JPH03100905A - Perpendicular magnetic recording system - Google Patents

Abstract

PURPOSE:To obtain self-synchronism even when data '0' appears in a row by simultaneously recording a current waveform for self-synchronism in an NRZI-FP recording system in a specified system. CONSTITUTION:In a waveform chart expressing a recording current in a perpendicular magnetic recording system, a pulse which is smeared in black means an additional pulse V or A for self-synchronism and a pulse which is ordinarily expressed means the data pulse D of data '1'. When four or more '0's appear in a row after the data pulse D or D', following additional recording is performed. Firstly, the pattern of 000V is inserted when four '0's appear in a row and the final D' of a series of pulses D has a polarity reverse to that of the pulse V before the pulse D. Secondly, the pattern of 0V00 is inserted when four '0's appear in a row and the last pulse D' of a series of data pulse preceding has a polarity same as that of the pulse V before the pulse D. Then, the pattern of 00V00 is inserted when five '0's appear in a row. Thirdly, the pattern of A00V is inserted when six or seven '0's appear in a row.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a perpendicular magnetic recording system using a ring head, and is particularly suitable for a PCM VTR.

[Conventional technology]

In recent years, a perpendicular magnetic recording method has been proposed as a magnetic recording method capable of realizing high-density recording, in which the magnetic layer of a magnetic recording medium is magnetized in a direction perpendicular to the medium surface. Various methods have been proposed for this perpendicular magnetic recording method, one of which is a perpendicular magnetic recording method that performs perpendicular magnetization using an annular ring head having one or more gaps.

In the conventional perpendicular magnetic recording method using a ring head, a square wave is recorded to produce magnetization as shown in Figure 12(a), and when this is reproduced, the reproduced waveform is as shown in Figure 12(b). The asymmetric dipulse (dlpul
se ), and in order to solve this problem, the inventor of the present application has developed a method for recording NRZI.
It has been proposed to alternately generate micropulses of positive and negative polarity each time data "1" is generated and record them as a recording current.

That is, instead of the conventionally used NRZ I recording current waveform shown in FIG. 13(a), the corresponding recording current waveform shown in FIG. 13(b) (hereinafter, for convenience, this recording current waveform will be used) NRZI-F P (foot pr
ints) recording waveform and a perpendicular magnetic recording method using a mata NRZI-FP recording waveform (referred to as NRZI-FP recording method).

As shown in Fig. 13(b), the NRZI-FP recording waveform has a configuration in which a pulse current with a small width is applied, which is positive when the NRZI recording waveform rises, and negative when it falls. . If the levels of these minute width pulses are +1 and -1, respectively, the current value between adjacent pulses is a neutral level (0). That is, NRZ I-
In the FP recording waveform, for any binary format signal to be recorded, a pulse of one polarity is always followed by a pulse of the opposite polarity, resulting in a pulse train in which the polarity changes alternately. The characteristics are that there is always a period between these pulses in which a neutral level (0 level) persists.

14 to 17 show how the perpendicular medium 6 (assumed to be an unrecorded medium) is perpendicularly magnetized by this FP recording waveform over time. 14(a), FIG. 15(a), FIG. 16(a), and FIG. 17(a) are recording current waveforms, and FIG. 14(b) and FIG. The magnetization patterns of the perpendicular medium 6 are shown in FIG. 16(b), FIG. 16(b), and FIG. 17(b).

As shown in FIG. 14(a), when the center of the gap 7c of the ring head 7 (having a leading 7a1, a trailing 7b, and a gap 7c) comes to the position shown in the figure, the NRZ I-FP recording waveform starts rising. , it is assumed that a positive current is applied to the ring head 7. As a result, the ring head 7 is excited, and magnetization of opposite polarity is formed on both sides of the position. Note that, since no current flows through the ring head 7 until the center of the gap 7c reaches the position, the current is not flowing through the ring head 7 until the center of the gap 7c reaches the position, so the position is to the left of the magnetization range of the ring head 7, that is, the position E.
The perpendicular medium 6 further to the left is not magnetized. A non-magnetized portion on the perpendicular medium 6 shows 0''.

