JPH05197910A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To effectively equalize it further by changing the equalization characteristic of a waveform equalization circuit according to the characteristic of a reading waveform. CONSTITUTION:The waveform read by magnetic heads 52, 53 is supplied to a changeover switch circuit 15, and the changeover switch circuits 11-15 are switched in accordance with a head selection signal 55 generated by a controller 54. For example, when an inner peripheral head 52 is selected, the circuit 15 is connected to a terminal (b) side and the reading waveform of the head 52 is selected, and the circuits 11-14 are connected to the terminals (a) and the delay line 21 of a delay time to and the attenuator 31 of art attenuation rate k1 are selected. On the other hand, when an outer peripheral head 53 is selected, the circuit 15 is connected to the terminal (a) side and the reading waveform of the head 53 is selected, and the circuits 11-14 are connected to the terminals (b) side and the delay line 22 of the delay time tau2 and the attenuator 32 of the attenuation rate k2 are selected. Then, the affection due to the difference of the reading waveform characteristics in the inner peripheral head and the outer peripheral head is reduced and higher recording density is attained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waveform equalizing circuit for processing a head read waveform of a magnetic recording device and equivalently improving recording / reproducing characteristics.

[0002]

2. Description of the Related Art In magnetic recording devices such as magnetic disk devices, the capacity and the recording density have been increased year by year. To achieve the high recording density, the bit density and the track density have to be improved. It's peeled off. Achieving higher bit densities mainly depends on improving the performance of magnetic heads and magnetic recording media, and shortening the spacing between magnetic heads and media.

However, since it is becoming difficult to improve these heads, media, etc., recently, a method of equivalently improving the recording / reproducing characteristics by processing the waveform read by the head by a reproducing circuit is used. Is becoming.

As one of the techniques, there is known a waveform equalizing circuit including a combination of a delay line 4, an attenuator 5 and a differential amplifier 3 as shown in FIG. This waveform equalizer circuit has a read input waveform 1 as shown in FIG. 2 for an isolated inverted waveform.
By removing the skirt portion (illustrated by the solid line) and making it fine, and obtaining an output 2 (illustrated by the dotted line) with a small waveform spread, it is obtained as a superposition of isolated inverted waveforms as shown in FIG. The reproduction frequency characteristic is improved from the curve 6 shown by the solid line to the curve 7 shown by the dotted line to reduce the pattern peak shift. This pattern peak shift is mainly caused by intersymbol interference of the read waveform, and the finer and sharper the waveform, the smaller the pattern peak shift.

[0005]

By the way, in a magnetic recording apparatus for recording / reproducing using a plurality of magnetic heads,
Inevitably, the characteristics of each magnetic head vary. Also,
When using a plurality of magnetic disks, there are variations in the characteristics of the medium. Further, in the magnetic disk device, the waveform characteristics (particularly the thickness) are different due to the difference between the recording / reproducing positions (for example, inner circumference and outer circumference) on the magnetic disk surface. Therefore, the magnitude of the pattern peak shift of the waveform varies depending on the situation,
It has always been difficult to obtain good recording and reproducing characteristics.

That is, in the conventional equalization circuit, since the equalization characteristics, for example, the circuit constants of the delay time and the attenuation rate are fixed, the equalization effect, that is, the reduction amount of the pattern peak shift becomes constant, and the equalization degree There will be excess or deficiency.

The present invention provides a waveform equalization circuit which eliminates the above-mentioned drawbacks, reduces the influence on the pattern peak shift due to the difference in characteristics of read waveforms, and can stably obtain good recording and reproducing characteristics. The purpose is to

[0008]

In order to achieve the above object, a magnetic disk device of the present invention comprises a disk-shaped information recording medium and a first magnetic disk for reproducing the inner peripheral side of the disk-shaped information recording medium. A head, a second magnetic head for reproducing the outer peripheral side of the disk-shaped information recording medium, and a switch for switching the first magnetic head and the second magnetic head to reproduce an information signal from the disk-shaped information recording medium. Means, a waveform equalization circuit for performing waveform equalization processing on the reproduced information signal, and a waveform equalization circuit based on which of the first magnetic head and the second magnetic head is reproducing the information signal. It is characterized by having a means for changing the equalization characteristic.

[0009]

According to the present invention, in a magnetic disk device in which a plurality of heads separately reproduce the inner and outer circumference sides of the disk, the difference in characteristics between magnetic heads and the reproduction signal characteristics of the inner and outer circumferences of the magnetic disk. It is possible to easily change the waveform equalization characteristic by adapting to the difference between

Conventionally, for example, Japanese Patent Application Laid-Open No. 55-34304 discloses a technique of changing the equalization characteristic according to a track position signal from a servo head. According to the present invention, a plurality of heads are used. Assuming that high-speed access is possible by recording and reproducing the inner and outer circumferences of the magnetic disk in a shared manner, the difference in characteristics between the magnetic heads and the difference in reproduction signal characteristics between the inner and outer circumferences of the medium are By switching the equalization characteristics for each head, the excess and deficiency of the equalization can be reduced at the same time with a simple structure, and more effective equalization can be performed.

