JPH087209A - Digital magnetic recording / reproducing device - Google Patents

Abstract

(57) [Abstract] [Purpose] In a digital magnetic recording / reproducing apparatus using a class 4 partial response method, both an equalization error and noise enhancement due to waveform equalization are suppressed and an error rate is improved. In a digital magnetic recording / reproducing apparatus using a class 4 partial response system having an electromagnetic conversion system including a magnetic head and a magnetic recording medium, an output value at a Nyquist frequency f _N of the electromagnetic conversion system and a half Nyquist frequency f _N The output difference between the output values at _{/ 2} is 3 to 7 dB, and more preferably 4 to 6 dB.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital magnetic recording / reproducing apparatus using a class 4 partial response system.

[0002]

2. Description of the Related Art The partial response system is a high-density digital recording system in which the recording density is improved by intentionally adding intersymbol interference. Among the partial response systems, the class 4 partial response system (hereinafter referred to as P
It is called R4 method. ) Has excellent characteristics such as no direct current component and good SN ratio.

A digital magnetic recording / reproducing apparatus using the PR4 system comprises a precoder, a recording amplifier, an electromagnetic conversion system including a magnetic head and a magnetic recording medium, a reproducing amplifier, a waveform equalizer, and a discriminator. .

At the time of recording, the recording digital signal passes through a precoder corresponding to the PR4 system having a transfer function of 1 / (1-D ² ) and then adjusted to an optimum recording current by a recording amplifier. . Then, in the electromagnetic conversion system, a digital signal is recorded on the magnetic recording medium by the magnetic head.

During reproduction, the signal recorded on the magnetic recording medium by the PR4 system is reproduced by the magnetic head in the electromagnetic conversion system. Then, after the reproduction output signal passes through the reproduction amplifier, the waveform equalizer P
Waveform equalization is performed so as to satisfy the R4 standard. Then, the signal is discriminated by the discriminator, demodulated into a reproduced digital signal and reproduced.

In such a digital magnetic recording / reproducing apparatus,
FIG. 6 shows an example of the amplitude frequency characteristics of the outputs of the waveform equalizer and the electromagnetic conversion system. The transmission rate is 40 Mbit /
Second, the relative speed between the magnetic head and the magnetic recording medium is 10 m /
s, the gap length of the magnetic head is 0.2 μm.

In FIG. 6, a characteristic C is the amplitude frequency characteristic of the output of the waveform equalizer (PR4 equalization reference spectrum), and a characteristic D is the amplitude frequency of the output of the electromagnetic conversion system including the magnetic head and the magnetic recording medium. It is a characteristic.

In this digital magnetic recording / reproducing apparatus, the Nyquist frequency f _N (half the recording bit frequency) is 20 MHz, and the half Nyquist frequency f
_{N / 2} (1/4 frequency of recorded bit frequency) is 10 MH
z.

The characteristic C, which is the amplitude frequency characteristic of the output of the waveform equalizer, is approximately half the Nyquist frequency f _{N / 2.}
It has a peak at and a characteristic that it decreases as the frequency increases from the peak or as the frequency decreases from the peak. On the other hand, the characteristic D, which is the amplitude frequency characteristic of the output of the electromagnetic conversion system, has a peak at a frequency slightly lower than the half Nyquist frequency f _{N / 2} , and the frequency increases from the peak or decreases from the peak. The characteristic is shown to decrease in the direction.

[0010]

By the way, the waveform equalizer performs waveform equalization so that the amplitude frequency characteristic of the output of the electromagnetic conversion system is matched with the PR4 equalization standard. However, if the waveform equalizer does not have a sufficient correction capability, the equalization error increases, which causes the error rate to deteriorate. Further, the noise included in the reproduction output signal of the electromagnetic conversion system is emphasized when performing waveform equalization in the waveform equalizer,
It becomes a factor that deteriorates the error rate. That is, the equalization error due to the waveform equalization and the emphasis of noise have a great influence on the error rate.