Since the NRZ I-FP recording waveform is a waveform in which a pulse current with a minute width is passed, after the current is passed for a minute time (this time is T), a ring is generated as shown in Figure 15 (a). The power supply to the helad 7 is stopped. In the FP recording waveform, the current only returns to the Ov level and does not immediately reverse to the reverse polarity region, so no reversal of magnetization occurs. Therefore, the perpendicular medium 6 has a magnetization reversal position (Fig. (indicated by F), substantially symmetrical magnetization is formed on both sides thereof. This is clear from the explanation of the basic principle above.

On the other hand, in the case of the NRZI-FP recording method, since the current is zero at the center of the bit, as shown in Fig. 16(b)
And as shown in FIG. 17(b), no magnetization is formed in the perpendicular medium 6. Magnetization is formed when a minute width pulse current flows in the FP recording waveform, and at this time magnetization reversal position F.

Magnetization of opposite polarity is formed in narrow regions on both sides of H.

According to this NRZI-FP recording method, magnetizations of opposite polarity are simultaneously formed by the leading 7a and the trailing 7b, and the strength of the magnetization is approximately equal to each other because the magnetization is caused by the magnetic field generated from the same ring head 7. have. In other words, the respective magnetizations have symmetry with each other. Also, magnetization is formed in NRZI-FP.
Since this occurs only when a pulse current with a minute width of the recording waveform flows, even if the ring head 7 is displaced relative to the perpendicular medium 6, the trailing 5b will not erase the magnetization formed by the leading 5a. , the above reverse polarity is maintained. Furthermore, when considering the magnetized regions that constitute one bit (indicated by matte finish in Fig. 17(b)), the bit central region between adjacent magnetized regions (region indicated by G in Fig. 17(b)) is magnetized. Therefore, each magnetized region is not subjected to a demagnetizing field. Therefore, substantially symmetrical magnetization is formed on both sides of the magnetization reversal positions F and H, and when this perpendicular magnetic recording is reproduced, a reproduced waveform having symmetry can be obtained. This eliminates the need to perform waveform equalization (Hilbert transform, etc.) on the reproduced waveform on the reproduction circuit side.
The configuration of the reproducing circuit can be simplified.

Further, such an NRZI-FP recording waveform is, for example, the first
It can be easily created by a circuit that passes the NRZI recording current waveform through the circuit shown in FIG.

As mentioned above, the characteristic of the NRZI-FP recording current waveform is that pulses of opposite polarity occur repeatedly in response to changes in the polarity of the binary signal to be recorded, and there is always a pulse between the positive and negative pulses. It is to have a period (neutral to zero). Therefore, in the NRZ I-FP recording current waveform, a waveform in which positive or negative pulses are generated successively or in which a negative pulse is directly connected immediately after a positive pulse does not occur.

By making the recording current waveform have minute pulses that take a reverse polarity in response to the polarity reversal of the original signal waveform to be recorded, and a neutral level that connects them, the magnetization state is changed relative to the magnetization reversal position. It is possible to make it symmetrical, and the Goi pulse ratio can be made approximately 1 regardless of the conditions of the medium and the ring head.

In addition, a circuit that performs waveform equalization processing is not required, which simplifies the circuit configuration, and reduces the overall circuitry by:
! J adjustment is also unnecessary.

[Problem to be solved by the invention]

However, although the NRZ I method has a large phase margin,
If data "0" continues for a long time, nothing will appear on the reproduced waveform, making it impossible to extract the timing for self-synchronization during scrap production, which has the drawback of causing a read error.

Therefore, in order to obtain timing for self-synchronization, it is necessary to limit the longest interval without magnetization reversal (maximum magnetization reversal interval T).

The MFM method is known as a method that can take timing for such self-synchronization.

This changes from "0" to "1" as shown in Figure 19(a), the write current, the state of magnetization in Figure 19(b), and the readout voltage of the reproduced waveform in Figure 19(c). Sometimes, the recording current is reversed, and when two “0”s occur in a row, “0” is generated.
” and “0”.
Timing for self-synchronization can be easily determined. However, in the case of this method, the magnetization reversal for clock extraction formed at the data “0” and the magnetization reversal formed at the data “1”
The disadvantage is that the distinction between magnetization reversals due to degrees must be made on the time axis during demodulation, and the phase margin is halved.

