JP2004288370A - Digital signal magnetic recording / reproducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure overwrite characteristics equivalent to a vapor deposited tape by improving the overwrite characteristics of a coated tape by using the recording current and to use both the coated and the vapor deposited tapes. <P>SOLUTION: The recording current value of a recording current setting circuit 4 is set to a range larger than the recording current in which the reproducing signal level of the frequency equivalent to the shortest recording wavelength of digital signals to be recorded becomes the maximum, by +1dB or greater. Then, the signals are recorded on a coated tape 6 having a magnetic layer thickness, which is equal to or less than 0.2μm, via a magnetic head 5 so as to obtain the overwrite characteristics equivalent to a vapor deposited tape. During reproducing, a switching circuit 10 is used to select either the output of a vapor deposited tape EQ circuit 8 or the output of a coated tape EQ circuit 9 according to the output of a tape kind detecting circuit 12. Moreover, by switching the control loop gain of a tracking control circuit 11 for each tape kind, the use of both tapes is made possible. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a magnetic recording / reproducing apparatus for digital signals which defines a recording current of a magnetic recording medium to be used and corresponds to two kinds of tapes, a vapor-deposited tape and a coated tape.

  As an example of a conventional digital signal magnetic recording / reproducing apparatus that enables overwrite recording only with a recording head without using an erasing head, a Digital Audio Tape system (DAT) is conceivable (for example, see Non-Patent Document 1).

  In DAT, in order to enable overwrite recording, an area for recording a pilot signal for detecting a recording track position and a data area for recording data information are provided, and a wavelength at which an overwrite characteristic is easily obtained is selected. .

  That is, the shortest wavelength and the longest wavelength of the data pattern to be recorded are set as follows to make it easy to obtain the overwrite characteristics (for example, the longest wavelength of the data area is 2.66 μm, the shortest wavelength is 0.67 μm, and the pilot area is , The longest wavelength of 24 μm and the shortest wavelength of 2 μm).

  On the other hand, a new home digital VTR standard (hereinafter, referred to as DVC) was proposed in July 1993, and is being studied at the HD Digital VCR Conference (for example, see Non-Patent Document 2).

  The DVC is also a standard premised on overwrite recording using only a recording head. A pilot signal for detecting a recording track position is generated by a digital modulation circuit in a data pattern, and recorded as a continuous signal in all track areas.

  Therefore, the following wavelengths are overwritten, and the short wavelength and the long wavelength are overwritten compared to the DAT (the shortest wavelength of data is 0.49 μm and the longest wavelength of a pilot signal is 22.1 μm).

Therefore, in the DVC, only a vapor-deposited tape which is easy to obtain an overwrite characteristic is used.
The DAT Conference Standard Digital Audio Taperecorder System; The DAT Conference, May.29,1987 The role of storage and high density technology in the multimedia age, Yamamitsu et al., The Japan Society of Applied Magnetics, 83rd meeting, 1993.1.25 No6

  If the coating type tape is designed to have a magnetic layer thickness of 0.2 μm or less, the overwriting characteristics can be considerably improved even with the coating type tape, but it is difficult to improve the overwriting characteristics to the same level as the overwriting characteristics of the evaporation tape. In DVC, overwrite characteristics were insufficient for using coated tape.

  Also, if the thickness of the magnetic layer of the coating type tape is designed to be 0.2 μm or less, and a structure in which the overwrite characteristics are easily obtained as much as possible, there is a problem that the output of the low frequency band is reduced as compared with the evaporation tape. .

  Therefore, when an equalizer (hereinafter referred to as EQ) circuit for correcting frequency characteristics used when detecting a reproduced digital signal as digital data uses two types of a vapor deposition tape and a coating type tape, it is not optimized and a detection error is not obtained. There was a problem to increase.

  Also, in a device that adds a low-frequency pilot signal for detecting a recorded track position together with a digital signal, the reproduced pilot signal output differs when using two types of evaporation tape and coating type tape. However, there has been a problem that it is difficult to accurately control the position of the magnetic head to the recorded track position.

