JPH03189903A - Waveform correcting system - Google Patents

Abstract

PURPOSE:To improve a level margin with a phase margin also in case resolution is different between a product error and a recording medium by increasing and decreasing a synthetic signal with a delayed signal and the one with a signal passed through only a certain frequency band based on a fixed gain and making them correcting signals. CONSTITUTION:By a correcting signal in creased and decreased the signal of which the waveform of an analog data signal regenerated from a recording medium 2 by a head 1 is changed based on a fixed gain, the waveform of the analog data signal is corrected at a waveform correcting part 3. Here, a reference information recording part 4 in which reference information corresponding to a minimum frequency and a maximum frequency in the frequency band of the analog data signal is stored and a resolution operation part 5 which finds the amplitude of a reference signal regenerated from the reference information of the reference information recording part 4 by the head 1 and calculated the resolution to be the ratio of the amplitude of the reference signal corresponding to the maximum frequency corresponding to the amplitude of the reference signal corresponding to the minimum frequency are provided. Besides, a gain control part 6 to set the gain of the waveform correcting part 3 based on the found resolution is provided. Thus, a phase margin together with a level margin can be improved.

Description

Detailed Description of the Invention (Summary) The present invention increases or decreases a signal obtained by changing the waveform of an analog data signal reproduced from a recording medium by a head to create a correction signal based on a predetermined gain. Regarding the waveform correction method for correcting the waveform of the analog data signal in the correction section, the peak shift of the analog data signal reproduced for each recording medium is reduced to improve the phase margin, and the level margin is improved by removing noise. For the purpose of this, recording reference information corresponding to the minimum frequency and maximum frequency in the frequency band of the analog data signal reproduced by the head on the recording medium, and determining the amplitude of the reproduced reference signal from the reference information, The resolution is calculated based on this amplitude, and the gain of the waveform correction section is set based on this resolution.

[Industrial application field]

The present invention increases or decreases a signal obtained by changing the waveform of an analog data signal reproduced from a recording medium by a head to obtain a correction signal based on a predetermined gain, and uses this correction signal to adjust the waveform of the analog data signal in a waveform correction section. This invention relates to a waveform correction method.

In recent years, recording densities have been increasing in magnetic disk devices and the like, and there is a tendency for bit intervals on disks to become narrower.

For this reason, problems such as a decrease in the resolution of analog data signals occur due to effects such as peak shifts due to interference between waveforms. In magnetic disk drives, equalizers are effective and widely used as devices for correcting this.

[Prior Art] A conventional waveform correction method will be explained with reference to FIG. 6, taking an equalizer used in a magnetic disk drive as an example. In a conventional magnetic disk device, a head 11 reproduces data information written track by track on a magnetic disk as an analog data signal. This analog data signal is amplified by a signal amplifier (AMP) 12, and its waveform is slimmed by an equalizer 13 based on a preset delay amount and gain.
C) 14, the gain is controlled and outputted so that the output value is constant.

Then, noise is removed from this analog data signal through a low-pass filter (LPF), etc., and the peak point of each signal that reaches a set peak level in an analog-to-digital converter (hereinafter referred to as A/D converter) is detected. Detected A/
It had been converted to D.

[Problem to be solved by the invention]

By the way, in general, when the recording density of data information is increased by shortening the bit interval on a magnetic disk, that is, when the frequency of the reproduced signal is increased, the waveforms overlap due to the superposition of solitary waves as shown in Figure 7. Interference occurred, and the peak shift amount of the signal wave increased, and as shown in FIG. 8, the amplitude of the reproduced analog data signal gradually decreased, that is, the resolution decreased, making it difficult to detect the reproduced signal. Therefore, in order to prevent mutual interference of the waveforms of the solitary waves, the waveforms of the solitary waves are corrected by an equalizer. The resolution can generally be expressed as follows, where A is the lowest frequency and B is the highest frequency of the frequency band of the analog data signal reproduced by the head in FIG.

However, in the conventional waveform correction method, the waveform of the analog data signal reproduced by the head is corrected by an equalizer whose delay amount and gain are set to a constant value based on the resolution measured in advance.

For this reason, if there are multiple magnetic disks as recording media and there are product errors in the recording media, or if the recording density of data information is changed depending on the recording medium and the resolution differs between the recording media, the delay amount and gain can be kept constant. With conventional equalizers set to There was a problem with the recording medium.

