JP3619335B2 - Recording equalizer and magnetic recording apparatus using the recording equalizer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an information recording technique used in a computer, an information processing apparatus, and the like, and in particular, a recording equalizer that corrects interference between adjacent codes that occurs when magnetic information is recorded in a magnetic recording apparatus, and the recording equalizer thereof The present invention relates to a magnetic recording apparatus comprising:
[0002]
[Prior art]
As a storage (recording) device for information equipment, a semiconductor memory and a magnetic recording device are mainly used. A semiconductor memory is used for the internal storage device from the viewpoint of access time, and a magnetic recording device is used for the external recording device because of its large capacity and non-volatility. The mainstream of current magnetic recording apparatuses is a magnetic disk and a magnetic tape. In order to record magnetic information on the magnetic recording medium of the magnetic recording apparatus, a functional unit having an electromagnetic conversion action is used. Further, in order to reproduce magnetic information from the magnetic memory, a functional unit using a magnetoresistance phenomenon, a giant magnetoresistance phenomenon, or an electromagnetic induction phenomenon is used. These functional units are provided in an input / output component called a magnetic head.
[0003]
The magnetic head has a function of moving relative to the magnetic recording medium, recording magnetic information at an arbitrary position on the magnetic recording medium, and electrically reproducing the magnetic information from the magnetic recording medium as necessary.
The performance of the storage device is determined by the speed and storage capacity at the time of input / output operation, and development is progressing with the aim of shortening the access time and increasing the storage capacity. In recent years, there has been a demand for miniaturization of storage devices from the viewpoint of space saving. In order to satisfy these requirements, it is necessary to develop a magnetic recording apparatus capable of recording and reproducing a large amount of magnetic information in a single magnetic recording medium.
[0004]
In order to realize high-density recording, it is necessary to reduce the size of magnetic domains written on the magnetic recording medium. This can be realized by narrowing the width of the magnetic pole that generates the recording magnetic field (narrowing the recording track width) and increasing the frequency of the current flowing through the coil that generates the recording magnetic field (decreasing the bit size).
However, it is known that adjacent codes interfere with each other as the frequency of the current flowing through the coil that generates the recording magnetic field is increased. As a countermeasure, a technique has been developed in which interference between codes is learned in advance, and the original information causing the interference is decoded from the shape of the reproduced waveform. This technique is generally called PRML (Partial Response Maximum Likelihood). This technique allows a plurality of pieces of information to be included in one reproduction waveform peak. For this reason, when performing the decoding, a highly accurate comparison process is necessary between the waveform learned in advance and the reproduced waveform. In order to perform this processing, it is necessary to match the timing of information existing in the waveform with the timing of the learned waveform with high accuracy. It can be easily imagined that if this timing is shifted, it is decoded into erroneous information.
[0005]
By the way, the reproduced waveform includes not only information “1” but also “0”. Therefore, only the peak position of the reproduced waveform is not the timing for comparing the waveforms. Therefore, it is necessary to match the timing even when “0” exists. In order to maintain this timing, a PLL circuit is used. The PLL circuit has a function of extracting a basic clock from an intermittent signal on a predetermined basic clock. By utilizing this function, the basic clock can be made to follow even if the frequency of the input signal changes. In the PRML signal processing technique, information is extracted from the reproduction waveform by performing a comparison process between the reproduction waveform and the learning waveform with reference to the basic clock from the PLL circuit.
[0006]
[Problems to be solved by the invention]
In the PRML signal processing technology, the reproduction waveform and the learning waveform are compared based on the basic clock. In recent years, when this technology is applied to extremely high frequencies, that is, when the interval between bits is narrow, interference occurs between adjacent codes, and the peak position of the reproduced waveform deviates from the peak position of the learned waveform. Occurred. This shift is called non-linear bit shift, and it is known that this shift amount differs depending on the relative speed between the storage medium and the magnetic head and the distance between adjacent codes. If this shift (peak position shift) occurs, the timing of the information present in the reproduced waveform and the timing of the learned waveform cannot be matched with high accuracy, so that malfunction is likely to occur and the reliability of the apparatus is increased. could not.
