JPH03100904A - Perpendicular magnetic recording system - Google Patents

Abstract

PURPOSE:To obtain self-synchronum even in the case that data '0' continues by simultaneously recording a current waveform for self-synchronism in an NRZI-FP recording system. CONSTITUTION:In a waveform chart expressing a recording current in a perpen dicular magnetic recording system, a pulse which is smeared in black means an additional pulse V for self-synchronism, a normal pulse N which is paired with the pulse V and has a polarity opposite to the pulse V and a data pulse. Then, a pulse which is ordinarily expressed means the data pulse D of data '1'. According to the waveform chart, when six '0's continue after the pulse D, the V pulse is inserted before the third '0' and the N pulse is inserted before the fourth '0'. When six or more '0's continue, the VN is repeated further. Namely, when '0's continue, the pattern of 00(VN)n00 ((n) means the repetition of the pattern of VN) is repeated. Thus, reliability in readout is improved.

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). An asymmetrical dipulse with respect to the origin
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 it 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) NRZ I-F P (f'oot
prints) Recording waveform, also known as NRZ I-
NRZ 1- is a perpendicular magnetic recording method using FP recording waveform.
FP recording method) is used.

As shown in FIG. 13(b), the NRZI-FP recording waveform has a configuration in which a pulse current with a small pulse width is positive at the rising edge of the NRZI recording waveform and negative at the falling edge. There is. 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
- The FP recording waveform is a pulse train in which the polarity alternates, with a pulse of one polarity followed by a pulse of the opposite polarity, regardless of the signal to be recorded in any binary format. , and 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. What is shown in FIG. 16(b), FIG. 16(b), and FIG. 17(b) are the magnetization patterns of the perpendicular medium 6.

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 NRZI-FP recording waveform starts rising. , it is assumed that a positive current is applied to the ring head 7. As a result, the ring rod 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 vertical medium 6 further to the left is not magnetized. A non-magnetized portion on the perpendicular medium 6 shows "0".

Since the NRZI-FP recording waveform is a waveform in which a pulse current with a minute width is passed, it takes a minute time (this time is denoted as T).
After the current has been passed for a period of time, the current supply to the ring pad 7 is stopped as shown in FIG. 15(a). 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 NRZ I-FP recording method, magnetizations of opposite polarity are simultaneously formed by the leading 7a and trailing 7b, and their strengths are almost equal because they are caused by the magnetic field generated from the same ring head 7. It has a certain quality. In other words, the respective magnetizations have symmetry with each other. Moreover, magnetization is formed in NRZ I-
This occurs only when a pulse current with a minute width of the FP recording waveform flows, so 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 reverse polarity described above is maintained. Furthermore, the magnetized region constituting one bit (Fig. 17(b)
)), the center region of the bit between adjacent magnetized regions (region marked G in Figure 17(b)) is not magnetized, so each magnetized region is subject to a demagnetizing field. There is no such thing. 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 C, a reproduced waveform having symmetry can be obtained. This eliminates the need to perform waveform equalization (such as Hilbert transformation) on the reproduced waveform on the reproduction circuit side, and the configuration of the reproduction circuit can be simplified.

Further, such an NRZ I-FP recording waveform is obtained by passing the NRZ I recording current waveform through the circuit shown in FIG. It can be easily made by

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 NRZI-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. The dipulse ratio can be made approximately 1 regardless of the conditions of the medium and the ring head.

Further, since a circuit for performing waveform equalization processing is not required, the circuit configuration can be simplified, and there is no need to adjust the entire circuit.

[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 appears on the reproduced waveform, making it impossible to extract the timing for self-synchronization during reproduction, which has the drawback of causing a read error.

Therefore, in order to be able 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 FIG. 19(a) for the write current, FIG. 19(b) for the state of magnetization, and FIG. 19(c) for the readout voltage of the reproduced waveform. The recording current is reversed when the current changes to 0, and the recording current is reversed at the boundary between "0" and "0" when two "0"s occur in a row, making it easy to set the timing for self-synchronization. I can do it. However, in the case of this method, it is necessary to distinguish between the magnetization reversal for clock extraction formed at data "0#" and the magnetization reversal caused by data "1" on the time axis during demodulation, and the phase The disadvantage is that the margin is cut in half.