In addition, in the case of a transmission signal with a large DC component in a PCM signal, the DC component constantly fluctuates over a short period of time. , the base values of the write currents are no longer aligned, causing malfunctions in pulse identification and reproduction.

Furthermore, in a PCM signal, even if the information writing density is the same, depending on the state of the bit pattern, pulses may be locally sparse or concentrated.

This causes a bit shift in which the peak value of the read voltage decreases or the phase in which information appears changes, but it is desired to effectively prevent this.

In the case of the NRZ I method, the maximum magnetization reversal interval T is infinite and a DC component exists, and especially in the case of perpendicular recording with a ring ax head, the reproduced waveform becomes an asymmetric dipulse, resulting in a large bit shift. There is.

In addition, in the NRZ I-FP method, it is DC-free, and in the case of perpendicular recording using a ring head, the playback waveform becomes a symmetrical GUI pulse, which is an improvement in that the bit shift is small, but the maximum magnetization reversal interval T aX was not valid for the point where is infinite.

The present invention was made to solve these problems, and is similar to the NRZI-FP method in that it does not include a DC component, has small bit shifts, and has low power consumption. An object of the present invention is to provide a perpendicular magnetic recording system that can easily extract a signal for self-synchronization during aX.

[Means for Solving the Problem] According to the present invention, data “1” of the binary signal to be recorded is
NRZI records information on a perpendicular magnetic anisotropic medium by supplying a minute data pulse whose polarity is reversed after a neutral level period every time a degree occurs to a ring head as a recording current.
-In the perpendicular magnetic recording system based on the FP recording system,
A continuous state of "0" is observed over the 7 bits after the data "1", and if four or more "0"s continue, additional pulses are added in the following pattern and supplied to the ring head. A perpendicular magnetic recording system is provided in which the information is recorded in a manner similar to that of the original, and self-synchronization information is obtained during reproduction.

This pattern is such that when the last of a series of data pulses "1" is opposite in polarity to the additional pulse inserted before the series of data pulses "1", the data "0"
000V for 4 to 7 (where ■ is an additional pulse of the same polarity as the data pulse immediately before or after), the last one of a series of data pulses "1" is the same as the data pulse of that series. When the polarity of the additional pulse inserted before the pulse '1° is the same, or when there is an additional pulse inserted after the series of data pulses "11", the number of data "01" is 0v00 . 5!;l:
oOV00 for 6 and 7 (, ■ is an additional pulse of opposite polarity to the preceding data pulse)
The pattern is V (where A and ■ are pulses of opposite polarity to the previous data pulse).

The shortest pulse interval T between the cater pulse and additional pulses of the same polarity and between adjacent additional pulses of the same polarity is the recording gap length of the ring head, g1, the relative speed of the perpendicular magnetic anisotropic medium to the ring head. It is preferable that it is selected so that the relationship T≧3 g/v is satisfied, where V is T≧3 g/v.

[For production]

Data “1” is followed by data “1” in the binary signal to be recorded.
When 0'' continues, additional recording is performed in an appropriate pattern according to the number of data in synchronization with the clock pulse, so self-synchronization is possible even when data 0# continues for a long time. You can get information. Therefore, the occurrence of data reading errors can be suppressed. Further, such a pattern does not include a DC component, has fewer malfunctions, and can reduce power consumption. Further, in the method of the present invention, the polarity of the data pulse of the original NRZ 1-FP waveform does not change at all.

Considering that in such additional recording, the magnetized portion in the medium is approximately equal to the gap length, selecting the shortest pulse interval T between pulses of the same polarity in additional recording to be approximately three times the gap length will eliminate the adverse effects of the pulses of the same polarity. However, in the method of the present invention, by defining the additional recording pattern to be inserted in accordance with this principle, this state is always maintained, and the adverse effects of pulses of the same polarity do not appear.

〔Example〕

Hereinafter, the perpendicular magnetic recording method according to the present invention will be explained in detail with reference to the mouth side.

FIG. 1 is a waveform diagram showing recording current waveforms according to the perpendicular magnetic recording method of the present invention. Although this figure is drawn in two stages for convenience, it is originally continuous.

The blacked-out pulses in the figure represent additional pulses ■ or A for self-synchronization, and the pulses in normal expression are data "1".
represents the data pulse D of .