[0011]

The present invention will be described below.

First, FIG. 4 shows how the pattern peak shift changes when the delay time τ and the attenuation rate K are changed in the equalizer circuit of FIG. As is apparent from FIG. 4, changing the delay time τ and the attenuation rate K changes the pattern peak shift. Therefore, when the characteristics of the read waveform are different and the magnitude of the pattern peak shift is different, it is understood that different delay times τ and attenuation rates K may be used.

The present invention is characterized in that effective equalization suitable for the head read waveform can be performed by switching the delay time τ and the attenuation rate K while using the same reproducing circuit.

FIG. 5 shows a circuit configuration of an embodiment of the present invention. One ends of the two delay lines 21 and 22 are respectively connected to terminals a and b of the changeover switch circuit 13, the changeover switch circuit 13 is connected to the plus terminal of the differential amplifier 40, and the delay lines 21 and 22 are mutually connected. Different delay times τ ₁ , τ ₂
Have. One ends of the two attenuators 31 and 32 are connected to terminals a and b of the changeover switch circuit 14, respectively, and the changeover switch circuit 14 is connected to the negative terminal of the differential amplifier 40. Different attenuation rate K
₁ and K ₂ . The other ends of the delay lines 21 and 22 are connected to the terminals a and b of the changeover switch circuit 11, and the attenuators 31 and 32 are connected.
The other end of is connected to the terminals a and b of the changeover switch circuit 12, and the changeover switch circuits 11 and 12 are commonly connected to the changeover switch circuit 15. According to such a configuration, the delay time τ and the attenuation rate K can be switched by switching the changeover switch circuits 11 to 14 by the control signal, and the equalization suitable for the read waveform can be performed.

What is important in carrying out the present invention is that
What kind of signal is used as the control signal. As one of such control signals, when applied to a magnetic disk device, a head selection signal indicating which of the inner head and the outer head is used for reading can be used.

In an ordinary magnetic disk device, FIG.
As shown in FIG. 3, from the viewpoint of speedup, the magnetic heads 52,
53, the time required for the magnetic head to seek the target track can be shortened.
Since the head selection signal for selecting which head is generated by the controller 54 of the magnetic disk device, this head selection signal 55 may be used as the control signal of the changeover switch circuit.

That is, the waveform read by the magnetic heads 52 and 53 is supplied to the changeover switch circuit 15, and the changeover switches 11 to 15 are changed over according to the head selection signal 55 generated by the controller 54. For example, when the inner circumference head 52 is selected, the changeover switch circuit 15 is connected to the terminal b side, the read waveform of the inner circumference head 52 is selected, and the changeover switch circuits 11 to 14 are connected to the terminal a side. Connected to a delay line 21 having a delay time τ ₁ and an attenuator 31 having an attenuation rate K _1.
Select. On the other hand, when the outer peripheral head 53 is selected, the changeover switch circuit 15 is connected to the terminal a side, the read waveform of the outer peripheral head 53 is selected, and the changeover switch circuits 11 to 14 are connected to the terminal b side. Delay time τ ₂
The delay line 22 and the attenuator 32 having the attenuation factor K ₂ are selected.

Therefore, by properly setting the delay time τ of each delay line and the attenuation rate K of each attenuator, waveform equalization suitable for the read waveforms of the inner peripheral head and the outer peripheral head can be performed, Therefore, it is possible to reduce the influence of the difference in the read waveform characteristics between the inner head and the outer head, and it is possible to achieve higher recording density.

According to the experiments conducted by the present inventor, τ ₁ = 35 ns and K ₁ = 0.2 for the inner circumference head, and τ ₂ = 30 ns and K ₂ = 0.1 for the outer circumference head. The output waveform was obtained. In the magnetic disk device, the magnitude of the pattern peak shift is considerably different between the inner circumference and the outer circumference, and the effect is extremely large even if only two kinds of delay time and attenuation rate are switched.
In the above embodiment, both the delay time and the attenuation rate are switched, but it goes without saying that only one of them may be switched.

As the control signal for switching,
Not only the head selection signal but also the read signal itself can be used. For example, the goodness of the frequency characteristic, the resolution, the half-value width of the isolated inverted waveform, and the like are measured and calculated, and the result is classified into several types to be used as the control signal.

