JPH07161010A - Magnetic recording method and magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To improve reproduced image quality by inverting the polarities of recording currents across a neutral level period for decreasing the recording currents without inverting the polarities. CONSTITUTION:The recording signals inputted from a recording signal input terminal 1 are shaped in waveforms by a recording signal control circuit 2 and are then recorded on a magnetic tape 5 by a recording amplifier 3 and a magnetic head 4 at the time of recording. The signals recorded on this magnetic tape 5 are read out by a reproducing head 6, are amplified by a reproducing amplifier 7, and are outputted from a reproduced signal output terminal 100 at the time of reproducing. The current off Period tau is provided just before the inversion of the polarity of the recording current iR by the operation of the recording signal control circuit 2 and the recording currents are not passed to the recording head 4 or the recording is executed by decreasing the current value to the extent that the magnetic tape 5 is not magnetized in this period in the case of recording of the NRZ digital signals of the pit interval T. The reproducing level of a short wavelength region with respect to the conventional square waveform recording is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording method for recording a digital signal on a magnetic recording medium and a magnetic recording / reproducing apparatus for recording or reproducing a digital signal on a magnetic recording medium, and more particularly to high density short wavelength recording. The present invention relates to a magnetic recording method and a magnetic recording / reproducing apparatus suitable for performing the above.

[0002]

2. Description of the Related Art In recent years, magnetic recording / reproducing devices are VTR, D
High-density recording is progressing, including AT (Digital Audio Tape Recorder), but in the home-use digital VTR that will be developed in the future, the track will be further narrowed.
And short wavelength recording is required. However, when the recording wavelength is shortened, there is a problem that the signal S / N ratio is deteriorated and a peak shift peculiar to magnetic recording occurs.

In order to solve this problem, a method of equalizing a waveform with a small peak shift at the time of reproduction, or a rising and falling edge of a pulse waveform to be recorded, as described in, for example, Japanese Patent Laid-Open No. 58-218014. A recording equalization method such as emphasizing is generally used.

[0004]

As described above, in high density recording, it is difficult to secure the signal S / N, and the S / N margin for the system is very small.

It is an object of the present invention to provide a magnetic recording method and a magnetic recording / reproducing apparatus capable of solving such a problem and improving the S / N ratio of signals in the system.

[0006]

In order to achieve the above-mentioned object, a magnetic recording method and a magnetic recording / reproducing apparatus according to the present invention have a magnetic recording medium having an easy axis of magnetization in an oblique direction or a perpendicular direction, and this magnetic recording medium. Record binary data on top /
A magnetic head for reproduction and a recording signal control circuit for reducing the recording current value for a certain period (τ) during data recording are provided, and the recording current of the recording current is reduced with a neutral level period τ for reducing the recording current without reversing the polarity. The polarity is reversed and this signal is supplied to the magnetic head for recording.

[0007]

The recording signal control circuit operates so as to provide the current-off period τ just before the polarity of the recording current is reversed with respect to the binary data to be recorded. During this period, the recording current is not passed through the recording head. Alternatively, recording is performed by reducing the current value so that the magnetic tape is not magnetized. Furthermore, if a magnetic recording medium having a magnetization easy axis in an oblique direction is used,
Due to the effect of the oblique magnetic field distribution of the recording head and the recording current off period τ, the residual magnetization intensity increases and the reproduction output signal level increases.

[0008]

Embodiments of a magnetic recording method and a magnetic recording / reproducing apparatus according to the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a main configuration of a magnetic recording / reproducing apparatus according to a first embodiment of the present invention. In FIG. 1, 1 is a recording signal input terminal, 2 is a recording signal control circuit, 3 is a recording amplifier, 4 is a recording head, 5 is a magnetic tape, 6 is a reproducing head, 7 is a reproducing amplifier, and 100 is a reproducing signal output terminal. is there.

