Frequency synthesizer
AssigneeCanon Kabushiki Kaisha
InventorsSomei Kawasaki, Fujio Kawano
Life of this patent
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Abstract
The invention proposes a frequency synthesizer for generating an output signal having a frequency associated with that of a reference clock, in which a control oscillating circuit generates a clock signal group including a plurality of clock signals having a phase difference associated with the period of the output signal, and the oscillating frequency of the control oscillating circuit is controlled in accordance with the phase difference between a comparison clock generated by selectively using the plurality of clock signals, and the reference clock.
Claims16
A frequency synthesizer for generating an output signal having a frequency which is associated with a frequency of a reference clock, comprising:
- oscillating means for generating a clock signal group including a plurality of clock signals which have a phase difference associated with a period of the output signal;
- comparison clock generation means for selecting two clock signals corresponding to a target frequency of the output signal from the plurality of clock signals and for generating a comparison clock having a phase associated with phases of the two selected clock signals;
- phase difference detection means for detecting a phase difference between the reference clock and the comparison clock;
- and
- frequency control means for controlling an oscillating frequency of said oscillating means in accordance with an output of said phase difference detection means.
A frequency synthesizer for generating a output signal having a frequency which is associated with a frequency of a reference clock, comprising:
- oscillating means for generating a clock signal group including a plurality of first clock signals having phase differences obtained by equally dividing a period o the output signal into n phases;
- selection means for selecting two clock signals having neighboring phases from the plurality of clock signals;
- comparison clock generation means for outputting a signal having one of m phases obtained by substantially equally dividing the phase difference between the two selected signals into m phases, as the comparison clock;
- phase difference detection means for detecting a phase difference between the reference clock and the comparison clock;
- and
- frequency control means for controlling an oscillating frequency of said oscillating means in accordance with an output of said phase difference detection means.
An image forming apparatus comprising:
- oscillating means for generating a clock signal group including a plurality of clock signals which have a phase difference associated with a period of an output signal;
- comparison clock generation means for generating a comparison clock by selectively using the plurality of clock signals;
- phase difference detection means for detecting a phase difference between the reference clock and the comparison clock;
- frequency control means for controlling an oscillating frequency of said oscillating means in accordance with an output from said phase difference detection means;
- modulation means for modulating image data on the basis of an output from said frequency control means;
- image forming means for forming an image on the basis of the image data modulated by said modulation means;
- and
- comparison clock control means for controlling operation of said comparison clock generation means on the basis of a size of an image to be formed by said image forming means.
A frequency synthesizer for generating an output sign having a frequency which is associated with a frequency of a reference clock, comprising:
- oscillating means for generating a clock signal group including a plurality of clock signals having phase differences obtained by equally dividing a period of the output signal into n phases;
- comparison clock generation means for selecting two clock signals having neighboring phases from the plurality of clock signals and for generating a comparison clock on the basis of the two selected clock signals;
- phase difference detection means for detecting a phase difference between the reference clock and the comparison clock;
- and
- frequency control means for controlling an oscillating frequency of said oscillating means in accordance with an output of said phase difference detection means.
Dependencies are inferred from the claim text.