JPH11161905A - Recording level setting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a recording level setting method nearly fixing a magnetization state of a magnetic tape recorded with a signal regardless of a difference in a magnetic head and performing with simple operation without complex regenerative signal processing. SOLUTION: In the recording level setting method applied to a magnetic recording/reproducing device recording/reproducing a digital signal and setting a signal level recorded on a magnetic record medium, the signal level at the time of recording with the magnetic head is set so that a first reproducing level when the record medium recording a rectangular wave of a sufficiently low single specified frequency without causing waveform interference selected from the frequency band of the digital signal at a prescribed level is reproduced by the magnetic head nearly coincides with a second reproducing level when the rectangular wave of the single specified frequency is self recorded and reproduced by the magnetic head on the recording medium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for setting a signal level to be recorded on a magnetic recording medium in a magnetic recording and reproducing apparatus for recording and reproducing digital signals.

[0002]

2. Description of the Related Art Hitherto, a helical scan type azimuth recording digital data recording / reproducing apparatus (also referred to as a data recorder) has been studied and put to practical use. A method for maintaining compatibility between devices has also been studied. Generally, such data recorders transcode the data and pulse record it on a magnetic tape. At the time of reproduction, the reproduced signal is shaped (waveform equalized) through a waveform equalizer, converted into a binary digital signal, and then the clock is reproduced, and the recorded data is restored.

In waveform equalization, in many cases, a waveform is shaped using a transversal filter so as not to interfere with adjacent bits. At this time, the waveform equalizer
It has a certain frequency characteristic and phase characteristic. That is, if the frequency characteristic and the phase characteristic of the reproduced signal are constant, the same equalized waveform output can be always obtained.
Conversely, when the frequency / phase characteristics of the reproduced signal change, the equalized output also changes, and as a result, the S / N deteriorates and the error rate increases.

For this reason, as a waveform equalizer, a tracking type automatic equalizer circuit is used to make the equalization output characteristics constant even when the circuit scale is increased, or to perform maximum likelihood decoding. Efforts have been made to absorb differences in frequency and phase characteristics. On the other hand, as the recording density increases, if the intensity of magnetization on the magnetic tape is different, the difference tends to appear as a difference in frequency / phase characteristics during reproduction. Even under the premise that the characteristics of the magnetic tapes are the same, the intensity of the magnetization is different due to the difference in the characteristics of the individual magnetic heads constituting the electromagnetic-to-electromagnetic converter. Therefore,
Good results are often not obtained simply by giving a fixed number of unspecified heads a certain equalization characteristic.

Therefore, in order to obtain the compatibility of the apparatus, conventionally, generally, attention is paid to a signal having the shortest recording wavelength, and an optimum recording current is set so that the output level and C / N of the signal become specified values. By doing so, the recording level has been determined.

[0006]

However, in this method, the shortest recording wavelength is a signal subjected to the largest waveform interference, and the manner of receiving the waveform interference varies depending on the individual characteristics of the magnetic head. Looking at the frequency and phase characteristics over the entire region, the magnetic heads differed from one another. Therefore, such a method is insufficient to keep the frequency / phase characteristics of the reproduced signal between different magnetic heads constant.

[0007] Alternatively, a method of setting several kinds of frequencies in the output of the fixed equalizer and setting the recording level so that their output ratio is constant can be considered, but the operation is complicated and requires a long time. Adjustment was necessary, which was not always preferable.

To solve these problems, the state of magnetization of a magnetic tape on which a signal is recorded is made substantially constant irrespective of the difference between magnetic heads, and complicated reproduction signal processing is not required.
There has been a demand for a recording level setting method that can be performed with a simple operation.

