JP3086056B2 - Magnetic recording / reproducing apparatus and reproducing signal processing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reproducing signal processing technique for a magnetic recording / reproducing apparatus, and more particularly to a reproducing apparatus suitable for use in an IC including automatic response equalization and partial response waveform processing, and a method for processing the reproduced signal.

[0002]

2. Description of the Related Art A signal transmission technique of a partial response (hereinafter abbreviated as PR), which has been taken up in the communication field, has been applied to a recording / reproducing technique of a magnetic disk drive. This relates to a band narrowing technique for converting one piece of information into a plurality of sample values.Using this technique for magnetic recording, the band of a recording signal is compressed and recorded, and a narrow band signal is converted to a plurality of signals. It is identified by a threshold value. Conventionally, the PR waveform processing has been realized by a fixed equalizer as disclosed in Japanese Patent Application Laid-Open No. 2-150114. FIG. 7 shows a reproduction signal processing circuit to which this conventional circuit is applied. This circuit performs equalization corresponding to PR waveform processing in a fixed stage 8 prior to the digital automatic equalizer 12 ′, and then detects a change in the characteristics of the electromagnetic conversion system due to a change in track position or the like.
The characteristics of the circuit and the equalizer 12 'are automatically set so as to be absorbed and decoded by the discriminator 13 comprising a Viterbi decoder. That is, the automatic equalizer 12 'does not include the function of the PR waveform processing. By applying such automatic equalization, the freedom of circuit design can be expanded,
As a result, the cost of the apparatus can be reduced.
However, the fixed equalizer 8 that performs equalization equivalent to the PR waveform processing requires complicated characteristics including slimming of a waveform, a notch at a specific frequency, and noise removal. Is an operational amplifier, a large-capacity capacitor,
Components such as inductance are indispensable, and it is extremely difficult to make an IC including these components.

[0003]

As described above, in the prior art, it cannot be said that sufficient consideration is given from the viewpoints of simplification of a circuit and integration of an IC, and there is a problem that the integration of an IC is particularly difficult. Was. SUMMARY OF THE INVENTION It is an object of the present invention to provide a magnetic recording / reproducing apparatus and a reproduction signal processing method which can simplify the circuit in the signal processing including the PR waveform processing and can be easily integrated into an IC.

[0004]

In order to achieve the above object, a magnetic recording / reproducing apparatus according to the present invention uses a specific recording pattern for setting the characteristics of an automatic equalizer 12 as shown in FIG. A memory 16 for recording, a pattern converter 15 for converting a recording pattern in the memory into an equalization target pattern corresponding to an equalized waveform after PR waveform processing, and an automatic equalization target pattern output from the pattern converter. An equalization error calculation means for calculating an output error of the equalizer and controlling constant setting of the automatic equalizer so as to reduce the error;
Equalizing means corresponding to the waveform processing of the PR is added to the reproduction signal processing circuit 3, and the circuit configuration of the automatic equalizer includes the P
It is configured to include equalization corresponding to the waveform processing of R. That is, the automatic equalizer according to the present invention has a configuration including not only the conventional equalization operation that follows characteristic fluctuations and the like during operation of the device but also the equalization operation corresponding to the above-described PR waveform processing. The basic feature is that the configuration of the fixed equalizer is unnecessary. Here, as shown in FIG. 2, for example, an A / D conversion circuit 11 is provided between the automatic equalizer 12 and the discriminator at a stage subsequent to the automatic equalizer 12, and a discriminator having a digital configuration for discriminating reproduced data using a digital signal is provided. In this case, a high-performance discriminator that handles digital signals can be applied, which is preferable.
Alternatively, in this case, as shown in FIG. 3, for example, a simple discriminator 17 that outputs a discrimination result for each bit is provided at the output of the automatic equalizer 12, and when reproducing data, the output of the simple discriminator 17 is set to the equalization target. Used to calculate the equalization error as a pattern,
If the characteristics of the automatic equalizer are sequentially corrected, the identification function can be followed more quickly.