In addition, if there are three or less "0#s" sandwiched between data pulses "1", these "1 degrees" are treated as a series of data pulses, and the last data pulse in this series of data pulses is used in the explanation. For convenience, it is written as D'.

According to FIG. 1, in the present invention, 0 is 4 after the data pulse.
If this continues for more than one time, some additional recording is performed.

First, as shown as ■ in FIG. 1, when there are four consecutive 0's and the last one D' of the preceding series of data pulses is opposite in polarity to the additional pulse V that precedes it, the voltage is 000 V. pattern is inserted. This additional pulse■
The polarity of the data pulse D is opposite to that of the data pulse D that immediately follows.

On the other hand, as shown by ■ in FIG. 1, there are four consecutive 0's, and the last one of the preceding series of data pulses D' has the same polarity as the preceding additional pulse V. Sometimes a pattern of 0v00 is inserted. In a similar case, if there are five consecutive 0's, an oovoo pattern is inserted.

The polarity of the additional pulse V in this case is opposite to that of the preceding data pulse.

Next, when 6 or 7 consecutive 0's occur, a pattern of A00V is inserted as shown as ■ in FIG. Note that the polarity of pulse A is opposite to that of the immediately preceding data pulse.

In this way, up to seven consecutive 0's have been observed, and as mentioned above, when the last data pulse in the series of data pulses has the opposite polarity to the preceding additional pulse, 000V (■), and when the polarity is the same, it is 1jtA00V (■). Then, the number of 0s following these patterns will be observed again over 7 bits, but at this stage there is no preceding data pulse, so when the number of remaining 0s is 4, it will be 0v.
oovoo when it is 00.5, A0 when it is 6 or more
Insert 0V (■). At this time, the polarity of the pulse A is opposite to that of the immediately preceding additional pulse V.

Thereafter, similar pattern insertion is repeated according to the remaining number of 0's to which these are applied, and continues until the number of remaining 0's becomes 3 or less. Therefore, if 0 continues for a long time, A
The pattern of 00V will be repeated.

In this way, in the present invention, the insertion pattern is determined to allow a maximum of three consecutive zeros, so the maximum magnetization reversal interval T is 4T, where T is the inter-bit aX interval.

Such a recording current waveform is applied to a ring head and written to a perpendicular medium as described below.

Figure 2 shows the NRZI method and NRZI- method for the same data.
For comparison, it is shown how the recording current waveforms obtained by the FP method and the NRZI-FP method according to the present invention differ.

The number written below each waveform is the cumulative value of digital values.
).

As can be seen from the above, in the method of the present invention, the maximum magnetization reversal interval T is suppressed to a certain level, and the DSV (max) is 2 or less, and no DC component is included.

Furthermore, in this method, the polarity of the recording current waveform relative to "1" in the original NRZI-FP method is maintained as it was.

Figure 3 shows the recording current waveform, magnetization pattern, reproduction waveform, and tilt direction detection waveform when an additional pulse is inserted in a pattern of A00V in the recording method of the present invention, and Figure 4 shows the conventional waveform with no additional pulse. Data "1" according to the NRZ 1-FP method is shown for comparison.

In the conventional NRZI-FP method, the reproduced waveform always becomes dipulses of alternating polarity as shown in FIG. 4, but in the method of the present invention, dipulses of the same polarity appear by inserting additional pulses, and as a result, During reproduction, when reproduced waveforms having the same slope direction are observed, data pulses and other pulses can be distinguished according to a predetermined algorithm, and pulses other than data pulses can be used for timing. can.

In this case, in the method of the present invention, positive pulses and negative pulses can be freely selected based on the 0 level, so by giving information to the polarity of the pulse, it is possible to combine the data pulse and the data pulse while keeping the phase margin equal to that of the NRZ I method. You can distinguish the pulses added for black and white.

Next, consider at what intervals such additional pulses should be generated.

When DC excitation is applied to a perpendicularly anisotropic medium using a ring head, two magnetizations of equal magnitude and opposite polarity are recorded, as shown in FIG. The length LH of one magnetized region is approximately equal to the gap length g.

In the NRZI-FP recording method, the polarity of the recording current pulses is alternately reversed, so as shown in Figure 6, the leading-side magnetization IL of the 1st bit becomes trailing when recording the magnetization of the 2nd bit. It is overwritten with magnetization 2T of the same polarity on the side. Therefore, there is no problem with consecutive recording current pulses of opposite polarity separated by the gap length.