[0009]

In order to solve the above-mentioned problems, a recording level setting method according to the present invention is applied to a magnetic recording / reproducing apparatus for recording / reproducing a digital signal, and sets a signal level to be recorded on a magnetic recording medium. In the recording level setting method, a rectangular wave of a single specific frequency, which is selected from the frequency band of the digital signal and which is low enough to cause no waveform interference, is recorded at a predetermined level when the recording medium is reproduced by a magnetic head. 1 by the magnetic head so that the reproduction level 1 and the second reproduction level when the single rectangular wave of the single specific frequency is self-recorded and reproduced by the magnetic head on the recording medium substantially coincide with each other. The signal level at the time is set.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a recording level setting method according to the present invention will be described by way of a preferred embodiment with reference to the accompanying drawings.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a recording level setting method according to the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 shows a case where a plurality of recording heads having different magnetic core materials and gap lengths are used, and the recording current intensity is changed.
5 is a graph showing the relationship between the output level of a reproduced signal and the half-value width of the reproduced signal when a signal of 0 kHz is recorded and reproduced by a single reproducing head. This relationship has been obtained experimentally.

First, the graph of FIG. 1 will be described. The signal band of the magnetic recording / reproducing apparatus targeted by the present invention is approximately 1
It is assumed that the frequency is 0 MHz.

Here, the shortest recording wavelength (frequency is 10 MHz)
for example, 25 times the wavelength (frequency is 400 kHz)
z). The numerical value of this wavelength is
In the reproduction amplifier output signal, the wavelength is selected so as to be located at a position where the power is relatively large and to be a wavelength that is hardly affected by waveform interference.

Is to prevent the influence of the frequency attenuation characteristics of the rotary transformer and the electric circuit.
Means that the characteristic differences of the head are absorbed by removing the waveform interference. Four recording heads were used. In any of the heads, the track width is 32 μm.

The first recording head is a MIG type head, and its gap length is 0.15 μm. The results obtained with this head are represented by は for the L-channel and by ● for the R-channel. The second recording head is a MIG type head, and its gap length is 0.15 μm. The results obtained with this head are as follows:
Channels are represented by ■.

The third recording head is a MIG type head, and its gap length is 0.20 μm. The results obtained with this head are indicated by Δ for the L-channel and Δ for the R-channel. The fourth recording head is a ferrite head, and its gap length is 0.31 μm.
The results obtained with this head are:
-Channels are represented by ◆.

The recording signal level supplied to each channel of each recording head is appropriately set to three levels (relatively -2 dB,
0 dB, 2 dB) and select 4 levels
The 00 kHz signal was recorded on a magnetic tape. This magnetic tape was reproduced by a reproducing head, and the output level (mVpp) and half-width W50 (nm) of the obtained reproduced signal corresponding to each channel of each recording head are plotted in FIG. The reproducing head was a ferrite head, the track width of which was 32 μm, and the gap length was 0.31.
μm.

As is clear from FIG. 1, when signals recorded by four types of recording heads are reproduced using a certain reproducing head, the output level and the half-value width correspond well at this frequency. I understand. This indicates that, when the reproduction level is made equal by appropriately selecting the recording signal level for each recording head at a low frequency that does not receive waveform interference, the half-width becomes equal. For example,
The half width W50 of 105-110 nm is 600 mVpp as the reproduction output, but the recording signal level of each recording head may be selected in such a manner.

The isolated reproduction wave is the impulse response itself of the reproduction system, and the half-value width determines the frequency / phase characteristics. Therefore, if data is recorded by selecting a recording current level value at which the same reproduction level can be obtained, the frequency / phase characteristics, that is, the state of magnetization on the tape becomes the same regardless of the head.

The following shows that this has been confirmed experimentally. FIG. 2 shows a case where the recording levels of a plurality of recording heads in FIG. 1 are selected so that the reproduction signal output level is 600 mVpp, and each recording head records an M-sequence signal. 3 shows a frequency spectrum when reproduced by.

Assuming that the recording signal level of the fourth recording head is 0 dB when the reproduction signal output level is set to 600 mVpp, the recording signal level of the first recording head is 2 dB, and the recording of the second recording head is Signal level is 0d
B, the recording signal level of the third recording head was -2 dB, and each recording head was set to the corresponding recording signal level. The half width is in the range of 105 to 110 nm.

