an oscillation signal in a plurality of frequency bands in accordance with a band selection signal and an output of said low-pass filter means;frequency dividing means for frequency-dividing said oscillation signal and supplying said frequency-divided signal to said phase comparing means; andcontrol means for generating said reference frequency control signal and said filter control signal in accordance with a frequency command signal, wherein said voltage-controlled oscillation means generates and outputs said oscillation signal at a plurality of frequency bands, said band selection signal being determined from a predetermined combination of said reference frequency control signal and said filter control signal.