[0007]
This nonlinear bit shift will be described by taking a magnetic disk device as an example. In the magnetic disk device, the recording medium always rotates at a constant speed. Therefore, if recording is performed at the same frequency, the distance between adjacent codes differs between the inner peripheral side and the outer peripheral side. Therefore, in order not to make an extreme difference in the distance between adjacent codes, the area between the outer peripheral side and the inner peripheral side is divided into several zones, and the recording frequency is changed respectively. Nevertheless, the shift amount is not constant when the distance between adjacent codes is reduced (for realizing high-density recording), and uniform learning is difficult.
[0008]
In order to solve this problem, the distance between the codes where interference occurs between the codes is detected in advance, and when the information to be recorded corresponds to the distance between the codes, the phase of the recording current is intentionally delayed, Means for correcting the shift amount were taken. This technique is described, for example, in i-triple transaction on magnetics, Vol. 26, No. 5, 2298-2302 (IEEE TRANSACTION ON MAGNETICS, VOL. 26, No. 5, p. 2298-2302).
[0009]
FIG. 5 is a block diagram showing a configuration of a conventional recording equalizer 20. The data buffer 22 located in the preceding stage of the recording equalizer 20 stores the previous bit A (n−1) in addition to the recording target bit A (n) to be written. The bit determination circuit 23 determines only whether or not there is an information type in which information “1”, that is, a magnetization transition, exists in the previous bit A (n−1). In the subsequent shift amount calculation circuit 24, information “1” exists in the previous bit A (n−1) based on the peripheral speed and recording density information, and the recording target bit A (n) has information “1”. In this case, the time (shift amount Δ) for delaying the timing of the recording target bit A (n) is calculated. The calculated shift amount Δ is sent to the write current driver 25, and the write current driver 25 inverts the current polarity at the timing of (n + Δ) corresponding to the A (n) information.
[0010]
This conventional recording equalizer 20 improves the reduction (approach) of the inter-waveform distance caused by the phenomenon shown in FIG. 6 is a schematic cross-sectional view of the in-plane recording medium 30, in which a leftward magnetic domain 31 is written near the center of the medium magnetized in the rightward direction as indicated by arrows, and both sides of the magnetic domain 31 are shown. Fig. 6 schematically shows a state in which a magnetization transition is formed (written). It is assumed that the recording medium 30 is moving leftward at a speed v. Therefore, the magnetization transition on the left side is written before the magnetization transition on the right side.
[0011]
When a magnetization transition on the left side is formed, a magnetic charge is generated there. Next, when writing the magnetization transition on the right side, the leakage magnetic field from this magnetic charge is added to the writing magnetic field. The magnetization transition is formed by reversing the magnetization direction. Accordingly, the magnetostatic demagnetizing field from the previous bit acts in a direction to intensify the magnetic field for the next writing. For this reason, it is known that the magnetization transition always shifts in the previous bit direction.
[0012]
The peak position of the output signal 32 reproduced from these magnetization transitions shifts from the original position indicated by the broken line to the previous bit direction as indicated by the solid line as shown at the bottom of FIG. If this shift exists, as described above, an error occurs in the comparison processing with the learning waveform performed in the ML circuit, causing malfunction. In this way, the bit shift conventionally considered is only the shift in the previous bit direction. For this reason, as shown in FIG. 5, the countermeasure can calculate the shift amount to be corrected only by calculating the magnetostatic distance from the previous bit. For this reason, the recording equalizer 20 requires peripheral speed and recording density information necessary for calculating the distance to the previous magnetization transition.
[0013]
However, even if the timing of writing is controlled based on this principle, a new error occurs when writing higher density information. This error is 10 Gbit / in ² When realizing the above high-density recording, it can no longer be ignored.
