Oscillators – Automatic frequency stabilization using a phase or frequency... – With intermittent comparison controls
Patent
1996-02-29
1997-12-09
Mis, David
Oscillators
Automatic frequency stabilization using a phase or frequency...
With intermittent comparison controls
331 17, 331 18, 331 34, 327156, H03L 708
Patent
active
056964684
ABSTRACT:
The clock multiplying phase locked loop includes components for selectively setting a center frequency of a voltage controlled oscillator (VCO) to bias the VCO for operation within a selected range of input frequencies. To this end, the VCO is configured to output a signal at a selected center frequency based upon a tuning current provided to the VCO. Initially, a voltage input of the VCO is set to a reference voltage and a feedback signal is generated. The feedback signal, perhaps divided by N, is input to a phase-frequency detector. The phase-frequency detector also receives a reference frequency signal having a frequency at the selected center frequency. The detector outputs an UP or DOWN signal indicating whether the feedback signal is greater or less than the reference frequency signal. A center frequency adjustment unit receives the UP or DOWN signals from the detector and adjusts the tuning current to modify the center frequency of the VCO to reduce any difference between the feedback frequency and the reference frequency received by the phase-frequency detector. The VCO, the detector and the adjustment unit, as well as other components, operate in a loop causing the center frequency of the VCO to be iteratively adjusted until the center frequency approximates the selected center frequency to a selected degree of resolution. At that point, the voltage reference signal is disconnected from the voltage input of the VCO and the frequency reference signal is disconnected from the input of the phase-frequency detector, thus allowing the clock multiplier to operate as a phase locked loop (PLL). The tuning current, however, continues to be applied to the VCO to maintain the center frequency of the VCO at the selected center frequency such that further operation of the VCO is biased to that center frequency. Method and apparatus embodiments of the invention are disclosed.
REFERENCES:
patent: 5359298 (1994-10-01), Abe
patent: 5382922 (1995-01-01), Gersbach et al.
patent: 5410592 (1995-04-01), Yoshida
patent: 5414390 (1995-05-01), Kovacs et al.
Edmonston Brian S.
Miller Russell B.
Mis David
Qualcomm Incorporated
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