Design and Implementation on Dual-modulation Phase Lock Loop Synthesizer
Yongtai Chen · Modern Electronics Technique · 2007
Because of error transfer function′s high pass property in loop circuit,frequency offset(or phase offset) would diminish even disappear in FSK modulation system of PLL synthesizer which realized by modulating VCO.This paper proposes dual-modulation to solve this problem which is the way to modulate reference source and VCO of loop circuit at the same time.Under some circumstance,frequency offset of dual-modulation would not be influenced by loop circuit.And high stability of carrier frequency would be guaranteed.Through calculation,this paper gives the formula,the character of the circuit and the way how to meet the demand above.Dual-modulation can realize modulation with any signal from low frequency to DC.And it is proved effective through experiments.