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 NRZI method, the maximum magnetization reversal interval Tl1ax
is infinite and there is a DC component, and especially in the case of perpendicular recording using a ring head, the reproduced waveform becomes an asymmetrical dipulse, resulting in a problem of large bit shifts.

In addition, in the NRZ I-FP method, it is DC-free, and in the case of perpendicular recording using a ring head, the reproduced waveform becomes a symmetrical dipulse and the bit shift is small, which is an improvement, 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 NRZ I-FP method in that it does not include a DC component, has small bit shifts, and has low power consumption.
It is an object of the present invention to provide a perpendicular magnetic recording system that allows easy extraction of signals for self-synchronization during reproduction by limiting .

[Means to solve the problem]

According to the present invention, among the binary signals to be recorded, data “1”
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 it occurs as a recording current to a ring head.
-In the perpendicular magnetic recording system based on the FP recording system,
When data "0" continues, an additional pulse current synchronized with the clock signal timing is (VN)n (V is an additional pulse, N is a normal pulse that is paired with this additional pulse and has the opposite polarity to the additional pulse, n represents repeating the pattern of (VN)), and the polarity of the pulse V is the same as that of the preceding data pulse, and the pulse N
The data pulse and the following data pulse are supplied to the ring head and recorded so as to have the same polarity, thereby obtaining self-synchronization information during reproduction.

In these cases, the shortest pulse interval T between the data pulse and the additional pulse and between the normal pulse and the next data pulse
where the recording gap length of the ring head is g1 and the relative speed of the perpendicular magnetic recording system to the ring head is V.
It is preferable that it is selected so that the relationship is ≧3 g/v.

[For production]

Data “1” is followed by data “1” in the binary signal to be recorded.
If 0's continue, additional recording is performed at an appropriate lock timing position in a pattern of (VN)n, so even if data 0's continue for a long time, self-synchronization information can be saved. Therefore, it is possible to suppress the occurrence of data reading errors.In addition, such a pattern does not include a DC component, so malfunctions are less likely to occur, and power consumption can be reduced.Furthermore, the present invention In this method, the polarity of the data pulses of the original NRZ I-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, the shortest pulse interval T between a data pulse of the same polarity and an additional pulse, and between a normal pulse and the next data additional pulse is defined as the gap length. It may be selected to be about three times as large.

〔Example〕

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

FIG. 1 is a waveform diagram showing recording current waveforms according to the perpendicular magnetic recording method of the present invention. The blacked-out pulses in the figure represent the additional pulse V for self-synchronization and the normal pulse N that is paired with this and has the opposite polarity to the additional pulse, and the pulse in normal expression represents the data pulse D with data "1". .

According to FIG. 1, when six 0's follow a data pulse, a V pulse is inserted as the third pulse, and an N pulse is inserted as the fourth pulse. Further, when 0 continues longer than that, VN is further repeated. Further, when 0 continues longer than that, VN is further repeated. In other words, for a series of O, 00 (VN)
Repetitive replacement is performed in the noo(7) pattern. In this case, the ■ pulse has the same polarity as the D pulse that precedes it, but the last N pulse and the D pulse that follows have the same polarity. Therefore, in this embodiment, the maximum magnetization reversal interval T is 6 T b, where T is the bit interval.

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

Figure 2 shows the NRZI method and NRZI- method for the same data.
FP method, NRZ I-FP method according to the present invention (first
This figure shows for comparison how the recording current waveforms obtained depending on the pattern shown in the figure differ. The number written below each waveform is the cumulative value of digital values D
SV (DigitalSum Value). 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 value ax or less, and the DSV is 2 or less, and no DC component is included. Further, since the pulse inserted instead of 0 always has a VN pattern, the recording current waveform for "1" in the original NRZ I-FP method does not change at all.

Figure 3 shows the recording current waveform, magnetization pattern, reproduction waveform, and tilt direction detection waveform when additional pulses are inserted in a 0OVN pattern in the recording method of the present invention, and Figure 4 shows the waveforms without additional pulses. Similar content according to the conventional NRZ I-FP method is shown for comparison.

In the conventional NRZI-FP method, the reproduced waveform is always a dipulse of alternating polarity as shown in Fig. 4, but in the method of the present invention, dipulses of the same polarity appear by inserting an additional pulse, and as a result, the reproduced waveform is Sometimes, 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. .

