Oscillators – Automatic frequency stabilization using a phase or frequency... – Plural oscillators controlled
Patent
1986-01-31
1987-08-11
LaRoche, Eugene R.
Oscillators
Automatic frequency stabilization using a phase or frequency...
Plural oscillators controlled
331 15, 331 16, 331 25, H03L 706
Patent
active
046864881
ABSTRACT:
A frequency synthesizer of the fractional N type comprising a primary voltage controlled oscillator for producing an output signal which is afforded to a phase detector via a divider to provide a control signal for the primary voltage controlled oscillator in the presence of a phase difference between a reference signal from a reference source and the signal afforded thereto from the divider, the division ratio of which may be varied in a fractional N mode to vary the frequency of the output signal in frequency steps smaller than the frequency of the reference signal and wherein a ripple signal tending thereby to be produced and causing frequency modulation of the output signal is compensated by a phase modulator, arranged to couple the divider and the phase detector and to receive a drive signal in antiphase to the ripple signal, wherein the synthesizer further comprises a subsidiary phase lock loop arranged to provide an enhanced representation of the ripple signal in dependence upon the signal afforded to the phase detector from the phase modulator, and a digital to analogue converter arranged to provide the drive signal for the phase modulator in dependence upon the enhanced representation of the ripple signal.
REFERENCES:
patent: 3798550 (1974-03-01), Takaoka
patent: 4609881 (1986-09-01), Wells
LaRoche Eugene R.
Mis David
Oglo Michael F.
Plessey Overseas Limited
Renfro Julian C.
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