| 摘要 |
PURPOSE: A jitter measuring circuit for an optical disc is provided to prevent the synchronization of a digital signal at a zero crossing point of an optical pickup wave signal and reduce the range of deviation, thereby reducing the deviation between analog signal and digital signal without using a high frequency clock cycle. CONSTITUTION: A jitter measuring circuit for an optical disc includes an A/D converter(401), a zero crossing detection part(405) for detecting a zero crossing point by detecting a position of polarity conversion from a digital signal output from the A/D converter, a counter part(407) for counting the number of clocks of an optical pickup wave signal and four times clocks from the zero crossing point to a system clock edge point, a zero crossing time operation part(403) for operating Tnj and Tpj from the zero crossing point information output from the zero crossing point detection part, and a jitter calculation part(409) for outputting flag information for representing the system clock number of the optical pickup wave, deviation information and the polarity of the deviation information. Tnj represents a cycle from the zero crossing point to a first 4-times clock and Tpj represents a cycle from a final 4-times clock to the zero crossing point.
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