JPH03219414A - Data surface servo system - Google Patents

Abstract

PURPOSE:To reproduce a playback signal of an opposite head in a gap-null frequency without any interference by shifting a data head and a servo head in blind sector area from each other. CONSTITUTION:The head 41 for servo signal reproduction and head 42 for data signal reproduction are mounted on the slider 46 as a rigid body. Both the heads 41 and 42 are arranged in a track width direction or longitudinally in a medium travel direction. The lower layer of the magnetic layer of a medium 43 is for servo signal recording and the upper layer is for data signal recording. When the servo head 41 is positioned right on a servo track 44, the data head 42 writes a signal on a data track 45 and then information on the data track 45 can accurately be reproduced at all times by tracking the servo track 44 by the servo head 41.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to technology for increasing track density in magnetic recording devices, and is a technology for achieving high track density and highly accurate positioning that has never been seen before. This is a basic technology. Therefore, it is a technology that can be widely applied to all fields of magnetic recording devices, such as magnetic disk devices, floppy disk devices, magnetic tape devices, and magnetic card devices.

[Conventional technology]

In order to accurately reproduce information on the recording medium-H, the signal conversion element, that is, the magnetic head, must be precisely positioned at the target signal recording position on the medium. However, as the track density increases, positioning becomes extremely difficult, so it is desirable to have a servo signal for positioning very close to the target data track. This concept of data plane (4) servo is reflected in systems called sector servo and embedded servo in magnetic disk devices, floppy disk devices, etc. using co-rotating media. By the way, in the sector servo method, the number of sectors greatly affects positioning accuracy, and the servo band is also narrowed. Furthermore, since it is not a continuous servo method, the embedded servo method is more desirable.

In the embedded servo method, IEEE Transaction on Magnetics (IEEE Transa
ction on Magnetics) Mag-1
As shown in 76, the recording frequency of the data signal on the upper layer of the recording medium is several megahertz, and the recording frequency of the servo signal on the lower layer is several hundred kilohertz, and the frequency bands are divided so that both signals can be accurately separated. .

[Problem to be solved by the invention]

However, in the above technique, since the servo signal is clearly separated from the data signal, it is difficult to provide a wide band for the servo signal. If the band of the servo signal cannot be secured, the positioning resolution will be limited to that band, so there is a possibility that the positioning accuracy (5) will deteriorate when the track width becomes narrow.

An object of the present invention is to provide a method for writing servo signals at high frequency in an embedded servo system that is a continuous servo system.

[Means to solve the problem]

The above objective can be achieved as follows. It is known that, as a reproduction characteristic of an inductive magnetic head having a certain gap length, a dead zone occurs when the signal recording wavelength on the medium is an integral multiple of the gap length. If the gap length differs, a corresponding dead zone region will occur. Therefore, by shifting the dead zone regions of the data head and the servo head, it becomes possible to reproduce the reproduction signals of the other party at their respective dead zone wavelengths, that is, the gap null frequency, without interfering with each other. At this time, it is desirable that the recording frequency of the servo signal is higher than the recording frequency of the data signal due to reproduction characteristics.

[Effect]

It is assumed that two heads, one for servo signal reproduction and one for data signal reproduction, are mounted on the same actuator (6). A servo signal and a data signal are recorded on the medium at respective recording wavelengths that are related to the gap length of the head. When the servo head reproduces a servo signal, the reproduction wavelength at that time has a size corresponding to the gap null of the data head, so the servo head does not detect the data signal.

The actuator can perform accurate positioning using the reproduced servo signal. Next, when the data head reproduces the data signal, the reproduction wavelength at that time has a size corresponding to the gap null of the servo head, so the data head does not detect the servo signal. Therefore, a high quality data signal can be reproduced.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing the basic idea of the present invention.

Generally, head gap loss is a function of gap length g and recording signal wavelength λ, and is expressed as follows.

(7) If the horizontal axis is the gap length g and the ratio g/λ of the recorded signal wavelength λ, and the vertical axis is the gap loss Lg, then the gap loss characteristic of the data head, for example, is as shown in curve 11. . Here, the gap length of the servo head is narrower than the gap length of the data head, so the horizontal axis in FIG. 1 has a shape in which the horizontal axis of the data head is expanded compared to the horizontal axis of the servo head. When drawn on the same graph as curve 11, what is shown by curve 12 becomes the gap loss characteristic of the servo head. Since the horizontal axis is an amount inversely proportional to the recording wavelength when the gap length is constant, it is proportional to the reproduction frequency.

Here, when the gap loss is not taken into account, the frequency characteristics of the reproduced signal are as follows: As shown in Figure 2, the signal amplitude decreases due to the thickness of the medium, and the signal amplitude decreases due to the spacing between the medium and the spacing gap. is included in the high frequency region, 6
It has a characteristic of dB10ct. Therefore, the frequency characteristic of the reproduced signal amplitude when gap loss is considered is the sum of the characteristics shown in FIG. 1 (8) and FIG. 2, and is as shown in FIG. As shown, the envelope of the curve becomes horizontal above a certain frequency.

