| 摘要 |
PURPOSE:To detect an accurate position signal with a simple circuit constitution by disposing respective fine and coarse servo patterns suitably, A/D-converting directly a signal after peak-holding, and storing the signal in a memory. CONSTITUTION:A servo sector 40 consists of an erasing part 42, and AGC part 43, and a position part 44. As for a servo pattern in the part 44, servo patterns P, Q, R for coarse positioning between two-phase di-bit patterns A-D and a pattern Z for zone detection are suitably disposed. Signals on a disk 61 reproduced by magnetic heads 63a, 63b are supplied to a sample pulse generator 69 through pre-amplifiers 64a, 64b, an analog switch 65, an AGC amplifier 66, a binarization circuit 70, and an erase detection circuit 67, and sample by using the sample gate of the generator 69. The signals A-D are sequentially supplied to peak holding circuits 74, 75, and the holding output of them 74, 75 are A/D-converted 84, and stored in the memory of a CPU 79.
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