Dynamic magnetic information storage or retrieval – General processing of a digital signal – Data clocking
Reexamination Certificate
1999-03-11
2001-02-20
Kim, W. Chris (Department: 2753)
Dynamic magnetic information storage or retrieval
General processing of a digital signal
Data clocking
C360S053000
Reexamination Certificate
active
06191905
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetic disc apparatus and in particular, to a magnetic disc apparatus for producing a pulse of a reproduction signal within a window.
2. Description of the Related Art
In a magnetic disc apparatus, a peak shift phenomenon can be seen. That is, a reproduction signal has a peak not stable and shifted. The range allowed for this peak shift is called a window margin, indicating the character of data read/write performance. In order to reduce the error rate indicating a bit mismatch between a recording signal and a reproduction signal, the window margin is adjusted in accordance with the performance of a magnetic disc medium. There have been suggested various methods to adjust this window margin according to a magnetic disc position or for respective heads.
For example, Japanese Patent Publication (unexamined) A3-95773 [1] discloses a method in which a multi-phase window is generated so as to select a window having an optimal phase difference with respect to a data signal.
Moreover, Japanese Patent Publication (unexamined) A9-180373 [2] filed by the same applicant as the present invention discloses a method of setting this window margin as follows. That is, a window position is shifted firstly in the plus direction and the minus direction, so as to determine error rates at the shifted positions. Next, a window margin is set according to the value of the error rate.
However, in the aforementioned conventional examples, the window position is modified at a constant interval and measurement is performed only once at each of the measurement points. Accordingly, when the same optimization is performed, there is a case that an optimal value is obtained at a position different from the previous optimization.
Especially, the inventor of the present invention has found in Document [2], that the window margin is not always maximum at the position where the parameter is optimal.
The inventor analyzed this problem and concluded that this problem is caused by the fact that each of the error rates for calculating the window margin (WDM) is measured only once at each window shift (WSF) point where the error rate easily fluctuates and that the optimization program including the window margin measurement is a procedure for varying one point in each parameter with an identical interval (step).
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a magnetic disc apparatus capable of reducing the error rate and obtain a preferable reproduction signal.
Another object of the present invention is to provide a magnetic disc apparatus capable of performing a window shift margin measurement with a higher accuracy and at a higher speed than in the conventional magnetic disc apparatus.
The magnetic disc apparatus according to the present invention comprises: a magnetic disc for recording a data; a reproduction head for reproducing a data recorded on the magnetic disc; and a signal processor for shaping a reproduction signal reproduced by the reproduction head and generating a pulse from the reproduction signal by using an optimized window.
The signal processor includes: (i) means for setting measurement points at an interval which is smaller in the vicinity of an initial position of a window than in the vicinity of the maximum modification position; (ii) means for shifting the window from the initial position up to the maximum modification position; (iii) means for reproducing a check data recorded on the magnetic disc so as to measure an error rate each time the window position is shifted according to the aforementioned interval; and (iv) means for using the error rate measurement results to obtain an optimal position of the window.
Thus, the region associated with the window margin position is checked accurately to obtain a high accuracy, while the region not affecting the optimization of the window margin position is checked roughly to reduce the time required for the check.
REFERENCES:
patent: 5760982 (1998-06-01), Stein
patent: 5995305 (1999-11-01), McNeil et al.
Kim W. Chris
NEC Corporation
Young & Thompson
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