Digital phase modulation of frequency synthesizer using modulated fractional division

摘要

A phase-locked loop frequency synthesizer system is provided using fractional frequency division and a fractional control number for phase modulating an output of the frequency synthesizer using an incoming information signal. The apparatus includes a delta-sigma converter which adjusts a divisor of the frequency divider by operating upon a magnitude modulated fractional frequency control number. The system further includes a differentiator which provides the magnitude modulated input stream to the delta-sigma modulator by modulating the fractional control number with detected differences in the incoming information signal.