Oscillators – Automatic frequency stabilization using a phase or frequency... – Afc with logic elements
Patent
1979-05-10
1981-06-09
Grimm, Siegfried H.
Oscillators
Automatic frequency stabilization using a phase or frequency...
Afc with logic elements
331 4, 331 11, 331 25, H03L 712
Patent
active
042727294
ABSTRACT:
The automatic pretuning of a voltage controlled oscillator in a phase locked loop frequency synthesizer utilizes a successive approximation technique to rapidly bring the coarse tuning voltage of the oscillator to the desired pretuning value. A digital number stored in a digital register is converted to an analog voltage value and applied to the voltage controlled oscillator as the coarse tuning voltage. The frequency of the output signal from the oscillator is compared with a reference signal, and control logic responsive to the sense of the frequency difference between the reference signal and the oscillator output signal adjusts the value of the number stored in the digital register successively from the most significant bit to the least significant bit. A microprocessor can be used to adjust the value of the number stored in the register, as well as provide additional functions such as reverse successive approximation when the synthesizer is switched from one frequency to another frequency. The microprocessor can also be used to sweep the coarse tuning voltage of the oscillator until the output signal is within the capture range of the phase locked loop, and thereafter perform a successive approximation function to bring the coarse tuning voltage to the center of the capture range.
REFERENCES:
patent: 3401353 (1968-09-01), Hughes
patent: 3825855 (1974-07-01), Basset et al.
patent: 4103250 (1978-07-01), Jackson
patent: 4105948 (1978-08-01), Wolkstein
patent: 4107623 (1978-08-01), Graf et al.
Grimm Siegfried H.
Harris Corporation
Rogers, III L. Lawton
Westin Edward P.
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