Therefore, an object of the present invention is to provide a waveform correction method that can improve the phase margin by reducing the peak shift of an analog data signal reproduced for each recording medium, and can also improve the level margin by removing noise. purpose.

(Means for solving the problems) In the present invention, the means for solving the above problems are as follows:
As shown in FIG. 1, a signal obtained by changing the waveform of an analog data signal reproduced from a recording medium 2 by a head 1 is increased or decreased based on a predetermined gain to produce a correction signal, and this correction signal is used in a waveform correction section 3. In the waveform correction method for correcting the waveform of the analog data signal, reference information is recorded on the recording medium 2 that corresponds to the minimum frequency and maximum frequency among the frequency bands of the analog data signal reproduced by the head 1. The amplitude of the reference signal reproduced from the reference information in the reference information recording section 4 by the recording section 4 and the head 1 is determined, and is the ratio of the amplitude of the reference signal corresponding to the maximum frequency to the amplitude of the reference signal corresponding to the minimum frequency. This is because a resolution calculation section 5 that calculates the resolution and a gain control section 6 that sets the gain of the waveform correction section 3 based on the resolution determined by the resolution calculation section 5 are provided. Note that the predetermined gain refers to a gain that is set constant in advance.

[Effect]

The operation of the waveform correction method according to the present invention will be explained with reference to FIG.

First, the head 1 reproduces an analog data signal from the recording medium 2 . The waveform correction unit 3 generates a signal obtained by changing the waveform of this analog data signal, such as a composite signal of an analog data signal and a delayed signal such as this analog data signal, or a signal obtained by passing only a certain frequency band of the analog data signal. is increased or decreased based on a predetermined gain to obtain a correction signal, and the waveform of the analog data signal is corrected and output using this correction signal.

At that time, the head 1 reproduces the reference information corresponding to the minimum frequency and maximum frequency recorded in the reference information recording section 4 on the recording medium 2 as a reference signal, and the resolution calculation section 5 calculates the amplitude of each reference signal. Then, the resolution, which is the ratio of the amplitude of the reference signal corresponding to the maximum frequency to the amplitude of the reference signal corresponding to the minimum frequency, is calculated. Then, the gain control section 6 sets the gain of the waveform correction section 3 so that this resolution becomes optimal.

Therefore, the gain of the waveform correction section 3 is set by the gain control section 6 so that the resolution is optimized, and the waveform of the reproduced analog data signal can be corrected.

〔Example〕

Embodiments of the waveform correction method according to the present invention will be described below with reference to the drawings.

FIG. 2 is a diagram showing an example of a magnetic disk device employing the waveform correction method of this embodiment. In the figure, 21 is a head that reproduces an analog data signal from data information on a magnetic disk 20 that is a recording medium, 22 is a signal amplification unit (AMP) that amplifies the analog data signal reproduced by the head 21, and 23 is a signal An equalizer thins the waveform of the analog data signal passed through the amplification section 22, and an auto gain controller (AGC) 24 controls the gain to keep the reproduction of the analog data signal passed through the equalizer 23 constant.
It is. When the analog data signal normally passes through the AGC 24, noise is removed by a low-pass filter (not shown), the peak value is detected and digitized by the A/D converter (not shown), and the signal is sent to the data signal recognition unit (not shown). (not shown).

Further, in the case of this embodiment, the head 21 is located on the magnetic disk 20 at some of the locations where no data information is written between the tracks where data information is recorded.
A servo information area 20a in which servo information A and B are written for servo control of , and a reference information area 20b in which reference information 4F corresponding to the highest frequency is written, and the information in the two areas is read by the head 21 at the same time. Note that the servo information A and B are two-phase in order to distinguish between the inside and outside of the track.

Further, in FIG. 2, 25 detects two-phase servo signals A and B for servo control from the signals reproduced from the magnetic disk by the head 21, and based on these servo signals A and B, servo signal A is detected. This is a servo control section that controls the movement of the head 21, assuming that the head 21 is at the optimal position when the amplitudes of the signals B and B are equal.