FIG. 2 shows that the reproduction frequency characteristic of the M-sequence signal recorded by the four recording heads is within 1 dB in all frequency bands, indicating that sufficient compatibility is shown. . From the above experimental results, in this method, the recording signal level may be set as follows.

First, a reference tape is prepared. Pulse recording is performed on the reference tape at a wavelength, for example, 25 times the shortest recording wavelength. The recording level is set to a level at which a sufficient S / N can be secured in a practical use state and a low data error rate is confirmed.

Next, in each of the recording devices, the same reproduction level as when reproducing the reference tape is used.
The recording level is determined so that it can be obtained by self-recording on the tape. In this way, it is possible to make the magnetization state on the tape constant during recording regardless of the individual characteristics of the recording head.

FIG. 3 is a diagram showing the relationship between azimuth loss and frequency when the azimuth error between the recording and reproducing heads is 30 'in azimuth recording. In FIG. 3, when the gain at the time of self-recording and reproduction is 0 dB, the azimuth error is 30 when the relative speed between the tape and the head is 5.8 m / sec when the azimuth angle is 10 ° and 30 °. 'The frequency dependence of the attenuation when it occurs is shown.

As described above, in the present invention, since the wavelength recorded on the reference tape is relatively or extremely large (for example, 400 kHz), as can be seen from FIG. . Considering that azimuth recording is common from the viewpoint of improving the recording density, even if the azimuth has a relatively large angle, according to the recording current level setting method of the present invention, the alignment error The feature is that it can be reduced. Even if there is an azimuth error between the reference tape and the head of each device, the magnetization state can be kept constant without being affected.

[0027]

As described above, the recording level setting method according to the present invention is applied to a magnetic recording / reproducing apparatus for recording / reproducing a digital signal, and sets a signal level for recording on a magnetic recording medium. In the method, a first reproduction level when a recording medium on which a rectangular wave of a specific frequency which is low enough to cause no waveform interference and which is selected from a frequency band of a digital signal is recorded at a predetermined level, is reproduced by a magnetic head. And a second reproduction level when the single rectangular wave of the specific frequency is self-recorded and reproduced by the magnetic head on the recording medium so as to substantially coincide with each other.
By setting the signal level at the time of recording by the magnetic head, the magnetization state of the magnetic tape on which the signal is recorded is made substantially constant regardless of the difference of the magnetic head, and no complicated reproduction signal processing is required, thereby simplifying the operation. It is possible to provide a recording level setting method that can be performed by simple operations.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a method of using a plurality of recording heads having different magnetic core materials and gap lengths and changing the recording current intensity to 400 k.
6 is a graph showing the relationship between the output level of a reproduced signal and the half width of the reproduced signal when a signal of Hz is recorded and reproduced by a single reproducing head.

FIG. 2 shows a case where the recording levels of a plurality of recording heads in FIG. 1 are selected such that a reproduction signal output level is 600 mVpp, and an M-sequence signal is recorded by each recording head; 3 shows a frequency spectrum when reproduced by.

FIG. 3 is a diagram illustrating a relationship between azimuth loss and frequency when an azimuth error between recording and reproducing heads is 30 ′ in azimuth recording.

Claims (1)

[Claims] 1. A recording level setting method applied to a magnetic recording / reproducing apparatus for recording / reproducing a digital signal and setting a signal level to be recorded on a magnetic recording medium, the method comprising: generating a waveform interference selected from a frequency band of the digital signal. A first reproduction level when a recording medium on which a single specific frequency square wave having a sufficiently low frequency is recorded at a predetermined level is reproduced by a magnetic head, and the single specific frequency square wave on the recording medium; A recording level setting method, wherein a signal level at the time of recording by the magnetic head is set so that a second reproduction level at the time of self-recording and reproduction by the magnetic head substantially coincides with the second reproduction level.