An object of the present invention is to provide a means for correcting a new bit shift which becomes a problem when recording high-density information, and thereby a recording density of 10 Gb / in. ² It is to improve the reliability of the above high-density magnetic recording.
[0014]
[Means for Solving the Problems]
As a result of examining errors in high-density recording that cannot be corrected by bit shift in the backward bit direction based on the correction amount calculated from the distance between the front bits, the cause of this error is when writing magnetic information in a short time. In addition, it has been clarified that the magnetization reversal is delayed in a medium region where the effective magnetic field is weak (specifically, a region far from the recording gap of the magnetic head).
[0015]
FIG. 1 is a diagram for explaining the experimental results capturing this phenomenon, and shows the relationship between the pulse width of the write pulse and the length of the magnetic domain to be written. The horizontal axis in FIG. 1 represents the time width of the write pulse, and the vertical axis represents the size of the magnetic domain to be recorded. This experiment shows the result of measuring the size of the magnetic domain written directly under the magnetic head with a time interval analyzer with high accuracy by passing a unipolar current pulse through the magnetic head in a region uniformly magnetized in the opposite direction. It is. The experiment (writing) was performed by changing the peripheral speed (relative speed between the magnetic head and the medium) to 5 m / s, 1 m / s, and 0 m / s (stopped state).
[0016]
FIG. 1 shows that when the pulse width of the write pulse is 20 nm or more, the recording magnetic domain length increases in proportion to the increase in the pulse width. This increase is almost proportional to the peripheral speed. From this result, it can be said that the increase in the recording magnetic domain length coincides with the increase in the distance that the magnetic head has moved relative to the medium.
However, this tendency is not observed when the pulse width is shorter than 20 nm. That is, it has been clarified that the rate of decrease in the length of the magnetic domain to be written becomes more remarkable as the pulse width is shortened. Moreover, this phenomenon is consistent with all peripheral speeds and does not depend on the peripheral speed. This phenomenon indicates that the magnetic domain length does not increase linearly even when the magnetic head moves relative to the medium under the condition where the pulse width is shorter than 20 nm. The numerical value of pulse width 20 nm (frequency 25 MHz) shown in this experiment is a numerical value for this experimental system to the last, and it is natural that this value changes when the head magnetic pole material and medium conditions change.
[0017]
When the pulse width of the write pulse is short, it is estimated from the result that the magnetic domain length does not increase even when the magnetic head moves relative to the medium, and this phenomenon is considered that the inverted magnetic domain region has not grown to the predetermined range. be able to. By thinking in this way, it is possible to explain the result that the inverted magnetic domain lengths substantially coincide even when the peripheral speed is changed.
When this phenomenon occurs, the amount of expansion of the magnetization transition in the previous bit direction decreases, and the peak position shifts in the subsequent bit direction. Since this phenomenon is opposite to the magnetostatic shift direction described above, the error probability after decoding depends on whether or not this shift amount due to the delay in the magnetization reversal region is considered. Gave a big difference. This is 10Gb / in ² This is the reason why the reliability of the above high-density recording was lowered.
[0018]
The present invention has been made by investigating the cause of errors that occur during such high-density recording, such as recording that corrects interference between adjacent codes that occurs when magnetic information is recorded on a magnetic storage medium. The digitizer has a function of correcting a part of the phase of the output signal in the direction of advancement. The correction in the direction of advancing the phase of the output signal is performed in a recording current pulse width region where the rate of increase in the magnetic domain length is nonlinear and short with respect to the distance that the magnetic head moves with respect to the magnetic recording medium.
[0019]
The amount of phase advance is obtained based on the reversal time interval of the recording current, that is, the time width of the recording current pulse for forming the magnetic transition before and after the most adjacent on the medium.
The function of calculating the reversal time interval of the recording current from the recording information may be provided to the recording equalizer, or may be input to the recording equalizer from the outside.