On the other hand, when recording current pulses of the same polarity appear as in the present invention, the additional pulse V and the data pulse D are close to each other as shown in FIG.
When approaching twice as much, the magnetic field on the leading side DL due to the data pulse and the trailing side VT due to the additional pulse ■
Magnetization reversal is formed at the magnetization boundary due to the magnetic field.

Because this magnetization reversal causes pseudo data to be recorded where no data originally exists, it is necessary to avoid such a situation.

Therefore, the shortest pulse interval T must be T > 2 g/v, where g1 is the recording gap length of the ring head and V is the relative speed of the perpendicular magnetic anisotropic medium to the ring head. It is necessary that T≧3 g/v.

Note that the speed V is for adjusting the dimensions.

Therefore, when pulses of the same polarity continue, it is necessary to insert two or more 0s between them, and this condition is maintained by inserting additional pulses as described above.

FIG. 8 is a block diagram showing a circuit for perpendicular magnetic recording used in the present invention.

Input binary data is input to an encoder, where positive pulses and negative pulses are created according to a predetermined algorithm, which are combined by an adder 12 and applied to a recording current generation circuit 13. The recording current generated here is supplied to the ring head to perform perpendicular magnetic recording.

The algorithm for generating additional patterns in the encoder can be summarized as follows.

(1) When the polarity of the immediately preceding data pulse is opposite to the polarity of the additional pulse preceding the series of data pulses, and the number of 0s is from 4 to 7, it is set to 000V.

(2) If the polarity of the immediately preceding data pulse is the same as the polarity of the additional pulse preceding the series of data pulses, or there is no immediately preceding data pulse, and the number of 0s is 4, it is set to 0v00.

(3) If the polarity of the immediately preceding data pulse is the same as the polarity of the additional pulse that precedes the series of data pulses, or there is no immediately preceding data pulse, and the number of zeros is 5, oovoo is determined.

(4) If the polarity of the immediately preceding data pulse is the same as the polarity of the additional pulse that precedes the series of data pulses, or there is no immediately preceding data pulse, and the number of zeros is 6 or 7, A00V. do.

(5) When 0's continue for a longer time Since 000v or AQOV is inserted by the above algorithm, count the number of subsequent 0's up to 7 and apply (2) to (4).

FIG. 9 is a block diagram showing a schematic configuration of a circuit ρ used in the present invention for reproducing information from a recording medium on which perpendicular magnetic recording has been performed.

Symmetrical dipulse 31 taken out by ring head 21
A zero-crossing pulse 32 is extracted by a zero-crossing detector 22, while a monopulse 33 is obtained by an integrating circuit 23. From this monopulse 33, a positive pulse 34 and a negative pulse 35 are extracted by a positive pulse gate generator 24 and a negative pulse gate generator 26, respectively, which are comparators. And positive pulse 3
Zero cross waveform 32 to gate 25 with 4 as window
When passed through, the data pulse 36 is extracted, and similarly, when the zero-crossing waveform 32 is passed through the gate 27 using the negative pulse 35 as a window, an additional pulse 37 is extracted. These data pulses 36 and additional pulses 37 are taken out from the decoder 28 as binary data outputs.

In order to distinguish between the data pulse D and the additional pulses V and A from the waveform recorded in the pattern shown in FIG. 1, the algorithm of the decoder is as follows.

When pulses of the same polarity appear consecutively (1)
When the number of 0s between pulses of the same polarity is 3, the second pulse is an additional pulse.

(2) When the number of 0s between pulses of the same polarity is 2 (a
) When a pulse exists immediately before the first pulse, both the first and second pulses are considered as additional pulses.

(b) When there is no pulse immediately before the first pulse The first pulse is an additional pulse.

FIG. 10 shows a list of various modulation methods, and it can be seen that the method of the present invention is capable of self-synchronization and does not include a DC component.

Although rectangular minute pulses are used in the embodiments described above, the present invention is limited to this, and a sawtooth pulse waveform as shown in FIG. 11 may also be used. By changing the pulse waveform from a rectangular shape in this manner, the current applied to the ring head can be controlled within a predetermined pulse width T. Therefore, by appropriately controlling this pulse waveform, it is possible to further improve the symmetry of the magnetization formed on both sides of the magnetization reversal position.