First, at the time of recording, the recording signal inputted from the recording signal input terminal 1 is waveform-shaped by the recording signal control circuit 2 and then recorded on the magnetic tape 5 by the recording amplifier 3 and the recording head 4. During reproduction, the signal recorded on the magnetic tape 5 is read by the reproduction head 6, amplified by the reproduction amplifier 7, and then output from the reproduction signal output terminal 100.

FIG. 2 is a diagram showing recording current waveforms according to this embodiment and the prior art.

When an NRZ digital signal having a bit interval T shown in FIG. 2A is recorded as an input recording signal, the same as the input signal as shown in FIG. 2B in the prior art. It records with the square wave of. _Regarding the polarity and current value of the recording current i _R , for example, “1” of the recording signal is + i and “0” is −i.

On the other hand, in the present embodiment, the current off period τ is provided immediately before the polarity of the recording current i _R is reversed by the operation of the recording signal control circuit 2 as shown in FIG. Do not apply the recording current to the recording head 4 during the period?
Alternatively, the recording is performed by reducing the current value so that the magnetic tape 5 is not magnetized.

The current ME is used as the magnetic tape 5.
(Metal Evaporated) tape, which is a magnetic recording medium having an easy axis of magnetization in the oblique direction or a magnetic recording medium having an easy axis of magnetization in the perpendicular direction, is used. The playback level can be improved.

The reason why the reproduction level increases when the recording method of this embodiment (the present invention) is used will be described below.

FIG. 3 shows the relationship between the polarity and strength of the magnetic field acting on the magnetic recording medium by the ring-shaped magnetic head. Figure 3 shows longitudinal recording, vertical recording, and diagonal recording.
(A), FIG. 3 (b), and FIG. 3 (c).
That is, in longitudinal recording, as shown in FIG. 3A, the polarities of the magnetic field are the same in the vicinity of the leading magnetic pole L of the magnetic head and in the vicinity of the trailing magnetic pole T, and the magnetic field strength is ideally ideal. It is symmetrical to the gap centerline. On the other hand, in perpendicular recording, as shown in FIG. 3B, the polarities of the magnetic field are reversed in the vicinity of the leading-side magnetic pole L and the vicinity of the trailing-side magnetic pole T, and the magnetic field strength is ideally the gap. One of them is symmetrical with respect to the center line. On the other hand, in oblique recording, as shown in FIG. 3C, the polarities of the magnetic field are reversed in the vicinity of the leading-side magnetic pole L and in the vicinity of the trailing-side magnetic pole T, and the magnetic field strength is the center of the gap. The line becomes asymmetric.

The process of magnetizing a magnetic recording medium having an axis of easy magnetization in the oblique direction will be described below.

FIG. 4 shows a state immediately before the polarity of the recorded binary data is inverted (for example, immediately before it is inverted from "1" to "0").

Below the magnetic pole of the ring head, the recording current + i
The asymmetric recording magnetic field is formed by This recording magnetic field is a model of (c) of FIG. The magnetic recording medium has an easy axis of magnetization in an oblique direction that is oblique to the surface direction thereof, and is greatly magnetized to the positive electrode under the leading side magnetic pole L, and is magnetized to the negative electrode only under the trailing side magnetic pole T to the negative electrode. To be done. Therefore, although the magnetic recording medium is magnetized to the positive electrode as a whole, the strength of the magnetization decreases when it passes under the trailing magnetic pole T.

FIG. 5 shows the state of magnetization when the current off period τ is entered. Since the current value of the recording current is set to 0 in this period, the recording magnetic field is not formed under the magnetic pole of the ring head, and the magnetized state of the magnetic recording medium maintains the previous state.

FIG. 6 shows a state immediately after the end of the current off period τ.

