| 摘要 |
PURPOSE:To attain PCM demodulation without jitter by setting the cut-off frequency of a loop filter inserted in the loop of a PLL circuit for generating read clock lower than the warp frequency of a recording disc at reproduction so as to eliminate jitter component due to the eccentricity of the disc. CONSTITUTION:Since the mechanical system such as an actuator drive device cannot sufficiently track the high frequency component of residual jitter even in a tangential servo system, jitter cannot completely by eliminated. Then in the digital information demodulation system 14, the cut-off frequency of the LPF 32 of a PLL circuit generating a read clock is set lower than the maximum frequency of the band of a tangential servo loop to cut the high frequency component of the residual jitter thereby eliminating the residual jitter component. More preferably, the cut-off frequency of the LPF 32 is set lower than the warp frequency of the disc (30-8Hz in LDD) so as to eliminate completely even the jitter due to the eccentricity of the disc. |