  In order to solve the above-mentioned conventional problems, a magnetic recording / reproducing apparatus for a digital signal according to the present invention comprises a recording amplifier for amplifying an input digital signal, a reproduction signal level having a frequency corresponding to the shortest recording wavelength of the digital signal to be recorded. A recording current setting circuit for setting the output current of the recording amplifier to a range larger by 1 dB or more than the recording current value at which the maximum value is obtained, a magnetic head to which the output of the recording current setting circuit is supplied, and the magnetic head, This is a configuration in which recording is performed on a coating type tape having a magnetic layer thickness of 0.2 μm or less, which compensates for overwrite characteristics comparable to a vapor-deposited tape.

  A digital signal magnetic recording / reproducing apparatus according to the present invention comprises a digital modulation circuit for adding a low-frequency pilot signal for detecting a recording track position to an input digital signal, and a recording amplifier for amplifying an output of the digital modulation circuit. A recording current setting circuit for setting an output current of the recording amplifier to a range larger by 1 dB or more than a recording current value at which a reproduction signal level at a frequency corresponding to the shortest recording wavelength of a digital signal to be recorded is maximum; The magnetic head to which the output of the circuit is supplied, and the above-mentioned magnetic head is used to record on a vapor deposition tape or a coating type tape having a magnetic layer thickness of 0.2 μm or less. A reproducing amplifier for amplifying a reproduced signal reproduced from a mold tape through the magnetic head to a predetermined level; And a switching circuit for switching the output of the deposition tape EQ circuit and the coating tape EQ circuit in accordance with the output from the tape type detection circuit. , And the detection error can be minimized even when two types of the evaporation tape and the coating type tape are used.

  The digital signal magnetic recording / reproducing apparatus of the present invention further comprises a digital modulation circuit for adding a low frequency pilot signal for detecting a recording track position to the input digital signal, and a recording circuit for amplifying an output of the digital modulation circuit. An amplifier; a recording current setting circuit for setting an output current of the recording amplifier to a range larger by 1 dB or more than a recording current value at which a reproduction signal level at a frequency corresponding to the shortest recording wavelength of a digital signal to be recorded is maximum; A magnetic head to which the output of the setting circuit is supplied, and using the magnetic head, a vapor deposition tape, or a magnetic layer having a thickness of 0.2 μm or less, is recorded on two types of tapes, the vapor deposition tape, or A reproduction amplifier for amplifying a reproduction signal reproduced from the coating tape through the magnetic head to a predetermined level; A recorded track position is detected from a low frequency pilot signal included in the amplifier output, the magnetic head position is controlled to the recorded track position, and the amplification degree of the control loop is switched according to the output from the tape type detection circuit. It is composed of a control circuit and can control the position of the magnetic head accurately to the recorded track position at the time of reproduction even when two types of the evaporation tape and the coating type tape are used.

  In the digital signal magnetic recording / reproducing apparatus of the present invention constituted by using the above-mentioned means, the recording current setting circuit allows the reproduction signal level at the frequency corresponding to the shortest recording wavelength of the digital signal to be 1 dB or more from the recording current value at which the reproduction signal level becomes maximum. Since the output current of the recording amplifier is set to a large range, the magnetic layer thickness can be compensated for as much as a vapor deposition tape, or the overwrite characteristics of a coating type tape less than the vapor deposition tape can be compensated for as much as a vapor deposition tape.

  Further, the digital signal magnetic recording / reproducing apparatus of the present invention has two EQ circuits corresponding to two types of a vapor deposition tape and a coating type tape, and selects and outputs the two EQ circuit outputs by a switching circuit. Because of the configuration, even when two types of the evaporation tape and the application type tape are used, the detection error can be minimized.

  In the digital signal magnetic recording / reproducing apparatus of the present invention, the amplification degree of the tracking control circuit is switched in correspondence with the deposition tape and the coating tape, so that the two types of the deposition tape and the coating tape can be used. Even in this case, it is possible to accurately control the recorded track position during reproduction.