Correction of the inversion timing of the recording current pulse corresponding to the recording target bit in the direction of the previous bit typically has no magnetic transition in the previous 1 bit of the recording target bit, and magnetic transition after the recording target bit Is performed when
[0020]
The timing for reversing the recording current pulse is calculated based on the time when the recording current pulse is reversed in order to record the previous bit.
The present invention also relates to a magnetic recording apparatus including a recording equalizer that corrects interference between adjacent codes of recording information, and a magnetic head that records and reproduces magnetic information on a magnetic recording medium by the output of the recording equalizer. The recording equalizer is used as a recording equalizer, and frequency information for forming a magnetic transition nearest to the recording equalizer on the magnetic recording medium is supplied to the recording equalizer. The recording equalizer obtains the recording pulse width from the frequency information calculated from the rotational speed of the magnetic recording medium, the radial position of the recording track, the recording density, etc., and the recording data before and after, and the recording pulse width is obtained in advance. When the pulse width is smaller than the current pulse width, the polarity inversion timing of the recording current is shifted by a predetermined amount in the previous bit direction. The shift amount is obtained on the basis of a relational expression or a table that is obtained in advance through experiments or the like.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 2 is a block diagram showing the basic configuration of the recording equalizer according to the present invention. The recording equalizer 1 according to the present invention includes at least a data buffer 2, front and rear bit determination circuits 3, a shift amount calculation circuit 5, and a write current driver circuit 6.
[0022]
Write data,..., A (n-1), A (n), A (n + 1),. Assuming that the write target bit is A (n), the data buffer 2 has at least the target bit A (n) and information on the previous bit A (n−1) and the subsequent bit A (n + 1). Stored. The data buffer 2 has a function of transmitting such information to the bit determination circuit 3 and the write current driver 6 located in the subsequent stage as needed.
[0023]
The bit determination circuit 3 has a function of determining whether or not there is an information type in which “1” of information, that is, a magnetization transition, exists in the previous bit A (n−1) and the subsequent bit A (n + 1). Here, the case of a recording method in which the case where there is a reversal of the write current polarity corresponds to information “1” will be described, but the same applies to other recording methods by detecting the presence of the information species to which the magnetization transition is written. Needless to say, it can be processed. In the bit determination circuit 3, there are four cases where there are magnetization transitions in the preceding and following bits, when there is a magnetization transition in the previous bit, when there is a magnetization transition in the subsequent bit, and when there is no magnetization transition in any of them. A signal is output corresponding to each case. This signal is supplied to the shift amount calculation circuit 5 located in the subsequent stage.
[0024]
The shift amount calculation circuit 5 calculates the timing of writing the target bit to be written based on the four types of output results from the bit determination circuit 3, and determines the shift amount Δ from the basic clock. This calculation takes into account a fundamental frequency (write frequency: PLL circuit frequency for writing) determined by the relative speed between the recording medium and the magnetic head and the closest recording density. Here, one of the features of the present invention is that the writing frequency (frequency information) is taken into account in calculating the bit shift amount. A method for calculating the shift amount will be described later.
[0025]
The shift amount Δ calculated by the shift amount calculation circuit 5 is sent to the write current driver 6. The write current driver 6 has a function of inverting the current polarity corresponding to the A (n) information. In the present invention, the current polarity inversion timing is advanced or delayed by the shift amount. In particular, the present invention is characterized in that it has a function of advancing the timing of current polarity reversal.
[0026]
FIG. 3 is a diagram comparing the write current pulse waveform of the present invention with the conventional write current pulse waveform. FIG. 3A shows a waveform of a current pulse for writing information A (-1) to A (4). As information, “111001” is described as an example. When this information is written, the shift amount due to the delay in the expansion of the magnetization inversion region occurs in the magnetization transitions of A (−1) and A (0) in which the pulse widths τ1 and τ2 are shortened. As for the magnetization transitions of A (1) and A (4), since the pulse widths τ3 and τ4 become longer, the magnetization transition is written at a predetermined position.