Alternatively, for example, as shown in FIG. 4, if an A / D conversion circuit 11 is provided in a stage preceding the automatic equalizer 12, and an automatic equalizer using digital signals is provided, Can be digitized, and miniaturization becomes easy. Alternatively, as shown in FIG. 5, for example, a constant memory 18 is further provided connected to the automatic equalizer 12, and an equalization constant of the automatic equalizer 12 is set by a memory constant recorded in the constant memory 18, Alternatively, as a means for updating the contents of the constant memory 18 by updating the equalization constant of the automatic equalizer 12, for example, a means such as a group of counters 23 holding constants in FIG. In this case, the advantage of the effective and diversified use of the memory arises as much as the memory for setting the constant is added, or the equalization constant can be easily updated in response to the temporal change of the magnetic recording / reproducing system. There are advantages. Here, since the number of taps of the automatic equalizer includes the PR waveform processing, the constants near the center tap become equal. Therefore, it is preferable to set the number to an even number, and it is preferable because equalization with high accuracy can be easily obtained. By integrating the reproduction signal processing circuit with the circuit configuration of the automatic equalizer including the equalization means corresponding to the above-mentioned PR waveform processing, not only these signal processing circuits but also the magnetic recording and reproducing apparatus can be miniaturized. Cost is also reduced.

Alternatively, in order to achieve the above object, according to the present invention, in a reproduction signal processing method of a magnetic recording / reproducing apparatus, equalization processing equivalent to PR waveform processing is included in one automatic equalization processing. It will be performed as follows. (1) The automatic equalizer performs PR so that the equalization error is reduced.
The equalization characteristics are corrected including the characteristics of the waveform processing described above. Identifying the corrected equalized output by the classifier to obtain a reproduced data output,
(2) The equalization error is obtained by subtracting the pattern value to be the equalization target from the output value of the automatic equalizer. (3) The pattern value to be the equalization target is, for example, after the PR waveform processing at the time of initial setting. The pattern value corresponding to the equalized waveform is selected, and the output of the discriminator is selected during the subsequent adaptive operation. (4) The pattern value corresponding to the equalized waveform after the PR waveform processing is the characteristic of the automatic equalizer Is recorded in the memory, and the recording pattern in the memory is converted and obtained. In the reproduction signal processing method in this case, if the setting of the equalization constant is performed as follows using the constant memory connected to the automatic equalizer, the present invention using the constant memory It is preferable as a reproduction signal processing method having an advantage corresponding to the above device configuration. That is, (1) a constant of an automatic equalizer is obtained while reproducing information recorded in a known pattern, and recorded in a constant memory. When reproducing data, the constant memory is read out and reset as an equalization constant. I do. According to this method, it is not necessary to store information recorded in a known pattern in the memory data of the automatic equalizing means after the initial setting, and the information can be effectively used in a user data memory or the like. Alternatively, (2) the equalization constant reset with the contents of the constant memory is updated while reproducing data, and the contents of the constant memory are rewritten at the end of the reproduction operation. This method makes it easy to respond to updates with time-dependent fluctuations and the like.

[0007]

The present invention focuses on the fact that the PR waveform processing is linear processing, and automatically equalizes the reproduction signal from the magnetic head, including the PR waveform processing. That is,
After performing the equalization corresponding to the PR waveform processing in the initial setting, the equalization processing may be performed by following the characteristic fluctuation at the time of the adaptive operation. Therefore, in the present invention, the equalization processing is performed by one automatic equalizer. Included in the configuration. In this configuration, as the equalizing means corresponding to the PR waveform processing, in particular, a memory for recording a specific recording pattern, for example, 16 in FIG. 1, and a pattern for converting a recording pattern of the memory to an equalization target pattern It is necessary to add a converter 15 and an equalization error calculator 4 for calculating the output error of the automatic equalizer based on the output of the equalization target pattern and controlling the constant setting of the automatic equalizer, etc. to the reproduction signal processing circuit. is there. The memory and PR pattern converter that constitute the main part do not include complicated elements such as problems of the electromagnetic conversion system due to the fluctuation of the track position on the recording medium, and simply perform pattern conversion from memory data. As it is, its construction does not require complexity. That is, a digital memory is used as the memory, and the memory can be constituted by an adder of about 2 bits at the maximum. On the other hand, in the present invention, instead of adding such a simple component, a conventional fixed equalizer is not necessary, and therefore, the slimming of a waveform or a specific frequency required for a conventional fixed equalizer is not required. This eliminates the need for a notch, an operational amplifier for removing noise, a large-capacity capacitor, an inductance, and the like. As described above, according to the present invention, the circuit configuration is basically simplified, the IC can be implemented, and the cost is reduced.

In the present invention, digitization by using an A / D converter further simplifies the circuit and makes it more advantageous to use an IC, and further enhances the performance by using a maximum likelihood decoder described later. Also becomes possible. In this case, the adaptation speed can be improved by employing the simple classifier of the present invention.

According to the present invention, the memory for setting and updating the equalization constant of the automatic equalizer is provided separately from the memory for storing the specific pattern for the initial setting. The preset operation to be performed is performed offline and recorded in the constant memory, and when reproducing the data, by resetting the equalization constant determined offline,
Preset data recorded in advance for initial setting can be deleted after obtaining the equalization constant, and user data can be recorded in this part as well. Effective and diversified memory Bring use.