Since the polarity of the recording current is reversed, an asymmetric recording magnetic field having a polarity opposite to that of FIG. 4 is formed under the magnetic pole of the ring head. Under the magnetic pole L on the leading side, the magnetic recording medium is largely magnetized to the negative pole, and under the magnetic pole T on the trailing side, only the surface is magnetized to the positive pole. However, because of the current-off period τ, the magnetized positive electrode in the state of FIG. 4 moves relatively while being left unreduced, so that the magnetization below the trailing side magnetic pole T is reduced. It will be strengthened. In the vicinity thereof, there is a region where the strength of magnetization has not decreased.

FIG. 7 shows a state slightly after the end of the current off period τ.

The width W at which the magnetization intensity does not decrease is present in the portion where the magnetization polarity is reversed where "1" of the recorded binary data is recorded.
A region of _T1 is formed, and a region of width W _T2 with enhanced magnetization is formed. It is estimated that the wider the widths W _T1 and W _{T2 of} these regions, the higher the signal output level.

The value of the current off period τ required in these operations is expressed by a function of the recording head gap length _gl and the tape head relative velocity v.

FIG. 8 shows a state in which the polarity of the recording current is immediately inverted without the current off period τ immediately after the polarity of the recording binary data is inverted (eg, inverted from “1” to “0”). Shown (this is the square wave recording used previously).

Since the polarity of the recording current is reversed, an asymmetric recording magnetic field having a polarity opposite to that of FIG. 4 is formed under the magnetic pole of the ring head. Under the magnetic pole L on the leading side, the magnetic recording medium is largely magnetized to the negative pole, and under the magnetic pole T on the trailing side, only the surface is magnetized to the positive pole. However, under the trailing side magnetic pole T, only the surface was slightly magnetized to the negative electrode in the state of FIG. 4, so that it returns to the original state, and it is a region where the magnetization strength is not reduced.

FIG. 9 shows a state slightly after generation of "0" (= reversal of polarity of recording current) of recorded binary data (conventional rectangular wave recording).

In the portion where "1" of binary data is recorded,
A region of W ₀₁ where the strength of magnetization is not reduced is formed. Further, a region having a width W ₀₂ in which the magnetization is strengthened is formed (this corresponds to the portion between the gap center and the trailing side magnetic pole T in FIG. 8). The widths W ₀₁ and W ₀₂ of these regions are narrower as compared with FIG. 7.

Therefore, according to the present invention, the widths W _T1 , W of FIG.
_The output level can be improved because _T2 is larger than the widths W ₀₁ and W ₀₂ shown in FIG. 9 according to the conventional technique.

The system in which no recording current is supplied during the current-off period τ has been described above. Of course, the same effect can be obtained by supplying a small current that cannot magnetize the magnetic recording medium.

FIG. 10 is a block diagram showing a main structure of a magnetic recording / reproducing apparatus according to the second embodiment of the present invention. In FIG. 10, components equivalent to those in FIG. The description is omitted. In FIG. 10, 8 is a recording system signal processing circuit, 9 is an equalization circuit, 10 is a clock reproduction circuit, 11 is a data identification circuit, and 12 is a reproduction signal system processing circuit.

This embodiment is an example applied to a system for recording / reproducing a video signal or an audio signal as a digital signal. At the time of recording, the recording data is converted into an error correction code and a synchronizing signal by a recording system signal processing circuit 8. After being added, it is modulated, converted into the waveform shown in FIG. 2C by the recording signal control circuit 2, and recorded on the magnetic tape 5 by the recording amplifier 3 and the recording head 4. At the time of reproduction, the signal reproduced by the reproducing head 6 is subjected to the intersymbol interference generated in the transmission system by the equalizing circuit 9, and then the clock reproducing circuit 10 reproduces the transmission clock from the reproduced signal. Data "1" or "0" is discriminated using this output clock, and the identification data and the clock are sent to the reproduction system signal processing circuit 12 in the next stage. The reproduction system signal processing circuit 12 can detect the synchronization signal, perform error correction processing, etc., and finally obtain the original recorded data string.

