Noise reduction method and apparatus for phase-locked loops

Details Noise reduction method and apparatus for phase-locked loops Noise reduction method and apparatus for phase-locked loops

1991-09-09

1993-06-01

Mis, David

Oscillators

Automatic frequency stabilization using a phase or frequency...

Plural a.f.s. for a single oscillator

331 16, 331 25, 455260, H03L 7087, H03L 718

Patent

active

052163873

ABSTRACT:
Method and apparatus for improving the signal-to-noise ratio of a divide-by-N phase-locked loop includes a variable divider circuit to provide a plurality of feedback signals of substantially equal phase. Each of the plurality of feedback signals includes a signal component and a noise component wherein the signal components of the plurality of feedback signals have substantially equal phase and wherein the noise components of the plurality of feedback signals are not substantially correlated. A respective plurality of control circuits is provided to combine the plurality of feedback signals with a reference signal to provide a plurality of control signals wherein each control signal is a substantially direct current voltage the magnitude of which is proportional to the phase difference between the reference signal and the feedback signal which comprised its origin. The plurality of control signals are added to provide a composite control signal so that the signal components of the plurality of control signals add by linear superposition and so that the noise components of the plurality of control signals add by the square root of the sum of their squares, thereby substantially improving the signal-to-noise ratio of the phase-locked loop output.

REFERENCES:
patent: 3571743 (1968-10-01), Menkes
patent: 4888564 (1989-12-01), Ishigaki

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