| 摘要 |
PROBLEM TO BE SOLVED: To improve the operation stability of the PLL circuit of a reproduction device that reproduces reproduction data in a high-density recording disk and, on the other hand, to generate a normal decoded signal from a maximum likelihood decoding circuit by responding to a shortest period read signal of the high-density recording disk.SOLUTION: An A/D converter 14 converts an RF signal of a disk into a digital signal. A reproduction signal including a shortest period signal with the length of the smallest mark and a long mark signal with the length of a long mark is supplied from the disk to a first offset reduction circuit 15. The circuit 15 does not respond to the shortest period signal and reduces the first DC offset of a reproduction signal of a long mark. A PLL circuit 16 responds to an A/D conversion digital signal from the circuit 15 and generates synchronous timing. A second offset reduction circuit 17 does not respond to a reproduction signal of a long mark and reduces second DC offset of the shortest period signal. A maximum likelihood decoding circuit 18 carries out maximum likelihood detection of a reproduction signal in which the first DC offset and the second DC offset are reduced in the circuits 15 and 17. |