When the automatic equalizer including the PR waveform processing of the present invention is realized by a transversal type equalizer, the tap constants of the equalizer become almost equal in the vicinity of the center tap. Regardless of the analog configuration or the digital configuration, the number of taps is set to an even number, thereby easily realizing highly accurate equalization.

[0011]

FIG. 1 shows an embodiment of the present invention. A preamplifier 7 for amplifying a reproduction signal from the head 2, an AGC circuit 9,
A reproduction signal processing circuit 3 including a PF 10, an identifier 13, an automatic equalizer 12 for automatically changing characteristics so as to reduce an equalization error, and a specific recording pattern for initializing the characteristics of the equalizer. , A PR pattern converter 15 for converting a preset pattern into a pattern corresponding to an equalized waveform after the PR waveform processing, and a pattern switching for selecting a preset pattern only at the initial setting of the equalizer. Equalization target pattern switching unit 5 comprising an equalizer 14, an equalization error calculation unit 4 for obtaining an equalization error from the equalization output and the equalization target pattern, and a phase synchronization signal generation unit for generating a system clock from the equalization output 6 A reproduction signal from the magnetic head 2 is supplied to a preamplifier 7, A
The signal is amplified by the GC circuit 9 and an unnecessary band is removed by the LPF 10. At this time, the gain of the AGC circuit 9 is subjected to negative feedback control so that the amplitude of the equalized output becomes a level necessary for identification.
The automatic equalizer 12 corrects the equalization characteristics including the characteristics of the PR waveform processing so as to reduce the equalization error obtained by means described later, and reproduces the data recorded by the discriminator 13 at the subsequent stage. . The above-described equalization error is obtained by subtracting a pattern value to be an equalization target from the output value of the equalizer. At this time, the output of the PR pattern conversion unit 15 is selected as the equalization target pattern value at the time of initial setting, and the output of the discriminator 13 is selected during the subsequent adaptive operation. As a result, the characteristics of the equalizer 12 are forcibly set to the equalization characteristics including the characteristics of the PR waveform processing at the initial stage, and thereafter the characteristics can be adaptively followed.

A second embodiment of the present invention will be described with reference to FIG. The reproduced signal from the magnetic head 2 is supplied to a preamplifier 7
The signal is amplified by the AGC circuit 9 and an unnecessary band is removed by the LPF 10. Further, this signal is input to the equalizer 12, where the equalization characteristics including the characteristics of the PR waveform processing are corrected so as to reduce the equalization error obtained by the same means as in FIG. It is digitized by the converter 11. This signal is output as reproduced data by a discriminator 13 such as a maximum likelihood decoder. At this time, the gain of the AGC circuit 9 is A / D
Negative feedback control is performed so that the output of the converter 11 becomes a level necessary for identification. Other configurations and operations are the same as those in FIG. According to the present embodiment, by providing the A / D converter 11 at the equalized output, application of the maximum likelihood decoder is facilitated, and improvement in device performance can be expected.

A third embodiment of the present invention will be described with reference to FIG. Since many parts are the same as in FIG. 2, only the differences will be described. In this embodiment, a simple discriminator 17 for performing discrimination on a bit-by-bit basis is provided at the output of the equalizer 12, and this is input to the equalization target pattern switching unit 5 instead of the output of the digital discriminator 13. When the maximum likelihood decoder is adopted as the classifier 13, it takes at least several bits of time from the input of the classification data to the output of the classification result, which causes a problem that it cannot follow a sudden change in the characteristic. According to the present embodiment, since the calculation of the equalization error at the time of the adaptive operation is sequentially obtained, it is possible to quickly follow the fluctuation of the characteristic.

A fourth embodiment of the present invention will be described with reference to FIG. Since many parts are the same as in FIG. 2, only the differences will be described. In this embodiment, an A / D converter 11 is provided at a stage subsequent to the LPF 10, and the automatic equalizer 12 is also digitized. According to the present embodiment, all the circuits at the subsequent stage from the automatic equalizer 12 can be digitized, thereby making it very easy to reduce the size of the circuit portion and greatly reducing the apparatus cost. Also, L
Since the output signal of the PF 10 has few high frequency components, A /
It is possible to reduce the error of the sample value due to the jitter of the D conversion sample signal. If the same level of sample jitter can be tolerated, the LPF inside the phase synchronization signal generator 6 can be simplified, for example, by digitization.
Normally, an equalizer using sample values is vulnerable to sample phase errors. For this reason, when external noise is superimposed on the sample signal, it has a significant effect on the equalized waveform. Therefore, in order to avoid the influence of external noise, the A / D converter 11 and the phase synchronization signal generator 6 are provided in the same IC.

