Phase-locked loop frequency tracking device including a direct digital synthesizer
First Claim
1. A phase-locked loop comprising:
- a phase detector for comparing the phase of an input signal having a time varying frequency with a return signal and for producing a DC magnitude signal proportional to the comparison;
a voltage controlled oscillator in communication with the phase detector for producing an AC signal representative of the DC magnitude signal from the phase detector; and
a signal generator for receiving the AC representative signal as a clocking frequency and producing the phase-locked loop output signal representative of the input signal, said output signal also acting as the return signal to the phase detector.
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Accused Products
Abstract
Disclosed is a single phase-locked loop (50, 350) providing tuning over a very large bandwidth for use in wide band carrier tracking and clock recovery systems. In a first embodiment, a DC signal is formed representative of a phase difference between an input signal changing with time and a return signal. The DC signal is applied to a narrow band voltage controlled oscillator (68) which converts the DC signal back to an AC signal. The AC signal is level shifted to form a clocking pulse for an accumulator (80) of a direct digital synthesizer (72). A digital command word is also applied to tyhe accumulator (80), such that the digital command word represents a coarse tuning of the input frequency. The clocking pulse from the narrow band VCO (68) supplies a fine tuning of the input frequency.
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Citations
20 Claims
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1. A phase-locked loop comprising:
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a phase detector for comparing the phase of an input signal having a time varying frequency with a return signal and for producing a DC magnitude signal proportional to the comparison; a voltage controlled oscillator in communication with the phase detector for producing an AC signal representative of the DC magnitude signal from the phase detector; and a signal generator for receiving the AC representative signal as a clocking frequency and producing the phase-locked loop output signal representative of the input signal, said output signal also acting as the return signal to the phase detector. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method of producing a loop output which tracks the frequency of an input carrier signal comprising the steps of:
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applying the input carrier signal to a phase detector; applying an output of the phase detector to a narrow band VCO; applying an output of the VCO to a direct digital synthesizer; and using an output of the direct digital synthesizer as the loop output and as the second input to the phase detector. - View Dependent Claims (10, 11, 12, 13, 14)
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15. A phase-locked loop comprising:
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a phase detector for generating a phase detection signal in response to an input signal which varies with time and a return signal; and a direct digital synthesizer for producing an output signal representative of the input signal in response to the phase detection signal, said output signal also acting as the return signal. - View Dependent Claims (16, 17, 18)
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19. A method of generating an output signal which tracks the frequency of an input signal comprising the steps of:
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comparing the phase of an input signal with the phase of a return signal; generating a magnitude signal representative of the comparison; applying the magnitude signal to an input of a VCO to generate an oscillating signal having a frequency indicative of the comparison; generating the input signal tracking output signal by using the oscillating signal as a frequency clock signal input to a signal generator; and employing the input signal tracking output signal as the return signal. - View Dependent Claims (20)
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Specification