Automatic phase and frequency control system
AssigneeZenith Radio Corporation
InventorRichard W. Citta
Life of this patent
Estimating the term…
Abstract
An automatic phase and frequency control system includes a pair of multipliers coupled to a source of input signal. A voltage controlled oscillator is also coupled to each of the multipliers. Means are provided to phase shift the oscillator signal at one multiplier such that quadrature beat signals are produced. The output of one of the multipliers is coupled directly to a third multiplier while the output of the other is coupled to a low pass filter. The filtered signal is amplitude limited and applied to the third multiplier. A second low pass filter couples the output of the third multiplier to the frequency control input of the voltage controlled oscillator.
Claims8
An automatic phase and frequency control system for producing phase and frequency synchronism between a locally generated signal and an input signal comprising:
- oscillator means producing an oscillatory signal having a frequency responsive to a control signal;
- generating means producing first and second beat signals between said input signals and said oscillatory signal, said beat signals having a substantially quadrature relationship;
- translating means converting said first beat signal to a constant amplitude signal having a phase relative to said second beat signal which varies in a predetermined relationship to said beat signal frequency, said translating means being capable of coupling a D.C. signal;
- first multiplying means multiplying said second beat signal and the output signal of said translating means to develop a control signal, said second beat signal being applied to said multiplying means such that the relative amplitude of said output signal of said translating means and said second beat signal remain substantially constant and the relative phase therebetween varies as a function of beat signal frequency;
- and
- first filter means coupling said control signal to said oscillator means.
An automatic phase and frequency control system for maintaining phase and frequency synchronism between a locally generated signal and an input signal:
- a voltage controlled oscillator producing an oscillatory signal having a frequency determined by an applied control signal;
- a first and a second multiplier each producing an output signal equal to the product of two input signals;
- means coupling the output signal of said voltage controlled oscillator and said input signal to the respective inputs of said first and second multipliers such that the output signals of said first and second multipliers are in quadrature;
- a first low pass filter, coupled to the output of said second multiplier having a predetermined phase delay characteristic producing a phase shift which varies as a function of signal frequency;
- a limiter, coupled to said first low pass filter, symmetrically limiting the amplitude of the output signal of said first low pass filter;
- a third multiplier, responsive to the output signals of said limiter and said first multiplier, producing an output signal equal to the product thereof, the output signal of said first multiplier being applied to said third multiplier such that the relative amplitudes of said output signals of said limiter and said first multiplier remain substantially constant and the relative phase therebetween varies as a function of beat signal frequency;
- and
- a second low pass filter coupling the output signal of said third multiplier to the control signal input of said voltage controlled oscillator.
Dependencies are inferred from the claim text.