Dynamic magnetic information storage or retrieval – General processing of a digital signal – Data in specific format
Reexamination Certificate
1998-11-05
2001-03-06
Kim, W. Chris (Department: 2651)
Dynamic magnetic information storage or retrieval
General processing of a digital signal
Data in specific format
Reexamination Certificate
active
06198585
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention generally relates to a digital signal recording apparatus, and particularly relates to an apparatus for recording a digital signal and an amble pattern signal on a magnetic recording medium. This invention also relates to a method of recording a digital signal on a recording medium.
2. Description of the Related Art
In some digital VTR's (video tape recorders), a digital information signal is recorded on a magnetic tape while an array of slant tracks is formed thereon. Each slant tracks is divided into areas assigned to main information pieces (for example, video information pieces, audio information pieces, subcode information pieces, and digital data pieces), and areas assigned to signals representing amble patterns such as a preamble pattern and a post-amble pattern. The main-information areas are separated by the amble-pattern areas.
The signals recorded on the amble-pattern areas are designed to decide the phase of a clock signal derived from reproduced data, to enable the absorption of errors in signal record positions during an editing process, and to compensate for an error in a track reproduction position due to a positional head attachment error.
In a typical digital VTR, a signal reproduced from a magnetic tape by magnetic heads is subjected to an equalization process by a waveform equalizer, and the equalization-resultant signal is converted into a binary digital signal (a bi-value digital signal). Then, a PLL (phase locked loop) circuit derives a clock signal from the binary digital signal. Accordingly, it is desirable that signals recorded on amble-pattern areas have such lengths as to stabilize the data derivation phase provided by the PLL circuit, and that the signals recorded on the amble-pattern areas provide such data inversion intervals as to easily enable the derivation of the clock signal.
In general, since a PLL circuit responds to data state inversions, an amble-pattern signal, which has many data state inversions during a given time interval, is effective in deriving a clock signal. For example, an amble-pattern signal which represents a bit sequence as “101010 . . . ” is the most effective in providing a locked state of the PLL circuit, and in optimizing the phase of the derived clock signal.
It is known to use partial responses in magnetic recording and reproducing apparatuses. During the reproduction of a digital signal from a magnetic recording medium, the digital signal is differentiated by a magnetic head so that the reproduced signal outputted from the magnetic head basically has a differentiation-resultant waveform. Since a reproducing device including the magnetic head has a narrow passband width, the actual waveform of the reproduced signal agrees with a rounded or smoothed differentiation-resultant waveform.
According to a partial-response detection system “PR(1)” based on integral detection, the center level of the waveform of the output signal from the magnetic head is used to decide whether a reproduced signal state corresponds to a logic state of “1” or a logic state of “0”. When a bit sequence represented by a recorded signal on a magnetic recording medium is denoted by “a
k
”, a detected or reproduced signal bit sequence “b
k
” provided in the partial-response detection system “PR(1)” is given as “b
k
=a
k
”. In this case, an amble pattern “101010 . . . ” is detected and reproduced as a bit sequence “101010 . . . ” which is the most convenient for a PLL circuit to derive a clock signal.
According to a partial-response detection system “PR(1, 0, −1)” better than the partial-response detection system “PR(1)”, a recorded signal bit sequence “a
k
” and a detected or reproduced signal bit sequence “b
k
” are related as follows.
b
k
=a
k
⊕a
k-2
where “⊕” denotes modulo 2 addition. In this case, an amble pattern “101010 . . . ” is detected and reproduced as a bit sequence “100000 . . . ” which is inconvenient for a PLL circuit to derive a clock signal.
SUMMARY OF THE INVENTION
It is an object of this invention to provide a digital signal recording apparatus which generates and records an amble-pattern signal convenient for both a partial-response detection system “PR(1)” and a partial-response detection system “PR(1, 0, −1)” to derive a clock signal.
It is another object of this invention to provide a digital signal recording apparatus which includes a simple circuit for generating an amble-pattern signal.
It is sill another object of this invention to provide an improved method of recording a digital signal on a recording medium.
A first aspect of this invention provides a digital signal recording apparatus comprising an amble generator for generating an amble signal representing a bit-sequence amble pattern, wherein the bit-sequence amble pattern can be detected and reproduced by a partial-response detection system “PR(1, 0, −1)” as a detected amble pattern having a period of state inversions which is shorter than a period of state inversions in a detected amble pattern corresponding to a recorded amble pattern of alternation of “1” and “0”; means for combining the amble signal generated by the amble generator and a first digital information signal into a second digital information signal on a time sharing basis; and means for recording the second digital information signal on a magnetic recording medium.
A second aspect of this invention is based on the first aspect thereof, and provides a digital signal recording apparatus wherein the bit-sequence amble pattern represented by the amble signal has repetition of six bits of “111000”.
A third aspect of this invention is based on the first aspect thereof, and provides a digital signal recording apparatus wherein the bit-sequence amble pattern represented by the amble signal has repetition of eight bits of “11110000”.
A fourth aspect of this invention provides a digital signal recording apparatus comprising means for generating a first digital signal; means for generating an amble signal representing a bit sequence having repetition of six bits of “111000”; means for combining the first digital signal and the amble signal into a second digital signal on a time sharing basis; and means for recording the second digital signal on a recording medium.
A fifth aspect of this invention provides a digital signal recording apparatus comprising means for generating a first digital signal; means for generating an amble signal representing a bit sequence having repetition of eight bits of “11110000”; means for combining the first digital signal and the amble signal into a second digital signal on a time sharing basis; and means for recording the second digital signal on a recording medium.
A sixth aspect of this invention provides a digital signal recording method comprising the steps of generating an amble signal representing a bit-sequence amble pattern, wherein the bit-sequence amble pattern can be detected and reproduced by a partial-response detection system “PR(1, 0, −1)” as a detected amble pattern having a period of state inversions which is shorter than a period of state inversions in a detected amble pattern corresponding to a recorded amble pattern of alternation of “1” and “0”; combining the generated amble signal and a first digital information signal into a second digital information signal on a time sharing basis; and recording the second digital information signal on a magnetic recording medium.
A seventh aspect of this invention is based on the sixth aspect thereof, and provides a digital signal recording method wherein the bit-sequence amble pattern represented by the amble signal has repetition of six bits of “111000”.
An eighth aspect of this invention is based on the sixth aspect thereof, and provides a digital signal recording method wherein the bit-sequence amble pattern represented by the amble signal has repetition of eight bits of “11110000”.
REFERENCES:
patent: 4242755 (1980-12-01), Gauzan
patent: 5512349 (1996-04-01), Chiba et al.
patent: 5583705 (1996
Higurashi Seiji
Ohishi Takeo
Zenno Yoichi
Connolly Bove Lodge & Hutz
Kim W. Chris
Victor Company of Japan Ltd.
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