By recording / reproducing with this structure, for example, in a system with a bit interval T = 50 ns, a tape head relative speed of 5 m / s, and a shortest recording wavelength of 0.5 μm, the current off period τ = 35 ns and the magnetic tape 5 is used. According to the experiment using the current ME tape with the easy axis angle of about 20 °, the reproduction level of the shortest recording wavelength signal (10 MHz) is 1 to 2 dB with respect to the conventional rectangular wave recording, and the transmission system S / N is 0.5. .About.1.0 dB can be improved, and the error rate of the system can be improved by 1 to 2 digits in proportion to S / N.

It was also confirmed that the value of the current-off period τ was most effective when τ = 3T / 4 was selected for the bit interval T.

FIG. 11 is a block diagram showing a main structure of a magnetic recording / reproducing apparatus according to the third embodiment of the present invention. In FIG. 11, the same components as those in FIG. The description is omitted. In FIG. 11, 91, 92
Is an equalizer circuit, and 93 is a switch. The circuit operation of this embodiment is almost the same as that of the second embodiment shown in FIG. 10, except for the following points.

In this embodiment, at the time of recording, selection is made between the conventional rectangular wave recording and the current-off period τ, and the recording signal control circuit 2 performs recording by the selected recording method, and, for example, a recording data block. A flag that identifies this recording method is entered in the subcode of. Next, at the time of reproduction, the reproduction system signal processing circuit 12 operates to read the identification flag and control the switch 93 to select the waveform equalization circuits 91 and 92 suitable for the recording system.

In the recording method provided with the current-off period, the reproduction level is improved as the wavelength becomes shorter, so that the frequency characteristic of the transmission system is different from that of the rectangular wave recording. However, if the configuration of this embodiment is adopted, There is an effect that the system can be optimized by selecting an equalization curve suitable for each.

In this embodiment, two sets of equalization circuits 91,
Although 92 is provided, the circuit constant may be switched by one equalizing circuit 9.

Although the method of turning off the recording current for τ time when the recording data is inverted has been described above, the present invention is not limited thereto.

FIG. 12 shows a recording current waveform according to the fourth embodiment of the present invention. This is a recording current waveform conventionally known as pulse train recording. The pulse train has a regulation of current on / off time, whereas in the present invention, the current off period τ immediately before the inversion of recording data.
(○ in the figure) should be secured. Of course, Figure 1
As shown in 2, the current off period τ may be provided for each bit.

According to this current waveform, for example, in a fixed head type multi-track digital recording / reproducing apparatus, the total recording current can be reduced and the S / N can be improved at the same time.

Although the embodiment in which the NRZ digital signal is used as the recording signal has been described above, the present invention is not limited to this, and can be applied to recording by all modulation methods. As for the detection method at the time of reproduction, any method such as integration, differentiation, and partial response can be supported, but the effect is particularly great in the case of the integration detection method. It is considered that this is because the differential detection and partial response detection methods are easily affected by the phase distortion of the reproduced waveform.

Further, although the example in which the present invention is applied to the digital magnetic recording / reproducing apparatus has been described above, it is of course applicable to the conventional analog type magnetic recording / reproducing apparatus.

FIG. 13 is a block diagram showing a main structure of a magnetic recording / reproducing apparatus according to a fifth embodiment of the present invention. In FIG. 13, the same components as those in FIG. The description is omitted. In FIG. 13, 13 is a video signal generation circuit, 14 is an FM modulation circuit, 15 is an FM demodulation circuit, and 16 is a video signal generation circuit. This embodiment is an example of application to a conventional FM recording type VTR.

In the conventional analog VTR, at the time of recording, the recording signal converted by the video signal generating circuit 13 is FM-modulated by the FM modulating circuit 14, and then the recording amplifier 3,
Recording is performed on the magnetic tape 5 by the recording head 4. During reproduction, the signal reproduced by the reproducing head 6 is amplified by the reproducing amplifier 7 and then demodulated by the FM demodulation circuit 15.
The original video signal is obtained by the video signal generation circuit 16.