Furthermore, 26 is the reference signal IF and 'o for detecting resolution from the signal reproduced from the magnetic disk by the head 21.
! 4F and calculates a resolution, which is a ratio of the amplitude of the reference signal IF to the amplitude of the reference signal 4F, from the reference signal IF and the amplitude of the 4F;
7 is a gain adjustment section 33 of the equalizer 23, which will be described later, so that, based on the resolution obtained by the resolution calculation section 26, the resolution approaches the optimum value whose characteristics have been determined in advance by measurement.
This is a gain control section that sets the gain of.

Further, the equalizer 23 of this embodiment has a configuration as shown in FIG. In the figure, the equalizer 23 has first and second equalizers that delay the input signal by a delay amount τ and output the delayed signal.
Delayline 31.3
2, the analog data signal reproduced from the head 21 and the analog data signal delayed by 2τ via the first delay line 31 and the second delay line 32, and the synthesized signal is gain controlled. A gain adjustment section 33 outputs the resultant attenuated based on the gain set by the section 27 by /2, and an analog data signal delayed by the delay amount and reproduced via the first delay line 31 is input as a positive input. A differential amplifying section 34 inputs the synthesized signal whose gain has been adjusted by a gain adjusting section 33 to a negative input terminal, and outputs the difference between the two.

Next, the operation of the waveform correction method according to this embodiment will be explained with reference to FIGS. 2 to 5.

First, in FIG. 2, before the head 21 reproduces an analog data signal from the data information on the magnetic disk 20, the servo information area 20a on the magnetic disk 2o is
At the same time, the reference information IF and 4F of the reference information area 20b are reproduced from the servo information A and B of the reference information area 20b.
The reference signals IF and 4F are reproduced from. These signals are input to the servo control unit 25 and resolution calculation unit 26 via the AMP 22, equalizer 23, and AGC 24. Also, these signals are processed by AGC in the same way as analog data signals.
24, and reaches the data signal recognition section via the low-pass filter and the A/D conversion section, but is not detected there.

Then, the servo control unit 25 detects servo signals A and B for servo control from the signals reproduced by the head 21 from the magnetic disk 20, and based on the amplitudes of the servo signals A and B, the servo signals A and B are used for servo control. The position of the head 21 is adjusted so that the amplitudes of B are equal.

At the same time, the resolution calculation section 26 uses the reference signals IF and 4F for resolution detection from the signal reproduced by the head 21.
is detected, and the resolution, which is the ratio of the amplitude of the reference signal IF to the amplitude of the reference signal 4F, is calculated from the amplitudes of the reference signals IF and 4F. Then, the gain control section 27
Based on this resolution, sends a gain adjustment signal to the gain adjustment section 33 of the equalizer 23 and sets the gain to /2 so that the resolution approaches the optimum value determined in advance by measurement or the like.

Then, if an analog data signal (this signal is expressed by a time function f(t)) as shown in FIG. 4(a) is reproduced from the data information on the magnetic disk 20 by the disk 21, This analog data signal is AMP
22 to the equalizer 23, where the gain is set so that the resolution approaches the optimum value.
The waveform is corrected by

That is, in FIG. 3, the analog data signal input to the equalizer 23 is first delayed by the amount of delay by the first delay line 31, and then becomes the delayed signal (f (with -) shown in FIG. 4(b)). ). A part of this delayed signal is input to the positive input terminal of the differential amplifier 34, while the other is delayed by the delay amount again by the second delay line 32, and the delayed signal shown in FIG. 4(C) ( f (at t-2)). Then, this delayed signal (f(t-2τ)) and the original analog data signal (f(t)) are synthesized as shown in FIG. 4(d), and the synthesized signal shown in FIG. 4(e) is (f (
t)+f (at t-2)) and is input to the gain adjustment section 33. Therefore, this composite signal is attenuated based on a gain of /2 so that the resolution approaches a predetermined optimal value, and the correction signal (k/2) shown in FIG.
2 (f(t)+f(at t-2))), and is input to the negative input terminal of the differential amplifier 34. In the differential amplification section 34, the delayed signal (f(t-τ)) shown in FIG.
The above correction signal (k/2 (f(t)+f
(at t-2)))), and convert the difference to the analog data signal (f(-τ)-/2 (f()) after waveform correction.
t)+f(at t-2))). For this reason,
The analog data signal reproduced by the head 21 is corrected by the equalizer 23 in which the gain of the gain adjustment section 33 is set to /2 so that the resolution approaches the optimum value, and as shown in FIG. 5, mutual interference of solitary waves is eliminated. This also reduces the peak shift of the analog data signal.

