JPH05197909A - Recording device and waveform equalizer - Google Patents

Abstract

PURPOSE:To minimize excess and deficiency of equalizing caused by dispersion of characteristics of magnetic head, dispersion of medium and dispersion of signals at recording by switching an equalizing characteristics according to resolution of reproduced signals. CONSTITUTION:Signal waveform read out from the magnetic head 52 and 53 is supplied to the changeover switch circuit 15, and the changeover switch 11-15 are switched according to the head selecting signal 55 generated in the controller 54. For instance, when the inner peripheral head 52 is selected, the changeover switch circuit 15 is connected to the terminal (b) side, signal waveform read out from the inner peripheral head 52 is selected, the changeover switch circuits 11-14 are connected to the terminal (a) side, and the delay line 21 of delay time tau1 and the attenuator 31 of attenuation factor k1 are selected. On the other hand, when the outer peripheral head 53 is selected, the circuit 15 is connected to the terminal (a) side, signal waveform read out from the outer peripheral head 53 is selected, the changeover switch circuits 11-14 are connected to the terminal (b) side, and the delay line 22 of delay time tau2 and the attenuator 32 of attenuation factor k2 are selected.

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 the head and the 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.

Conventionally, for example, Japanese Patent Laid-Open No. 55-3430.
Japanese Patent No. 4 discloses a technique of changing the equalization characteristic according to the track position.

[0006]

However, in the technique disclosed in, for example, Japanese Patent Laid-Open No. 55-34304, there are variations in characteristics among magnetic heads in a magnetic recording device that uses a plurality of magnetic heads for recording and reproduction, and a plurality of magnetic heads. It was not possible to deal with variations in the characteristics of the medium when using a magnetic disk.

That is, in a magnetic recording apparatus that records and reproduces data by using a plurality of magnetic heads to realize high-speed access, variations in characteristics cannot be avoided from one magnetic head to another. Further, when a plurality of magnetic disks are used to increase the capacity, 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, and it has been difficult to always obtain good recording and reproducing characteristics.

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

[0009]

To achieve the above object, circuit constants such as a delay time and an attenuation factor are switched according to the characteristics of a read waveform.

That is, the present invention comprises a recording medium, a head for reproducing a reproduced signal from the recording medium, an equalizing circuit which is composed of a delay means and an attenuating means, and which equalizes the reproduced signal.
It is characterized in that it has means for varying at least one of the delay amount of the delay means and the attenuation amount of the attenuating means based on the resolution of the reproduction signal from the head.

According to another aspect of the present invention, a head is selected from a plurality of heads, a reproduction signal is reproduced from a recording medium by the selected head, and an isolated inverted waveform of the reproduction signal from the selected head is displayed. In a signal reproducing method for performing a waveform equalization process in which a skirt portion is removed to thin the waveform, the equalization characteristic of the waveform equalization process is changed based on the resolution of the reproduction signal of the selected head.

Further, according to another aspect of the present invention, a plurality of delay lines having different delay times and one of the plurality of delay lines are provided.
A first switch means for selecting one, a plurality of attenuators having different attenuation factors, a second switch means for selecting one of the plurality of attenuators, and a first switch means. A differential amplifier that receives as input the signal that has passed through the delay line and the signal that has passed through the attenuator selected by the second switch means. It is characterized in that the operation of the first and second switch means is controlled.

[0013]

According to the present invention, by changing the equalization characteristic according to the resolution of the reproduction signal, the characteristic variation of the magnetic head,
It is intended to reduce excess or deficiency of equalization due to variations in media, variations in signals during recording, etc., and perform more effective equalization.

[0014]

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 a normal 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 waveforms read by the magnetic heads 52 and 53 are 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 head and the outer head can be performed, Therefore, it is possible to reduce the influence of the difference in read waveform characteristics between the inner head and the outer head, and it is possible to achieve higher recording density.

According to the experiments 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, 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.

[0027]

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.

Front page continuation (72) Inventor Kazuyoshi Nakabayashi 2880 Kokuzu, Odawara, Kanagawa Prefecture Hitachi Ltd. Odawara Plant (72) Inventor Takamasa Uchiyama 2880, Kozu, Odawara Kanagawa Ltd.

Claims (8)

[Claims] 1. A recording medium, a head for reproducing a reproduced signal from the recording medium, an equalizing circuit for equalizing the reproduced signal, which is composed of a delay means and an attenuating means, and a reproduced signal from the head. A recording apparatus comprising means for varying at least one of the delay amount of the delay means and the attenuation amount of the attenuation means based on the resolution. 2. The equalizing circuit branches the reproduced signal from the head, delay means for delaying one branched reproduced signal, and attenuating means for attenuating the other branched reproduced signal. 2. The recording apparatus according to claim 1, further comprising: a reproduction signal delayed by the delay means and a differential amplifier which receives the reproduction signal attenuated by the attenuating means as inputs. 3. The recording apparatus according to claim 1, wherein both the delay amount and the attenuation amount are variable. 4. A signal indicating the resolution is generated by means for calculating the resolution of a reproduced signal reproduced by the head and means for comparing the output of the means with a predetermined set value. The recording apparatus according to any one of 1 to 3. 5. A head is selected from a plurality of heads, a reproduction signal is reproduced from a recording medium by the selected head, and a skirt portion of an isolated inverted waveform of the reproduction signal from the selected head is removed to make the head thinner. In the signal reproduction method for performing the waveform equalization process, the equalization characteristic of the waveform equalization process is changed based on the resolution of the reproduction signal of the selected head. 6. A plurality of delay lines having different delay times, a first switch means for selecting one of the plurality of delay lines, a plurality of attenuators having different attenuation factors, and the plurality of attenuators. Second switch means for selecting one of the attenuators;
A differential amplifier which receives as an input the signal that has passed through the delay line selected by the first switch means and the signal that has passed through the attenuator selected by the second switch means. A waveform equalizing circuit, characterized in that the operations of the first and second switch means are controlled according to the characteristics of the input waveform supplied to the container. 7. The waveform equalizing circuit according to claim 6, further comprising an extracting unit for extracting a control signal for controlling the operation of the first and second switch units from the input waveform. 8. The waveform equalization according to claim 7, wherein the extraction means has means for calculating the resolution of the input waveform and means for comparing the output of the means with a predetermined set value. circuit.