In general, a rectangular wave is used as the output signal of the FM modulation circuit 14 because of the simplicity of the circuit. Therefore, the output signal of the FM modulation circuit 14 is input to the recording signal control circuit 2 and fixed according to the present invention. By using the method in which the current-off period τ is provided for recording, the output level of the carrier signal is increased, and finally the video signal S / N can be improved.

FIG. 14 is a circuit diagram showing a concrete example of the recording current control circuit 2 used in each embodiment of the present invention. In FIG. 14, 1 is the above-mentioned recording signal input terminal, 2 is the above-mentioned recording signal control circuit, and 21, 22
Is a buffer, 23 is a delay circuit, 241-249 are resistors,
25 is a buffer, 26 is an adder / subtractor, 27 is an adder, 28
Is a recording signal control circuit output terminal.

FIG. 15 is an operation timing chart of the recording signal control circuit shown in FIG. The circuit operation of FIG. 14 will be described below with reference to FIG.

First, the original recording signal (a) expressed in binary is input from the input terminal 1 and the delay signal shown in (b) is obtained through the delay circuit 23. At the same time, the signal (a) is also input to the buffer 22, and the delayed signal (b) is subtracted from the output signal (c) by the adder / subtractor 26 to obtain the signal shown in (d). Finally, if the signal of (e) and the signal of (d) obtained through the buffer 25 of the delayed signal (b) are added by the adder 27, the recording current off period τ as shown in (f) is obtained.
A recording signal having the following is output to the recording signal control circuit output terminal 28. At this time, the recording current off period τ is delayed by the delay circuit 2
It is equal to the delay amount of 3, and an arbitrary time can be set.

In FIG. 14, the delay circuit 23 is composed of an analog delay line and termination resistors of the resistors 241 and 242, but the delay circuit 23 may be a digital type such as a shift register. The resistors 243 to 246 operate for addition and subtraction, and the resistors 247 to 249 operate for addition.
Further, the buffers 21, 22 and 25 are inserted for the purpose of stable operation of the circuit and are not always necessary.

The example in which the magnetic tape 5 is used as the magnetic recording medium has been described above, but the same effect can be obtained even when the medium is a disk. Further, although the recording head 4 and the reproducing head 6 are independently provided, it goes without saying that the recording / reproducing head may also be used.

[0053]

As described above, when the magnetic recording / reproducing apparatus of the present invention is used, the signal reproducing level in the short wavelength region is increased and the transmission system S
/ N can be improved. As a result, the error rate can be improved if the recording signal is a digital signal, and the reproduction image quality can be improved in the recording / reproduction of an analog video signal, for example.

[Brief description of drawings]

FIG. 1 is a block diagram showing a main configuration of a magnetic recording / reproducing apparatus according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing recording current waveforms according to the first embodiment of the present invention and a conventional technique.

FIG. 3 is an explanatory diagram showing recording magnetic field distributions corresponding to longitudinal recording, perpendicular recording, and oblique recording by a ring-shaped magnetic head.

FIG. 4 is an explanatory diagram showing a recording magnetization process immediately before reversal of a recording current direction according to the first embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a state of residual magnetization during a recording current off period according to the first embodiment of the present invention.

FIG. 6 is an explanatory diagram showing a recording magnetization process immediately after the end of the recording current off period according to the first embodiment of the present invention.

FIG. 7 is an explanatory diagram showing a recording magnetization process after reversing the direction of the recording current according to the first embodiment of the present invention.

FIG. 8 is an explanatory diagram showing a recording magnetization process immediately after reversing the direction of a recording current according to a recording method of a conventional technique.

FIG. 9 is an explanatory diagram showing a recording magnetization process after reversing the direction of a recording current by a conventional recording method.

FIG. 10 is a block diagram showing a main configuration of a magnetic recording / reproducing apparatus according to a second embodiment of the present invention.

FIG. 11 is a block diagram showing a main configuration of a magnetic recording / reproducing apparatus according to a third embodiment of the present invention.