A fifth embodiment of the present invention will be described with reference to FIGS. Since many parts are the same as in FIG. 2, only the differences will be described. FIG. 5 is a diagram illustrating the overall configuration of the present embodiment. In this embodiment, the equalizer 1 is used at the time of shipment or when the power is turned on.
Initialize the constant of 2. When initializing the equalization constant at the time of shipment, preset information is recorded for each track or sector on the magnetic disk 1 or for each of a plurality of tracks or sectors, and the equalization constant is obtained while reproducing the preset information.
A memory 18 for storing the constant is provided. This memory 1
8 is accessed immediately before data reproduction, and is set in the equalizer 12. In this case, the preset information after the completion of the initial setting may be deleted. In the case of initial setting when the power is turned on, preset information is recorded in each track or sector on the magnetic disk 1 or in a part of a plurality of tracks or sectors, and the memory 18 is reset when the power is turned on. In any case, the equalization constant may be updated adaptively while the data is being reproduced, and the updated constant may be rewritten in the memory 18 when the reproduction operation is completed. Further, the memory 18 may be an electrically writable nonvolatile memory.

FIG. 6 is a diagram showing a configuration of the automatic equalizer 12 according to the present embodiment. In the figure, reference numeral 20 denotes a delay element between each tap of the equalizer, 21 denotes a multiplier configured for each tap, 2
2 is an adder, 23 is a group of counters holding equalization constants, and the counters are provided in the same number as the number of multipliers so as to control the corresponding number of 21 multipliers. Numeral 24 is constant correction means for obtaining a constant update value. Since the equalizer of the present invention includes the PR waveform processing, the constants near the center tap become substantially equal, so the number of taps is set to an even number. The input signal 25 of the equalizer and the equalization error 28 are input to the constant correction means 24 for obtaining the updated value of the constant. Here, the sign of the input signal 25 of the equalizer and the sign of the equalization error 28 are equalized. A constant up / down signal 30 is obtained. Although not shown in the figure, this signal is provided for each counter. This signal updates the constant by up / down the counter holding the equalization constant.
The counter group 23 holding the constants is connected to the memory 18 storing the equalization constants by a bidirectional bus 27, and records the equalization constants of the automatic equalizer in the constant memory, or records them in the constant memory. Set and update the equalizer constant of the automatic equalizer with the set constant. According to the present embodiment, the data can be immediately reproduced only by setting the equalization constant from the memory 18. In addition, since the memory 18 is an electrically writable nonvolatile memory, it is not necessary to store data every time the power is turned on. Further, in the case of initial setting at the time of shipment, the area of the preset data may be deleted when the initial setting is completed, and this area can be used as a recording / reproducing area for user data. Therefore, the capacity of the device is increased, and effective and diversified use of the memory can be achieved. Further, since the preset information can be sufficiently obtained, the constant correction means 24 inside the equalizer can be realized with an extremely simple configuration. On the other hand, when the initial setting is performed every time the power is turned on, it is possible to appropriately cope with a case where the electromagnetic conversion characteristics greatly change over time.

[0017]

According to the present invention, an automatic equalizer including PR waveform processing is realized. This makes it possible to provide a reproduction signal processing circuit whose circuit can be simplified and which can be easily integrated into an IC.
Further, by applying a signal processing IC using this signal processing, a smaller magnetic recording / reproducing apparatus can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing a basic configuration of an embodiment of the present invention;
FIG.

FIG. 2 is a diagram showing a second embodiment of the present invention.

FIG. 3 is a diagram showing a third embodiment of the present invention.

FIG. 4 is a diagram showing a fourth embodiment of the present invention.

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

FIG. 6 is a diagram showing a configuration of an automatic equalizer according to a fifth embodiment of the present invention.

FIG. 7 is a diagram showing a conventional technique.

[Explanation of symbols]

1: magnetic disk, 2: magnetic head,
3 ... reproduction signal processing circuit 4 ... equalization error calculation unit 5 ... equalization target pattern switching unit 6 ... phase synchronization signal generation unit 7 ... preamplifier 8 ...
Fixed equalizer, 9 ... AGC circuit, 10 ...
LPF, 11: A / D converter, 12: Automatic equalizer, 13: Classifier, 14 ...
Pattern switcher, 15 ... PR pattern converter,
16: Preset pattern recording memory, 17: Simple discriminator, 18: Equalization constant memory, 20: Delay element, 21: Multiplier, 22: Adder, 23: Counter group holding constant, 24: Constant correcting means, 12 ': Conventional automatic equalizer.

