Sample and hold type fractional-N frequency synthesizer

1. Field of the Invention A phase-locked loop (PLL) fractional-N type frequency synthesizer incorporates a sample-and-hold circuit. The synthesizer can reduce circuit size by eliminating a loop filter. Further, the synthesizer can incorporate fractional spur compensation circuitry to compensate char...

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Bibliographic Details
Main Authors Lee, Jeongwoo, Koo, Yido, Lee, Kang Yoon, Song, Eunseok, Huh, Hyungki, Park, Joonbae, Lee, Kyeongho
Format Patent
LanguageEnglish
Published 09.03.2004
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Summary:1. Field of the Invention A phase-locked loop (PLL) fractional-N type frequency synthesizer incorporates a sample-and-hold circuit. The synthesizer can reduce circuit size by eliminating a loop filter. Further, the synthesizer can incorporate fractional spur compensation circuitry to compensate charge pump ripple whenever a charge pump operates. The synthesizer or fractional-N type PLL can use a divider and at least two phase detectors coupled to a sample-and-hold circuit. A lock detecting circuit can initially determine a reference voltage for the sample-and-hold circuit. Also, fractional compensation is accomplished dynamically and in a manner that is robust to environmental changes while a control voltage is stably maintained for the voltage controlled oscillator.