[0027]
In order to correct the shift of the magnetization transition of A (-1) and A (0), the inversion timings of the recording currents for writing A (-1) and A (0) according to the present invention are Δ1, Δ2 respectively in the previous bit direction. FIG. 3 (b) shows a waveform shifted by only the distance. According to this timing correction, even if the expansion of the magnetization inversion region is delayed, the magnetization transition point is detected at an early timing, so that no peak shift occurs in the reproduced waveform. Therefore, a reproduction waveform synchronized with the same basic clock as A (1) and A (4) is obtained.
[0028]
FIG. 3C shows a waveform according to a conventional bit shift correction method. Here, with respect to the write target bit A (0), when the previous bit A (-1) is considered as a reference, A (0) approaches A (-1), and therefore processing for delaying the timing by Δ3 is taken. . In this process, the process of delaying the timing of Δ4 is also taken for A (1) by moving the write target to A (1). As a result, even if Δ3 and Δ4 are the same, the time interval between A (−1) and A (0) and the time interval between A (0) and A (1) are considered based on A (−1). Will be different.
[0029]
In the waveform obtained by the present invention shown in FIG. 3B, if Δ1 and Δ2 are the same, the time interval between A (−1) and A (0) is A (0) and A (1). Is equal to the time interval. This process means that the timing of A (0) with respect to A (-1) and A (1) is preserved, and the improvement in timing extraction accuracy due to this effect becomes more prominent as the density information becomes higher. .
[0030]
Next, a method for calculating the shift amounts Δ1 and Δ2 shown in FIG. The experimental data shown in FIG. 1 was used for this calculation. First, the time interval until the magnetization reversal occurred at the bit at the rear position relative to the write target bit was obtained. This can be calculated from the timing at which the magnetization transition needs to be written in the subsequent bit position and the fundamental frequency of writing. This time interval corresponds to the pulse width taken on the horizontal axis of FIG. In this example, correction is performed when the pulse width is 20 nsec or less. The correction amount Δ is obtained from the time obtained by dividing the difference between the theoretical straight line and the actual magnetic domain length by the peripheral speed by applying the rate at which the magnetic domain length changes linearly when the pulse width is 20 nsec or more to the pulse width of 20 nsec or less. Asked. For example, when the peripheral speed of the magnetic recording medium is 5 m / s, the straight line α shown in the figure is a theoretical straight line, and recording is performed with the magnetic domain length obtained from the theoretical straight line α and the recording pulse width and the actual pulse width. The difference from the magnetic domain length is divided by the peripheral speed to be converted into time, and the polarity inversion timing of the recording current is corrected using the amount corresponding to that time as the shift amount.
[0031]
In order to calculate the correction amount Δ, the bit information at the rear position is necessary. However, in the example shown in FIG. 2, only the subsequent one bit information is used, and it is determined only whether the magnetization reversal exists at the next timing. did. This treatment is suitable for speeding up the processing, but it goes without saying that more back position information should be used in order to perform correction with higher accuracy.
This function of changing the timing of reversing the current polarity gives the write current driver 6 the function of measuring (counting) the time from the previous bit, and the current polarity when the time measurement value becomes the write clock ± shift amount. It can be easily realized by reversing. This function may be provided in the shift amount calculation circuit 5 or may be provided as an independent circuit between the shift amount calculation circuit 5 and the write current driver 6. In short, this function is a function for calculating the timing at which the recording current pulse is inverted based on the time at which the recording current pulse is inverted in order to record the previous bit, and is realized inside the recording equalizer 1. be able to.
[0032]
The above function can also be said to be a function of calculating the bit shift amount based on the reversal time interval of the recording current, that is, the time width of the recording current pulse for forming the magnetic transition before and after the most adjacent on the recording medium. This function is significantly different from the conventional function that calculates the shift amount only in the subsequent bit direction based on the spatial distance from the previous bit. This difference is advantageous in reducing intersymbol interference when writing high-density information.