However, it is difficult to eliminate the equalization error by realizing near-ideal waveform equalization with the waveform equalizer. Further, in order to reduce the equalization error, it is necessary to increase the circuit scale of the waveform equalizer, and as a result, noise increases, which causes a problem that the error rate deteriorates. Therefore, in the conventional digital magnetic recording / reproducing apparatus using the PR4 system, it is difficult to improve the error rate, and it is becoming difficult to cope with higher density recording such as in a high definition television.

Therefore, the present invention has been proposed in view of such conventional circumstances, and digital magnetic recording in which equalization error and noise enhancement due to waveform equalization are suppressed and an error rate is improved. An object is to provide a reproducing device.

[0013]

Means for Solving the Problems] output amplitude frequency characteristic of the electromagnetic conversion system, generally, the output difference between the output value of the output value and half the Nyquist frequency f _{N / 2} at the Nyquist frequency f _N (hereinafter, this output difference " It is possible to define the characteristic by "f characteristic"), and it has been conventionally said that the smaller the f characteristic, the better.

However, as a result of intensive studies by the present inventors in order to achieve the above-mentioned object, it has been found that the smaller this f characteristic is, the better, and that f, in particular, has an optimum constant value. The present invention has been completed based on this finding.

That is, the digital magnetic recording / reproducing apparatus of the present invention has an electromagnetic conversion system including a magnetic head and a magnetic recording medium. In the digital magnetic recording / reproducing apparatus using the PR4 system, the Nyquist frequency f _N of the electromagnetic conversion system is used. Of the output value at the half Nyquist frequency f _{N / 2} is 3 to 7 dB, more preferably 4 to
It is 6 dB.

Note that, for example, when the film thickness of the magnetic layer of the magnetic recording medium is increased, the thickness of the oxide layer on the surface of the magnetic recording medium is increased, or when a vapor deposition medium is used as the magnetic recording medium, the characteristic is f. It is possible to change the value by increasing the incident angle of vapor deposition, increasing the thickness of the protective film of the vapor deposition medium, or increasing the gap length of the magnetic head. And f special 3-
7 dB, more preferably 4 to 6 dB.

[0017]

[Function] f characteristic is 3 to 7 dB, more preferably 4 to 6 dB
By defining the above, the equalization error and the noise emphasis due to the waveform equalization of the digital magnetic recording / reproducing apparatus are suppressed, and the error rate is improved.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments to which the present invention is applied will be described in detail below with reference to the drawings.

The digital magnetic recording / reproducing apparatus of this embodiment is
As shown in FIG. 1, the precoder 10 and the recording amplifier 1
1, an electromagnetic conversion system 17 including a magnetic head 12 and a magnetic recording medium 13, a reproduction amplifier 14, a waveform equalizer 15,
It consists of a discriminator 16.

At the time of recording, the recording digital signal 1 is PR4 having a transfer function of 1 / (1-D ² ).
After passing through the precoder 10 corresponding to the method, the recording amplifier 11 adjusts the recording current to an optimum value. Then, in the electromagnetic conversion system 17, the magnetic head 12 records a signal on the magnetic recording medium 13.

During reproduction, the signal recorded on the magnetic recording medium 13 by the PR4 system is reproduced by the magnetic head 12 in the electromagnetic conversion system 17. Then, after the reproduction output signal 2 passes through the reproduction amplifier 14,
The waveform equalizer 15 equalizes the waveform so as to satisfy the PR4 standard. Then, this signal is discriminated by the discriminator 16 and demodulated into the reproduced digital signal 3 and reproduced.

In order to make the amplitude-frequency characteristics of the output of the electromagnetic conversion system in such a digital magnetic recording / reproducing apparatus suitable for the PR4 system, for example, the magnetic recording layer is thickened in the magnetic recording medium. If the thickness of the oxide layer on the medium surface is increased, or if a vapor deposition medium is used as the magnetic recording medium, the incident angle of vapor deposition is increased, the thickness of the protective film of the vapor deposition medium is increased, or the magnetic head Depending on the method such as increasing the gap length, the f characteristic is 3 to 7d.
It is controlled so that it becomes B.

Characteristic A and characteristic B are shown in FIG. 2 as an example of controlling the amplitude frequency characteristic of the output of the electromagnetic conversion system in this way. The transmission rate is 40 megabits / second, the relative speed between the magnetic head and the magnetic recording medium is 10 m / s, the gap length between the magnetic heads is 0.2 μm, and the Nyquist frequency f
_N is 20 MHz and half Nyquist frequency f _{N / 2} is 10
MHz. The f-characteristic of the characteristic A is about 5 dB, and the f-characteristic of the characteristic B is about 3 dB.

