Dynamic magnetic information storage or retrieval – General processing of a digital signal – Head amplifier circuit
Reexamination Certificate
2000-01-28
2003-03-11
Holder, Regina N. (Department: 2651)
Dynamic magnetic information storage or retrieval
General processing of a digital signal
Head amplifier circuit
C360S065000, C360S040000
Reexamination Certificate
active
06532122
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a data storage apparatus for magnetic recording and regeneration, such as a hard disk drive, a magnetic tape apparatus and a magneto-optic recording apparatus, as well as a magnetic recording method and a recording method, and more particularly to a data storage apparatus ensuring an improved reliability of regenerative data by extension of magnetic transition intervals upon the recording on a medium.
2. Description of the Related Arts
A data magnetic recording system of the conventional hard disk drive has a configuration as depicted in
FIG. 1
for example. The data magnetic recording system is constituted of a write unit
210
and a read unit
212
. The write unit
210
comprises an encoder
216
, a precoder
218
and a write driver
222
, and serves to perform a magnetic recording of data on a magnetic disk by means of a head/medium
224
. The read unit
212
comprises a preamplifier
226
, a variable gain amplifier
228
, a lowpass filter (LPF)
230
, a sampler (analog-to-digital converter)
232
, an equalizer
234
, a Viterbi detector (maximum likelihood detector)
236
, a decoder
238
, a gain calculator
240
, a phase calculator
242
, a VFO
244
and a tap gain calculator
246
. Data fed into the write unit
210
is subjected to any coding, typically RLL (Run Length Limited) coding, after which they pass through the precoder
218
, with the write driver
222
feeding a write current of a rectangular waveform as indicated in
FIG. 2A
into the recording head to form a magnetic transition on a record medium in compliance with the codes. The direction of this write current determines the direction of fluxes on the medium as indicated in
FIG. 2B
, and the reversal of the write current corresponds to the magnetic transition. In the event of regenerating such fluxes on the medium by the read head, the head output signal may typically result in a signal having its peaks at the magnetic transition positions as indicated by broken lines in FIG.
2
C. However, ISI (Inter-Symbol Interference) arising from the neighboring magnetic transitions gives rise to a signal as indicated by the solid line. The resultant head output signal is fed, through the preamplifier
226
, the variable gain amplifier
228
, the lowpass filter (LPF)
230
and the sampler
232
, into the equalizer
234
which equalizes the signal into a desired waveform to thereby provide a waveform of the equalizer output signal as indicated in FIG.
2
D. This equalizer output signal waveform corresponds to PR4 (partial response class 4) and is equalized so as to provide noise-free sampling values (expected values) equal to +1, 0 and −1 as indicated by circles. The sampling values pass through the Viterbi detector
236
for demodulating the recorded codes, with the resultant codes being finally decoded into original data in the decoder
238
.
However, such a data magnetic recording system of the conventional hard disk drive entails problems which follow.
FIGS. 3A
to
3
C illustrate the problems involved in the prior art.
FIGS. 3A
,
3
B and
3
C show the write current, the state of fluxes and the head output signal, respectively. First of all, with the increasing recording density there appear media noise or nonlinear phenomena, making it difficult to correctly demodulate into original data in spite of the equalization into a desired waveform as indicated in
FIG. 2D
by means of the equalizer
234
. In the event of recording at the minimum magnetic transition intervals (code bit interval in case of RLL code d=0) in particular, there may remarkably occur phenomena such as nonlinear transition shift known as NLTS or partial erasures known as PE. For a countermeasure against the nonlinear transition shift NLTS, a correction is currently made by means of a write pre-compensation method called WPC. In general, the nonlinear transition shift NLTS is a phenomenon in which, in case of magnetic transition consecutive on the medium, the posterior magnetic transition position is forward shifted as indicated by an arrow
250
of FIG.
3
B. Thus, the write pre-compensation WPC serves to cause the record current reversal position to shift backward to the solid line position as indicated by an arrow
252
so as to ensure the formation at the original magnetic transition position. Such a write pre-compensation WPC includes one capable of varying the amount of write compensation in response to the array of the magnetic transitions without being limited to the case of minimum magnetic transition intervals, although the similarity lies in that the posterior record current reversal position is shifted backward for the formation at the original magnetic transition position. The actual state of fluxes induced by such a write current may result in zigzagged magnetic transition positions as indicated in
FIG. 3B
, which has been considered as a major cause of the media noise. The partial erasure PE is a nonlinear amplitude reduction phenomenon which may occur in case the zigzagged magnetic transitions are enlarged and rightward fluxes are short-circuited at a part
154
so that no magnetic transition is formed. As a countermeasure against this partial flux PE it is similarly proposed to shift the write current reversal positions to extend the magnetic transition interval, thereby compensating the amplitude. It is therefore possible to effect a correction for the average value of the nonlinear transition shift NLTS or nonlinear distortions, by use of the method for shifting the magnetic transition positions.
However, those nonlinear distortions such as the nonlinear transition shift NLTS or the partial erasure PE are intrinsically stochastic phenomena, and it is envisaged that they are observed to be included in the media noise. Although this media noise increase with the increased recording density, no other measures than using the regenerative method having a larger S/N gain were found against the once-occurred medium noise dispersion. Furthermore, one of recent problems becoming more serious is a thermal relaxation phenomenon in which the recorded signals are degraded as a result of variations with time due to heat, whereupon it has been desired to record extended magnetic transition intervals. Thus, 1-7RLL code and 2-7RLL code free from any magnetic transition consecutive have also been given a consideration, although they have a poor code rate and involve characteristic problems or a problem that the clock frequency may inconveniently increase due to the wider bands.
SUMMARY OF THE INVENTION
According to the present invention there are provided a data storage apparatus, a magnetic recording method and a storage method capable of suppressing stochastic media noise of nonlinear phenomena such as nonlinear transition shift NLTS or a partial erasure PE and capable of improving the reliability of the regenerative data.
First, the present invention provides a data storage apparatus for magnetic recording and regeneration on a medium, the data storage apparatus comprising a write unit which, only in case of occurrence of a specific code sequence, records a magnetic transition interval on the medium with an extension relative to its original magnetic transition interval; and a read unit which, in a maximum likelihood detection after equalization of read signals of the medium, adds to an expected value of the maximum likelihood detection an amplitude error arising from extension record of the magnetic transition interval relative to the original magnetic transition interval. Thus, by extending the magnetic transition interval of a specific code sequence, the present invention is able to suppress the media noise, the stochastic amount of dispersion of the non-linear phenomena such as the nonlinear transition shift NLTS or the partial erasure PE as small as possible, and is able to provide an improved reliability of the regenerative data. Also, the positive extension of the magnetic transition intervals contributes to a solution t
Sugawara Takao
Tomimoto Shin
Fujitsu Limited
Greer Burns & Crain Ltd.
Holder Regina N.
Kapadia Varsha A.
LandOfFree
Data storage apparatus and magnetic recording method does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Data storage apparatus and magnetic recording method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Data storage apparatus and magnetic recording method will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3049185