Digital phase-locked loop frequency modulator
AssigneeGTE Sylvania Incorporated
InventorHerbert S. Madoff
Life of this patent
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Abstract
Frequency modulating apparatus employing a phase-locked loop. An analog signal is sampled periodically and each sample is converted to a digital signal by an analog-to-digital converter. A constant is added to the digital signal and the sum is employed as the divisor of a programmable divider connected in the phase-locked loop between the output of the voltage controlled oscillator and an input of a phase detector. The output of the voltage controlled oscillator is also divided by an output divider and then filtered to provide a sinusoidal output signal. The resulting output signal is at a center frequency which is frequency modulated by the analog signal.
Claims4
Frequency modulating apparatus including in combination
- means for producing a reference frequency signal;
- a voltage controlled oscillator;
- programmable dividing means coupled to the output of the voltage controlled oscillator for dividing the frequency of the output signal from the voltage controlled oscillator by a divisor;
- phase detector means having a first input coupled to said means for producing a reference frequency signal, a second input coupled to the output of said programmable dividing means, and an output coupled to the input of the voltage controlled oscillator to produce a phase-locked loop in which the frequency of the output signal from the voltage controlled oscillator is equal to the frequency of the reference frequency signal multiplied by said divisor;
- signal converting means for receiving an input signal and for converting the input signal to digital signals;
- storage means coupled to said signal converting means for holding a digital signal therefrom;
- and
- divisor means coupled to said storage means and to said programmable dividing means for applying to said programmable dividing means a divisor representing the digital signal held by said storage means, whereby the frequency of the output signal from the voltage controlled oscillator is modulated by the input signal being received.
Dependencies are inferred from the claim text.