[0033]
In order to realize this function, as described above, in the present invention, the recording equalizer 1 is provided with a function of calculating the reversal time interval of the recording current from the recording information. The same function can also be realized by inputting only the recording current inversion time interval information to the recording equalizer. For this purpose, a separate circuit that collectively calculates the inversion time interval information is required. However, when precoding processing is performed based on the intersymbol information before the recording equalizer, if the inversion time interval information is calculated based on the intersymbol information, the functional unit can be simplified and speeded up. Effective in terms.
[0034]
In the example shown in FIG. 2, the shift amount is calculated using the previous bit information. The previous bit information is for estimating the bit shift amount due to the magnetostatic reaction as in the conventional method. This correction was not necessary when recording low-density information, but when recording high-density information, magnetostatic action is added and the expansion of magnetization is promoted. A measure was taken to account for the amount of correction in the rear bit direction. The estimation of the correction amount in consideration of this magnetostatic action is the same as in the conventional method. Therefore, the circuit configuration necessary for that is omitted here. As described above, the feature of the present invention is that the bit position in the previous bit direction is corrected, and this correction corrects the bit shift caused by the expansion difference of the magnetization switching region.
[0035]
FIG. 4 is a block diagram showing an overall view of the signal processing circuit. The recording information (data) first enters the modulator 7. The modulator 7 processes the original data according to a predetermined rule so that no more than a predetermined number of “0” information exists. This output is sent to the precoder 8. The precoder 8 processes the data into a code that is strong against interference between adjacent signals. For example, information such as “00100” is equalized to be “001100”. Here, the output signal from the precoder 8 is referred to as A (n). The A (n) signal is sent to the recording equalizer 1. The processing in the recording equalizer 1 is as described above.
[0036]
The output from the recording equalizer 1 is defined as A (n−Δ). Here, Δ represents the difference (shift amount) between the write clock and the timing for executing the actual write operation. The shift amount Δ is calculated and controlled by the recording equalizer 1. The output from the write current driver provided at the last stage of the recording equalizer 1 is sent to the magnetic head 9, where it is converted into magnetic information by an electromagnetic conversion action and written to the recording medium.
[0037]
At the time of reading, the magnetic information written on the recording medium is converted again into an electric signal using the electromagnetic conversion action of the magnetic head 9. Since the electrical signal here is weak, it is first amplified by the preamplifier circuit 10 and then enters the PR equalization circuit 11 and the ML decoding circuit 12. The PR equalization circuit 11 performs conversion reverse to the processing in the precoder 8. For example, information “001100” is inversely converted to “00100”. At this time, the information is converted into “1” and “0” information by performing a comparison process between the reproduced waveform and the learning waveform in which intersymbol interference is taken in advance. In the ML decoding circuit 12, the reproduced information is decoded according to a predetermined rule based on the preceding and following several bit information.
[0038]
These PR equalization circuit 11 and ML decoding circuit 12 need to operate at a fixed timing. It is easy to understand that if this timing goes wrong, it will be decoded into incorrect information. For this reason, the PR equalization circuit 11 and the ML decoding circuit 12 have a timing to operate using a common VCO 13 (voltage controlled oscillator) output. Finally, information is sequentially input to the demodulating circuit 14 and inversely converted into a form of the first recording information (a form including a series of “0”).
[0039]
The signal processing flow of the signal processing circuit shown in FIG. 4 is basically the same as that of the conventional PRML signal processing apparatus, but the output from the recording equalizer 1 includes a shift in the previous bit direction. The difference is that frequency information (in other words, time information until writing the magnetization transition) is used for calculating the shift amount. In particular, as described above, when there is no magnetic transition in the first bit before the recording target bit and the magnetic transition continues after the recording target bit, the timing for inverting the current pulse is shifted in the previous bit direction. This point is specific to the present invention.
