Fast tuned phase locked loop frequency control system

Details Fast tuned phase locked loop frequency control system Fast tuned phase locked loop frequency control system

1982-12-20

1985-07-09

LaRoche, Eugene R.

Oscillators

Automatic frequency stabilization using a phase or frequency...

Plural a.f.s. for a single oscillator

331 14, 331 16, H03L 706

Patent

active

045285233

ABSTRACT:
An improved circuit for rapidly locking the phase of a reference signal e.sub.r of frequency f.sub.r with the phase of a signal e.sub.VCO in a phase locked loop which comprises a voltage controlled oscillator (VCO) for generating the signal e.sub.VCO of frequency f.sub.VCO, a divide-by-N circuit, for dividing f.sub.VCO by a variable N, a frequency/phase detector responsive to the phases of e.sub.VCO and e.sub.r to supply a control signal e.sub.c to the VCO, a loop filter circuit comprising a resistor and a capacitor for filtering e.sub.c, and logic for changing N to a new value N' in a time interval not less than T. Also provided is a circuit responsive to each change of N for coarse tuning the control signal supplied to the VCO and comprising a voltage generator responsive to each new value N' of N for generating a coarse tuned voltage having a magnitude which, when applied across the capacitor, will change the frequency f.sub.VCO /N to f.sub.VCO /N' to approximate f.sub.r. Gating logic responds to each change in N to disconnect the output of the frequency/phase detector and coincidentally to supply the coarse tuned voltage across the capacitor for a time interval .DELTA., where .DELTA.<<T, and then to reconnect the output of the frequency/phase detector.

REFERENCES:
patent: 3676794 (1972-07-01), Bidell et al.
patent: 4105948 (1978-08-01), Wolkstein

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