By the way, since the reproduced signal does not read a signal whose output is smaller than a predetermined threshold value, the signal cannot be reproduced in the vicinity of the gap null. That is, the data head cannot reproduce data signals in area 12a in FIG. 1, and the servo head cannot reproduce servo signals in area 11a. Therefore, in FIG. 3, the frequency characteristic of the data signal on the medium is expressed by curve 3.
1. If the frequency characteristic of the servo signal is represented by curve 32, when the reproduction frequency of the data signal is f, the signal is reproduced without being interfered with by the servo signal. Servo signal reproduction frequency f
When s, the signal is reproduced without being interfered with by the data signal.

FIG. 4 is a diagram schematically showing a specific application example of the embodiment of the present invention. The servo signal reproducing head 41 and the data signal reproducing head 42 are both on the same rigid body.
For example, it is mounted on the slider 46-H. Both heads do not need to be arranged side by side in the track width direction (9), and may be arranged vertically in the medium running direction. The magnetic layer of the medium 43 has a lower layer for recording servo signals and an upper layer (surface layer) for recording data signals. When the servo head 41 is exactly positioned on the servo track 44, the data head 42 writes a signal to the data track 45, so that the information on the data track 45 is always kept as long as the servo head 41 tracks the servo track 44. be played accurately. The data signal may be written on the upper layer of the servo track 44,
The servo signal may be written in the lower layer of the data track 45. In this way, the entire surface of the medium can be used efficiently.

FIG. 5 is a diagram schematically representing another specific embodiment of the present invention. The servo signal reproducing head 51 and the data signal reproducing head 52 are both mounted on the same rigid body, for example, on a slider 56-H. Both heads are
It is not particularly necessary to arrange them side by side in the track width direction, and they may be arranged vertically in the medium running direction. The medium 53 is a (10) medium with an uneven surface, where the convex portions correspond to data tracks and the concave portions correspond to servo tracks. The magnetic layer in the convex portion is used for recording data signals, and the magnetic layer in the concave portion is used for recording servo signals. When the servo head 51 is positioned exactly on the servo track 54, the data track 55 is
This information can always be accurately reproduced if the servo head 51 tracks the servo track 54. Further, with such a medium structure, adjacent data tracks are physically separated (discrete), so adjacent signals are less likely to enter as noise components, and high quality of data signals is maintained. It is more convenient for the quality of the servo signal to cover the entire lower layer as shown in FIG.

The width ts of the servo head in the track direction in FIGS. 4 and 5 does not need to be equal to the width ta of the data head; positioning accuracy can be improved by making it wider or by making the servo signal multiphase. can be done.

(11) When this embodiment is adopted in a system using a disk-shaped recording medium such as a magnetic disk device, care must be taken regarding the range of the writing frequency. That is, in a disc-shaped recording medium, when the writing frequency is constant, the recording wavelength changes depending on the radial position, so the value of g/λ in FIG. 1 changes. For example, in an apparatus having a medium surface area in which the ratio of the outermost radius to the innermost radius is 1.5, when the writing frequency is constant, the recording wavelength λ changes by a factor of 1.5 between the inner and outer radii.

Therefore, gd/λ of the data signal is, for example, 0.5〈(gd
/λ)<0875, and assume that gs/λ of the servo signal changes within a range of 1.2<(gs/λ)<1.8.

That is, the values of a and b in the data head are 0.5 and 0.75, respectively, and the values of C2d in the servo head are 1.2 and 1.8, respectively. Here, at a certain radial position, the reproduction of the servo signal uses a servo head with a gap length approximately equal to the write signal wavelength at the first gap null of the data head, so that gs'Fλ−
It is. Similarly, data signal reproduction uses a data head with a gap length approximately equal to the write signal wavelength at the first gap null of the servo head, so g, cape λS. fs>
If fa, then λs x λd, so inevitably g
s > g, d.

The above techniques can be commonly applied to longitudinal recording and perpendicular recording, but in particular, in the case of a perpendicular recording head, the gap null region shown in FIG. 1 appears conspicuously, so it is suitable for the present invention.

FIG. 7 is a diagram showing another embodiment of the present invention.

Similar to FIG. 3, the horizontal axis shows the frequency and the vertical axis shows the reproduction output. When reproducing a signal using a servo head and a data head with the same gap length as mentioned above, we focused on the fact that the reproduction frequency ranges of both heads are different, and passed the reproduction signal of the data head to a low-pass filter, and then the reproduction signal of the servo head. Each signal is passed through a bypass filter. That is, the frequency ft
The curve 71 can be divided into the data signal characteristics and the curve 72 can be divided into the data signal characteristics with h as the boundary, and by using the shaded areas for each, the signals (13) do not interfere with each other.