Further, although the present invention is applied to the NRZI-FP method, it can also be applied to other modulation methods that cannot perform self-synchronization.

Further, in the present invention, a long series of 0's is replaced with a pattern of A00V, but the number of intermediate 0's is arbitrary, and a pattern such as A000 V may be used as a basic pattern.

〔Effect of the invention〕

According to the perpendicular magnetic recording method according to the present invention, NRZ I
- In the FP recording method, since the current waveform for self-synchronization is recorded at the same time, self-synchronization can be obtained even when data "0" is continuous, improving the reliability of readout. I can do it.

Furthermore, in the method of the present invention, the features of the NRZI-FP method, such as the write current waveform containing no DC component, low power consumption, and small bit shift, are maintained.

[Brief explanation of drawings]

FIG. 1 is a waveform diagram showing a recording current waveform according to an embodiment of the present invention, and FIG. 2 is a recording current waveform in each of the NRZ I method, the NRZl-FP method, and the NRZI-FP method according to the present invention 1. FIG. 3 is an explanatory diagram showing the recording current waveform, magnetization pattern, reproduction waveform, and tilt direction detection waveform according to the method of the present invention. FIG. 4 is the same as FIG. 3 in the NRZl-FP recording method. FIG. 5 is an explanatory diagram showing the relationship between the magnetization pattern and the gap length. FIG. 6 is an explanatory diagram showing the case where two current waveforms with different polarities appear in adjacent bits. FIG. 7 is an explanatory diagram showing the relationship between the magnetization pattern and the gap length. have the same polarity 2
An explanatory diagram showing the case where two current waveforms appear in adjacent bits, FIG. 8 is a block diagram showing the recording system used in the present invention, FIG. 9 is a block diagram showing the playback system, and FIG. 10 is a block diagram showing various types of modulation. A chart comparing the methods; FIG. 11 is a waveform diagram showing a sawtooth wave used as a write current waveform; FIG. 12 is an explanatory diagram of an asymmetric dipulse in perpendicular magnetic recording;
Fig. 13 is a comparative explanatory diagram of the NRZI method and NRZI-FP method, and Figs. 14 to 17 are conventionally proposed N
An explanatory diagram showing how magnetization is formed over time by the RZI-FP method, Fig. 18 is a circuit diagram showing a circuit for generating an NRZ I-FP multiplied signal, and Fig. 19 is an explanatory diagram showing the MFM method. be. 6... Perpendicular magnetic recording medium, 7,14.21... Ring head, 11... Encoder, 12... Adder,
13... Recording current generation circuit, 22... Zero cross detector, 23... Integrator, 24... Positive pulse gate,
'25...Gate, 26...Negative pulse gate, 27
...gate, 28...decoder.

Claims (1)

[Claims] 1. A minute data pulse whose polarity is reversed after a neutral level period is supplied to the ring head as a recording current every time data "1" is generated among the binary signals to be recorded, and the perpendicular magnetic In the perpendicular magnetic recording method based on the NRZI-FP recording method that records information on an anisotropic medium, a continuous state of "0" was observed over the 7 bits after the data "1", and four "0"s were observed. In this perpendicular magnetic recording method, additional pulses are supplied to the ring head in the following pattern to obtain self-synchronization information during playback. 000V for 4 to 7 (where V is or an additional pulse of the same polarity as the immediately following data pulse)
pattern, when the last of a series of data pulses “1” is of the same polarity as the additional pulse inserted before that series of data pulses “1”;
”, the number of data “0” is 0V00 for 4 and 00V0 for 5.
0 (however, V is an additional pulse of opposite polarity to the preceding data pulse), A00V pattern for 6 and 7 (however, A and V are pulses of opposite polarity to the immediately preceding data pulse). 2. The shortest pulse interval T between the data pulse and additional pulses of the same polarity and between adjacent additional pulses of the same polarity is such that the recording gap length of the ring head is g, and the recording gap length of the perpendicular magnetic anisotropic medium is relative to the ring head. 2. The perpendicular magnetic recording system according to claim 1, wherein the perpendicular magnetic recording system is selected so that the relationship T≧3g/v is satisfied, where v is the relative velocity.