Therefore, according to this embodiment, the analog data signal reproduced from the data information on the magnetic disk 20 by the head 21 is input to the equalizer 23 via the AMP 22,
Therefore, the waveform is corrected based on the gain of the gain adjustment section 33 set to /2 so that the resolution obtained by the resolution calculation section 26 approaches the optimal value obtained by measurement or the like in advance.

For this reason, the influence of mutual interference of solitary waves is reduced, and the resolution of the analog data signal reproduced for each recording medium approaches the optimal value, which improves the level margin for each recording medium, reduces peak shift, and improves the phase margin. improves.

As a result, it is possible to reduce the probability that an error will occur when converting the data signal into a signal.

At the same time, the servo control unit 25 detects the servo signals A and B and performs servo control of the head, readjusts any deviations in the head position, and moves the head to the optimal position, so that the analog data signal is more reliably transmitted. The error rate when recognizing can be reduced.

In this embodiment, the number of heads is 1 and the number of magnetic disks corresponding to the head is 1. However, this is for convenience; for example, if a plurality of heads are provided corresponding to the number of magnetic disks, the gain can be The gain control by the control section may be performed on a plurality of equalizers, or may be performed by sequentially switching the equalizers. Further, in this embodiment, a delay line is provided in the equalizer for explanation, but since it is sufficient to create a signal with a waveform different from that of the reproduced signal, in the present invention, a filter (for example, a BPF) can be used instead of a delay line. ) etc. may be provided. Furthermore, in this embodiment, the head 21
Although a number of servo controls and equalizer gain controls were performed before reproducing analog data signals from data information on a magnetic disk, there is no problem in reproducing data signals and controlling them at the same time. .

〔Effect of the invention〕

As explained above, according to the present invention, the head reproduces the reference signal from the reference information in the reference information recording section, and the resolution calculation section calculates the resolution from the amplitude value of this reference signal. The gain control unit sets the gain of the waveform correction unit so as to approach the optimum value determined by . For this reason, the influence of mutual interference of solitary waves is reduced, and the resolution of the analog data signal reproduced for each recording medium approaches the optimal value, which improves the level margin for each recording medium, reduces peak shift, and improves the phase margin. improves. As a result, the probability of errors occurring when reading data signals can be reduced.

[Brief Description of the Drawings] Fig. 1 is a diagram showing the principle of the present invention, Fig. 2 is a diagram showing an example of a magnetic disk device adopting the waveform correction method of this embodiment, and Fig. 3 is a diagram showing an example of a magnetic disk device adopting the waveform correction method of the present embodiment.
Figure 4 shows an example of the equalizer according to this embodiment.
The figures show the action of the equalizer according to the present embodiment, Fig. 5 shows the waveform of the data signal improved by the present embodiment, Fig. 6 shows the conventional example, and Fig. 7 shows the conventional example. FIG. 8 is a diagram showing the mutual interference of solitary waves, and FIG. 8 is a diagram showing the frequency characteristics of the amplitude of the signal reproduced by the conventional example. 1.21... Head 2.20... Recording medium (magnetic disk) 3.23...
- Waveform correction section (equalizer) 4.20b... Reference information recording section (reference information area) 5.26... Resolution calculation section 6.27... Gain control section

Claims (1)

[Claims] A signal obtained by changing the waveform of an analog data signal reproduced from a recording medium (2) by a head (1) is increased or decreased based on a predetermined gain to obtain a correction signal, and the waveform correction unit uses this correction signal. In the waveform correction method of correcting the waveform of the analog data signal in (3), it corresponds to the minimum frequency and maximum frequency among the frequency bands of the analog data signal reproduced by the head (1) on the recording medium (2). The amplitude of the reference signal reproduced by the head (1) from the reference information of the reference information recording part (4) is determined, and the amplitude of the reference signal corresponding to the minimum frequency is determined. A resolution calculation unit (
5); and a gain control section (6) that sets the gain of the waveform correction section (3) based on the resolution determined by the resolution calculation section (5).