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 providing information on the polarity of the pulse, the data pulse and clock can be adjusted while keeping the phase margin equal to that of the NRZI method. It is possible to distinguish the pulses added for use.

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 . Two magnetizations are recorded. The length LH of one magnetized region is approximately equal to the gap length g.

In the NRZ I-FP recording method, the polarity of the recording current pulses is alternately reversed, so as shown in Figure 6, the magnetization IL on the leading side of the 1st bit becomes the trailing side when recording the magnetization of the 2nd bit. It is overwritten by magnetization 2T of the same polarity on the ring 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 noxle V
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 ring-to-rad recording gap length and V is the relative speed of the perpendicular magnetic anisotropic medium to the ring head. It needs to be ≧3g/V.

Note that the speed V is for adjusting the dimensions.

Therefore, the additional pulse V and the normal pulse N are 00 (VN
)noO or 00 (VN) n000 pattern.

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.

FIG. 9 is a block diagram showing a schematic configuration of a circuit 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.

The data pulse D1 normal pulse N1 additional pulse V can be distinguished from the waveform recorded in the pattern shown in FIG. 1 as follows. When pulses of the same polarity appear successively, the pulse of the same polarity after the data pulse is a ■ pulse, and the pulse of opposite polarity repeated after the pulse of ■ is an N pulse, which continues until the next pulse of the same polarity appears (VN All pulses of opposite polarity in the pattern can be ignored as additional pulses, and the next time a pulse of the same polarity appears, that pulse can be recognized as a data pulse.

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

In the embodiments described above, a pattern of 00 (VN)n00 has been described, but the present invention is not limited to this, and the number of 0s before and after VN can be any number of 2 or more. Also, 00 (V
Patterns such as ON)noO and 00 (VOON)n00 can be adopted, and in the case of such patterns, the worst pattern can be avoided, so that so-called bit shifts in which the bit width fluctuates can be reduced.

Further, although rectangular minute pulses are used in the above-mentioned embodiments, the present invention is not limited to this.
A sawtooth pulse waveform as shown in the figure 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.

In addition, in the embodiment, in order not to change the polarity of the data pulse in the original NRZI-FP method, VN was always repeated to add an even number of pulses, but the additional pulse was set to an arbitrary integer of 2 or more and the final pulse was added. The additional pulse and the next data pulse may have the same polarity.

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.

〔Effect of the invention〕

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

Moreover, in the method of the present invention, the features of the NRZl-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 waveform diagram showing a recording current waveform according to an embodiment of the present invention.
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. An explanatory diagram showing the same thing as FIG. 3 in the NRZI-FP recording method for comparison, and FIG. 5 is an explanatory diagram showing the relationship between the magnetization pattern and the gap length. Figure fs6 is an explanatory diagram showing the case where two current waveforms with different polarities appear in adjacent bits, and Figure 7 shows two current waveforms with the same polarity.
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. Figure 11 is a waveform diagram showing a sawtooth wave used as a write current waveform, Figure 12 is an explanatory diagram of an asymmetric dipulse in perpendicular magnetic recording, and Figure 13 is a diagram comparing the NRZI method and NRZI- Comparative explanatory diagrams of the FP method, Figures 14 to 17 are conventionally proposed NR
An explanatory diagram showing how magnetization is formed over time using the Z I-FP method, FIG. 18 is a circuit diagram showing a circuit for generating an NRZI-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, when data “0” continues, an additional pulse current synchronized with the clock signal timing is applied to the data (VN)n (V is An additional pulse, N is a normal pulse that is paired with this additional pulse and has a polarity opposite to that of the additional pulse, n represents repeating the pattern of (VN)), and the polarity of the pulse V is the same as the preceding data. A perpendicular magnetic recording system in which the pulse N and the following data pulse have the same polarity and are supplied to the ring head for recording to obtain self-synchronization information during reproduction. 2. The shortest pulse interval T between the data pulse and the additional pulse and between the normal pulse and the next data pulse is the recording gap length of the ring head, g, and the relative speed of the perpendicular magnetic anisotropic medium with respect to the ring head. 2. The perpendicular magnetic recording system according to claim 1, wherein the perpendicular magnetic recording method is selected so that the relationship T≧3g/v is satisfied, where v is T≧3g/v.