[0040]
As a result of applying the recording equalizer shown in FIG. 2 to the magnetic disk device having the signal processing circuit shown in FIG. 4, 10 Gb / in ² Class high recording density. In this recording equalizer, since the bit shift amount is determined only by the writing frequency except for past and future information, the bit shift amount can be finely corrected from a simple sequence under any peripheral speed condition. Accordingly, since it is not necessary to rearrange the calculated values for each of the inner and outer peripheral conditions as in the prior art, it is possible to reduce the number of parts, reduce the price, and increase the speed of the apparatus.
[0041]
【The invention's effect】
According to the present invention, a reliable 10 Gb / in ² Class high recording density storage device can be realized. Also, by using the recording equalizer of the present invention, the bit shift amount can be finely corrected from a simple sequence under any peripheral speed condition.
[Brief description of the drawings]
FIG. 1 is a diagram showing a relationship between a reversal time of a write pulse and a magnetic domain length to be written.
FIG. 2 is a block diagram showing a basic configuration of a recording equalizer according to the present invention.
FIG. 3 is a diagram showing a comparison between a write current pulse waveform according to the present invention and a conventional write current pulse waveform.
FIG. 4 is a block diagram showing an overall view of a signal processing circuit.
FIG. 5 is a block diagram showing a configuration of a conventional recording equalizer.
FIG. 6 is an explanatory diagram of a bit shift that occurs for magnetostatic reasons.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Recording equalizer, 2 ... Data buffer, 3 ... Bit determination circuit, 5 ... Shift amount calculation circuit, 6 ... Write-current driver, 7 ... Modulation circuit, 8 ... Precoder, 9 ... Magnetic head, 10 ... Preamplifier, 11 ... PR equalizer, 12 ... ML decoder, 13 ... VCO (voltage / frequency converter), 14 ... demodulator, 20 ... conventional recording equalizer, 22 ... data buffer, 23 ... bit decision circuit, 24 ... Shift amount calculation circuit, 25... Write current pulse, 30... Recording medium, 31.

Claims (8)

In the recording equalizer to correct the interference between adjacent codes generated when recording magnetic information on a magnetic storage medium, have a function for correcting the direction of advancing the portion of the phase of the output signal, the phase of the output signal The recording equalizer according to claim 1 , wherein the correction in the advancing direction is performed in a short recording current pulse width region in which an increase amount of the magnetic domain length is nonlinear with respect to an amount of movement of the magnetic head with respect to the magnetic recording medium . 2. A recording equalizer according to claim 1, wherein the recording current pulse width is shorter than 17.5 nsec. 3. The recording equalizer according to claim 1, wherein the phase advance amount is obtained based on an inversion time interval of the recording current. 4. The recording equalizer according to claim 3, wherein the recording equalizer has a function of calculating an inversion time interval of the recording current from the recording information. 4. The recording equalizer according to claim 1, wherein reversal time interval information of the recording current is input. When the magnetic transition does not exist in one bit before the recording target bit and the magnetic transition continues after the recording target bit, the inversion timing of the recording current pulse corresponding to the recording target bit is corrected in the previous bit direction. 4. The recording equalizer according to claim 1, wherein the recording equalizer is used. 4. The recording equalizer according to claim 1, wherein timing for inverting the recording current pulse is calculated on the basis of the time when the recording current pulse is inverted in order to record the previous bit. In the magnetic recording apparatus, comprising: a recording equalizer that corrects interference between adjacent codes of recording information; and a magnetic head that records and reproduces magnetic information on a magnetic recording medium by the output of the recording equalizer. The recording equalizer according to any one of claims 1 to 7, wherein the recording equalizer has frequency information for forming the nearest magnetic transition on the magnetic recording medium. A magnetic recording apparatus that is supplied.

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