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideki Sawaguchi 1-280 Higashi Koigakubo, Kokubunji-shi, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd. (56) References JP-A-57-57024 (JP, A) JP-A-55 −34304 (JP, A) JP-A-2-277323 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 20/10 321 G11B 5/09 321 H04L 25/497

Claims (9)

(57) [Claims] 1. A magnetic recording / reproducing apparatus having a reproduction signal processing circuit for obtaining an input from a magnetic head and outputting reproduction data via an amplifier circuit, an automatic equalizer, and a discriminator. A memory for recording a specific recording pattern for setting a pattern, a pattern converter for converting the recording pattern of the memory into an equalization target pattern corresponding to an equalized waveform after partial response waveform processing, and the pattern converter Calculating an output error of the automatic equalizer based on the output of the equalization target pattern, and including an equalization error calculation unit that controls a constant setting of the automatic equalizer to reduce the error.
Equalizing means corresponding to partial response waveform processing is added to the reproduction signal processing circuit, and the circuit configuration of the automatic equalizer includes equalizing means corresponding to the partial response waveform processing. Characteristic magnetic recording / reproducing device. 2. A magnetic recording / reproducing apparatus according to claim 1, wherein an A / D conversion circuit is provided between the automatic equalizer and the discriminator at a stage subsequent to the automatic equalizer, and the digital data is used to identify reproduced data. A magnetic recording / reproducing device comprising an identifier. 3. A magnetic recording / reproducing apparatus according to claim 2, further comprising a simple discriminator for outputting an identification result for each bit at an output of the automatic equalizer, and equalizing the output of the simple discriminator at the time of data reproduction. A magnetic recording / reproducing apparatus, wherein a characteristic of an automatic equalizer is sequentially corrected by using a target pattern for calculating an equalization error. 4. A magnetic recording / reproducing apparatus according to claim 1, wherein an A / D conversion circuit is provided before the automatic equalizer, and an automatic equalizer using a digital signal is provided. . 5. A magnetic recording / reproducing apparatus according to claim 1, further comprising a constant memory connected to an automatic equalizer, wherein an automatic equalization is performed by a memory constant recorded in said constant memory. A magnetic recording / reproducing apparatus comprising: means for setting an equalizer constant of an equalizer or updating the contents of a constant memory by updating an equalizer constant of an automatic equalizer. 6. The magnetic recording / reproducing apparatus according to claim 1, wherein the number of taps of the automatic equalizer is set to an even number. 7. A magnetic recording / reproducing apparatus according to claim 1, wherein said reproducing signal processing is performed together with a circuit configuration of an automatic equalizer including equalizing means corresponding to said partial response waveform processing. A magnetic recording / reproducing apparatus characterized by integrating circuits. 8. The reproduction signal processing of a magnetic recording / reproducing apparatus, wherein the equalization processing includes equalization corresponding to waveform processing of a partial response and equalization following other characteristic fluctuations in the reproduction signal processing. In a magnetic recording / reproducing apparatus, wherein the method is performed by including the following in one automatic equalization process. (1) The automatic equalizer corrects the equalization characteristic including the characteristic of the waveform processing of the partial response so as to reduce the equalization error. A discriminator identifies the corrected equalized output to obtain a reproduced data output. (2) An equalization error is obtained by subtracting a pattern value to be equalized from an output value of the automatic equalizer. (3)
As the pattern value to be the equalization target, a pattern value corresponding to the equalized waveform after the partial response waveform processing is selected at the time of initial setting, and the output of the discriminator is selected during the subsequent adaptive operation. (4) Partial response The pattern value corresponding to the equalized waveform after the waveform processing is obtained by recording a specific recording pattern for initial setting the characteristics of the automatic equalizer in a memory and converting the recording pattern in the memory. 9. A reproduction signal processing method for a magnetic recording / reproducing apparatus according to claim 8, wherein the setting of the equalization constant is performed as follows using a constant memory connected to an automatic equalizer. Signal processing method for a magnetic recording and reproducing apparatus. (1) While reproducing information recorded in a known pattern, a constant of an automatic equalizer is obtained and recorded in a constant memory. When reproducing data, the constant memory is read out and reset as an equalization constant. Alternatively, (2) the equalization constant reset with the contents of the constant memory is updated while reproducing data, and the contents of the constant memory are rewritten at the end of the reproduction operation.