| 摘要 |
A demodulation circuit accurately demodulates a wobble signal of an optical disk without being affected by a phase shift induced by crosstalk. An A-D converter subjects wobble signal reproduced from an optical disk to A-D conversion and feeds a result of conversion to a zero-crossing detection circuit. The zero-crossing detection circuit detects zero-crossing points of the wobble signal. A sinusoidal wave generation circuit generates a sinusoidal wave by means of sequentially connecting sinusoidal wave elements whose periods are each equal to a time interval between zero-crossing points. A multiplier multiplies an original wobble signal by a sinusoidal wave signal. A slicer detects an HMW-modulated portion of the wobble signal, and another slicer detects an MSK-modulated portion of the wobble signal.
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