FIG. 8 is a diagram showing the properties of the magnetic films of the data signal recording layer and the servo signal recording layer of the medium to which the present invention is applied. The horizontal axis represents the data linear recording density, and the vertical axis represents the reproduction output. The magnetic properties of the data layer are shown as curve 81. Here, the data signal uses a recording density in the area of Da. On the other hand, the magnetic properties of the servo layer are shown as a curve 82. Here, since the servo signal recording layer is below the data layer, there is a spacing loss and the actual curve 83
The characteristics are shown in . The servo signal uses the recording density of the area D5. In order to obtain such characteristics, it is desirable that the coercive force of the servo layer is larger than that of the data layer, and the saturation magnetization is about the same or the saturation magnetization of the servo layer is slightly larger.

[Effects of the Invention] According to the present invention, the servo band can be sufficiently increased,
Moreover, since the servo is continuous, a positioning system with very high quality servo signals can be obtained. This greatly contributes to (14) higher performance of the positioning servo system of the magnetic recording device.

[Brief explanation of drawings]

FIG. 1 is a graph showing the basic idea of the present invention, FIG. 2 is a graph showing the frequency characteristics of the reproduction output of magnetic recording, and FIG. 3 is a graph of the reproduction output of the magnetic head of the present invention. FIG. 4 is a graph diagram showing frequency characteristics, and FIG. 4 is a schematic diagram showing a specific application example of the embodiment of the present invention. FIG. 5 is a graph diagram showing another specific embodiment of the present invention. , FIG. 6 is a schematic diagram schematically representing another plan of the embodiment explained in FIG. 5, and FIG. 7 is a schematic diagram showing the principle of another embodiment of the present invention. The graph shown in FIG. 8 is a graph showing the properties of the magnetic films of the data signal recording layer and the servo signal recording layer of the medium to which the present invention is applied. 11... Data head gap loss characteristic curve, 12
... Servo head gap loss characteristic curve, 41...
・Servo head, 42...Data head, 43...
Recording medium, 44... Servo track, 45... Data track, 51... Servo head, 52... Data (15) Head, 53... Recording medium, 54... Servo track, 55... ... Data track, 71 ... Gap loss characteristic curve of data head, 72 ... Gap loss characteristic curve of servo head, 81 ... Characteristics of servo magnetic layer 82 ... Characteristics of data magnetic layer. (16) Z.Zu.

Claims (1)

[Claims] 1. In a data surface servo system used in an information recording device that records or reproduces a data signal on a data information signal recording layer on a recording medium using a conversion element, the conversion element is When positioning to a target data track based on a servo signal recorded on a recording medium, the servo signal is embedded servo information embedded in a lower layer of a data information signal recording layer on the recording medium. A data surface servo method in which data is recorded on a signal recording layer, and the recording frequency is higher than the recording frequency of the data signal. 2. A patent characterized in that the signals recorded in the data signal recording layer and the servo signal recording layer located below the data signal recording layer are reproduced using separate magnetic heads at frequencies corresponding to the mutual gap nulls. A data surface servo system according to claim 1. 3. The first gap null frequency of the magnetic head for reproducing the data signal is higher than the first gap null frequency of the magnetic head for reproducing the servo signal recorded on the servo layer disposed below the data signal recording layer. The data surface servo method according to claim 2, characterized in that the data surface servo method has a high value. 4. Claim 1, characterized in that the data signal recording layer is disposed in an area close to the surface of the recording medium, and the servo signal recording layer is disposed below the data signal recording layer.
The data surface servo method according to any one of items 1 to 3. 5. Claims characterized in that the recording layer for the data signal is disposed on a convex portion of the discrete track medium, and the recording layer for the servo signal is disposed in the groove portion of the discrete track medium, or in the entire layer including the groove portion. The data surface servo system according to any one of items 1 to 3. 6. A magnetic head for reproducing the data signal and a magnetic head for reproducing the servo signal are mounted on the same rigid body, according to any one of claims 2 to 5. Data surface servo method. 7. The data surface according to any one of claims 2 to 6, wherein the gap length of the magnetic head for reproducing the servo signal is larger than the gap length of the magnetic head for reproducing the data signal. Servo method. 8. At least one of the magnetic head for reproducing the data signal and the magnetic head for reproducing the servo signal is a perpendicular recording head.
The data surface servo method described in any of Item 6. 9. The reproducing signal of the servo signal and the reproducing signal of the data signal are each filtered at a frequency that is intermediate between the recording frequencies of both signals, according to any one of claims 1 to 8. Data surface servo method described in . 10. Any one of claims 1 to 9, characterized in that the coercive force of the magnetic layer on which the servo signal is recorded is larger than the coercive force of the magnetic layer on which the data signal is recorded. Data surface servo method described in .