Evaluation of Error Rate The error rate of such a digital magnetic recording / reproducing apparatus was evaluated.

First, the change of the equalization error power amount with respect to the value of f characteristic of such an electromagnetic conversion system was examined. The results are shown in Fig. 3. From FIG. 3, it can be seen that f characteristic is about 6 dB from the viewpoint of suppressing the amount of equalization error power.

Next, the change in the amount of noise enhancement with respect to the value of f characteristic of such an electromagnetic conversion system was examined. FIG. 4 shows the results.
From FIG. 4, it can be seen that the f characteristic is optimally about 3 dB from the viewpoint of suppressing the noise emphasis amount.

Then, regarding such an electromagnetic conversion system,
Considering the effects of both the equalization error power amount and the noise enhancement amount, the change in the error rate with respect to the value of f when the SN ratio at the half Nyquist frequency f _{N / 2} is fixed was examined. Results are shown in FIG. From this FIG. 5, f characteristic is 3
In the case of ~ 7 dB, the error rate becomes small and f characteristic is 3
It can be seen that the error rate becomes large when it becomes smaller than dB or becomes larger than 7 dB. It can be seen that the error rate becomes even smaller when the f-characteristic is 4 to 6 dB, and becomes extremely small when the f-characteristic is approximately 5 dB.

Accordingly, the error rate of the digital magnetic recording / reproducing apparatus having the characteristic B of f characteristic of about 3 dB is small. Then, the error rate of the digital magnetic recording / reproducing apparatus having the characteristic A of f characteristic of about 5 dB is further reduced.

As described above, when the output amplitude frequency characteristic of the PR4 type electromagnetic conversion system is set in the range of 3 to 7 dB, more preferably 4 to 6 dB, the amplitude frequency characteristic of the output of the electromagnetic conversion system is set. Is suitable for the PR4 system, both equalization error and noise enhancement can be suppressed, and the error rate can be reduced.

[0030]

As is apparent from the above description, according to the present invention, both the equalization error due to the waveform equalization and the emphasis of the noise included in the reproduction output signal can be suppressed, and the digital magnetic recording can be easily performed. The SN ratio of the playback device can be improved. Therefore, the error rate can be reduced and higher density recording can be performed.

Since an excellent error rate can be realized without increasing the circuit scale of the waveform equalizer,
The circuit of the waveform equalizer can be simplified.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration example of a digital magnetic recording / reproducing apparatus to which the present invention is applied.

FIG. 2 is a characteristic diagram showing an example of an amplitude frequency characteristic of an output of an electromagnetic conversion system of a digital magnetic recording / reproducing apparatus to which the present invention is applied.

FIG. 3 is a characteristic diagram showing the f-characteristic dependency of the equalization error power amount.

FIG. 4 is a characteristic diagram showing the f characteristic dependency of the amount of noise enhancement.

FIG. 5 is a characteristic diagram showing f-characteristic dependency of an error rate.

FIG. 6 is a characteristic diagram showing amplitude frequency characteristics of outputs of an electromagnetic conversion system and a waveform equalizer of a conventional digital magnetic recording / reproducing apparatus.

[Explanation of symbols]

 1 recording digital signal 2 reproduction output signal 3 reproduction digital signal 10 precoder 11 recording amplifier 12 magnetic head 13 magnetic recording medium 14 reproduction amplifier 15 waveform equalizer 16 discriminator 17 electromagnetic conversion system

Claims (2)

[Claims] 1. A digital magnetic recording / reproducing apparatus using a class 4 partial response system having an electromagnetic conversion system including a magnetic head and a magnetic recording medium, wherein an output value at a Nyquist frequency and an output at a half Nyquist frequency of the electromagnetic conversion system. Output value difference is 3 to 7 dB
A digital magnetic recording / reproducing apparatus characterized by: 2. The digital magnetic recording / reproducing apparatus according to claim 1, wherein the output difference is 4 to 6 dB.