Next, an embodiment of the present invention using such a control signal will be described. FIG. 6 shows a circuit configuration of another embodiment of the present invention, in which the equalization characteristic is switched according to the output resolution. 6, the same or equivalent components as those of the circuit of FIG. 5 are designated by the same reference numerals. Information is recorded in advance on the tracks on the magnetic disk 51 by recording signals D ₁ and D ₂ of two kinds of frequencies [maximum recording frequency (for example, 8 MHz) and half frequency (for example, 4 MHz)] at predetermined positions. When reproducing, these two types of signals D ₁ and D ₂ are controlled so as to be read first, and the reproduction output corresponding to these signals D ₁ and D ₂ is converted from the reproduction signal of the head into the A / D converter 56. Then, the value is sampled and digitized, and the value of output resolution = reproduction output (maximum recording frequency) / reproduction output (half the frequency) is calculated by the divider 57. The output of the divider 57 is compared with a predetermined set value (for example, 0.9) by the comparator 58. If it is equal to or larger than the set value, "0" is output, and if it is less than the set value, "1" is output. The output 59 of the comparator 58 is used as a control signal for switching, and the switch circuits 11 to 14 are switched according to this control signal. The changeover switch circuit 15 is changed over by the head selection signal 55 as in the embodiment of FIG. In the present embodiment, for example, when the set value of the comparator 58 is 0.9 and the control signal is "1", that is, the output resolution is <0.9, τ ₁ = 35 ns and K ₁ = 0.2 are set, and the control signal is Is 0, that is, when the output resolution is ≧ 0.9, by setting τ ₂ = 30 ns and K ₂ = 0.1, a good output waveform with a small variation in the pattern peak shift was obtained.

As described above, according to this embodiment, by properly setting the delay time τ of each delay line and the attenuation rate K of each attenuator, the characteristics of the read waveform are changed and the output resolution is improved. Even if there is a change, optimum waveform equalization can be performed accordingly, and the influence of fluctuations and variations in the read waveform can be reduced.

In the above description, only the case where the delay time and the value of the attenuation rate are switched in two steps has been described, but the present invention is not limited to this, and for example, the setting for comparison by the comparator 58 is set. It is also possible to set the value to two or more and to set the control signal, the attenuator, the delay line, and the switching terminal of the changeover switch circuit to three or more to switch in three or more steps.

Further, in FIGS. 5 and 6, two attenuators 3 are used.
Although 1 and 32 are switched by using the two changeover switch circuits 12 and 14 connected to both ends thereof, it is also possible to connect the changeover switch circuit to only one side by using the configuration shown in FIG.

[0025]

As described above, according to the present invention, the equalization characteristics can be switched according to the characteristics of the read waveform, so that it is possible to reduce the influence on the pattern peak shift due to fluctuations and variations in the read waveform. , The effectiveness of the equalization circuit can be significantly improved.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a conventional equalization circuit.

FIG. 2 is a diagram showing input / output waveforms of the circuit of FIG.

FIG. 3 is a diagram showing frequency characteristics for explaining the effect of the equalization circuit.

FIG. 4 is a diagram showing a relationship between a delay time and an attenuation rate and a pattern peak shift.

FIG. 5 is a diagram showing an embodiment of the present invention.

FIG. 6 is a diagram showing an example of the present invention.

FIG. 7 is a diagram showing an example of an attenuator used in the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kayoshi Nakabayashi 2880 Kokuzu, Odawara-shi, Kanagawa Hitachi Ltd. Odawara factory (72) Inventor Takamasa Uchiyama 2880, Kozu, Odawara, Kanagawa Hitachi Ltd. Odawara factory

Claims (5)

[Claims] 1. A disc-shaped information recording medium, a first magnetic head for reproducing the inner peripheral side of the disc-shaped information recording medium, and a second magnetic head for reproducing the outer peripheral side of the disc-shaped information recording medium. Magnetic head, switching means for reproducing the information signal from the disk-shaped information recording medium by switching the first magnetic head and the second magnetic head, and a waveform for performing waveform equalization processing on the reproduced information signal. A magnetic disk device having an equalizing circuit and a control means for changing the equalizing characteristic of the waveform equalizing circuit based on which of the first magnetic head and the second magnetic head is reproducing the information signal. 2. The equalization circuit includes means for branching an information signal from the magnetic head, delay means for delaying one branched information signal, and attenuation for attenuating the other branched information signal. 2. The magnetic disk device according to claim 1, further comprising: a means, and a differential amplifier that receives the information signal delayed by the delay means and the information signal attenuated by the attenuator. 3. The magnetic disk drive according to claim 2, wherein both the delay amount and the attenuation amount are variable. 4. The delay means comprises a plurality of delay lines,
4. The magnetic disk device according to claim 2, wherein the delay amount is variable by switching the plurality of delay lines. 5. The control means has a control means for changing the equalization characteristic of the waveform equalization circuit based on a head selection signal for selecting a magnetic head to be reproduced.
The magnetic disk device according to any one of 1.