FIG. 12 is an explanatory diagram showing a recording current waveform when the recording current waveform according to the fourth embodiment of the present invention is applied to pulse train recording.

FIG. 13 is a block diagram showing a main configuration of a magnetic recording / reproducing apparatus according to a fifth embodiment of the present invention.

FIG. 14 is a block diagram showing one specific example of a recording current control circuit applicable to each embodiment of the present invention.

15 is an explanatory diagram showing an operation timing of the recording current control circuit of FIG.

[Explanation of symbols]

 2 recording signal control circuit 3 recording amplifier 4 recording head 5 magnetic tape 6 reproducing head 7 reproducing amplifier 8 recording system signal processing circuit 9 equalizing circuit 10 clock reproducing circuit 11 data identification circuit 12 reproducing system signal processing circuit 14 FM modulation circuit 15 FM Demodulation circuit

Claims (6)

[Claims] 1. A magnetic recording medium having an easy axis of magnetization in an oblique direction or a perpendicular direction and a magnetic head are moved relative to each other, and recording currents having different polarities are respectively applied to "0" and "1" of recorded binary data. In the magnetic recording method of supplying the binary data to the magnetic head and recording the binary data on the magnetic recording medium, reversing the polarity of the recording current with a neutral level period τ in which the recording current is reduced without reversing the polarity. A magnetic recording method characterized by: 2. A magnetic recording / reproducing apparatus comprising a magnetic recording medium having an axis of easy magnetization in an oblique direction or a perpendicular direction, and a magnetic head for recording / reproducing binary data on the magnetic recording medium, at the time of data recording. , A recording signal control circuit for decreasing the recording current value for a predetermined period (τ) is provided, and the polarity of the recording current is reversed with a neutral level period τ for decreasing the recording current without reversing the polarity, A magnetic recording / reproducing apparatus characterized by supplying to a magnetic head for recording. 3. A magnetic recording medium having an axis of easy magnetization in an oblique direction or a perpendicular direction, a recording / reproducing head for recording / reproducing binary data on the magnetic recording medium, and a signal reproduced by the recording / reproducing head. A waveform equalizing circuit for removing intersymbol interference, a clock regenerating circuit for regenerating a transmission clock from an output signal of the waveform equalizing circuit, and a data discriminating circuit for discriminating data by the output clock signal of the clock regenerating circuit are provided. The magnetic recording / reproducing apparatus is provided with a recording signal control circuit that reduces the recording current value for a predetermined period (τ) during data recording, and the polarity of the recording current is sandwiched between neutral level periods τ that reduce the recording current without inverting the polarity. Is reversed and the recording current is supplied to the magnetic head for recording. 4. The waveform equalization circuit according to claim 3, wherein the waveform equalization circuit includes a first waveform equalization circuit and a second waveform equalization circuit, and indicates the presence or absence of the neutral level period τ during data recording. The magnetic recording medium is characterized by recording identification data on the magnetic recording medium and selecting either the first waveform equalization circuit or the second waveform equalization circuit according to the value of the identification data during reproduction. Recording / playback device. 5. A magnetic recording comprising a magnetic recording medium having an easy axis of magnetization in an oblique direction or a perpendicular direction, and a magnetic head for recording / reproducing an FM-modulated analog video signal or audio signal on the magnetic recording medium. In the reproducing apparatus, at the time of recording, a recording signal control circuit that reduces the recording current value of the carrier signal for a predetermined period (τ) is provided, and the polarity of the recording current is reduced with a neutral level period τ that reduces the recording current without inverting the polarity. Is reversed and the recording current is supplied to the magnetic head for recording. 6. The delay circuit according to claim 2, 3 or 5, wherein the recording signal control circuit delays an input recording signal by a predetermined time τ, and a subtraction circuit for subtracting an output signal of the delay circuit from the recording signal. And an adder for adding the output signal of the delay circuit and the output signal of the subtraction circuit, and the output signal of the adder is recorded.