  Hereinafter, the best mode for carrying out the digital signal magnetic recording / reproducing apparatus of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram of a main part of a digital signal magnetic recording / reproducing apparatus according to the present invention.

  A digital signal obtained by encoding image information, audio information, information communication data, and the like is input from a terminal 1.

  Next, a low frequency pilot signal for detecting a recording track position is added to the digital signal by the digital modulation circuit 2.

  In the DVC, the pilot signal (frequency: 1 / 90T, recording wavelength: 22.1 μm) shown in FIG. 8 is continuously generated using a digital pattern by using the 24-25 modulation rule for digital modulation.

  Here, compared with DAT, the reason that DVC uses a continuous signal with a long wavelength as a pilot signal is to perform control more accurately and more stably at the recorded track position.

  Returning to FIG. 1, the recording amplifier 3 amplifies the input output of the digital modulation circuit 2.

  Next, the recording current setting circuit 4 sets the output current of the recording amplifier 3 to a range larger than the recording current value at which the reproduction signal level of the frequency corresponding to the shortest recording wavelength of the digital signal to be recorded becomes maximum by 1 dB or more. The recording is performed on the coating type tape or the vapor deposition tape 6 through 5.

  Here, the reason why the recording current is set by the recording current setting circuit 4 as described above will be described.

  FIG. 2 shows an example of recording current vs. output, FIG. 3 shows an example of recording current vs. erasing rate in a coating type tape, and FIG. 4 shows an example of magnetic layer thickness vs. erasing rate in a coating type tape. FIG. 5 shows a general structure of a magnetic tape.

  However, the output of FIG. 2 is obtained by measuring the output at the shortest wavelength of 0.49 μm according to the DVC, and the erasure rate of FIGS. 3 and 4 is obtained by recording the signal of the long wavelength of 22.1 μm according to the DVC. A signal having the shortest wavelength of 0.49 μm is superimposed and recorded, and at the time of reproduction, the attenuation of the signal output of the long wavelength of 22.1 μm, that is, the erasing rate (overwrite characteristic) is measured.

  The magnetic tape has the structure shown in FIG. 5, and the thickness δ of the magnetic layer of the vapor-deposited tape used for DVC is about 0.2 μm.

  Here, if the erasure rate is measured by changing the magnetic layer thickness δ of the coating type tape, the characteristics shown in FIG. 4 can be obtained. It can be seen that the overwrite characteristics are improved.

  That is, the recording area of the magnetic tape is determined for each wavelength, and the recording depth is proportional to λ / 4 of the wavelength λ.

  Therefore, considering the shortest wavelength (0.49 μm for DVC), if the magnetic layer thickness is set to 0.2 μm or less, the entire magnetic layer thickness will be recorded at the shortest wavelength, and the overwrite characteristics at long wavelengths will be improved. Is done.

  Therefore, the coating type tape 6 shown in FIG. 1 has a structure in which the thickness of the magnetic layer is 0.2 μm or less.

  Next, as shown in FIG. 2, when a conventional coating type tape (magnetic layer thickness: about 2 μm) is used, the recording current shows a peak at a certain value, and the recording current is increased when the recording current is increased beyond the certain value. The output decreases due to demagnetization.

  However, in the case of a coating type tape in which the magnetic layer thickness δ is set to 0.2 μm or less, the characteristics shown in FIG. 2 are obtained. The attenuation is only about several dB.

  Therefore, the recording current can be set freely within a relatively large range.

  In addition, as shown in FIG. 3, the erasure rate (overwrite characteristic) is improved by setting the recording current to be large.

  Here, the erasing rate required in the digital signal magnetic recording / reproducing apparatus is, for example, -20 dB or less in the case of DVC.

  This is because, in the case of DVC, if it is -20 dB or more, the low-frequency pilot signal indicating the recorded track position is left unerased, and the recorded track position cannot be accurately controlled, and cannot be practically endured.

  Therefore, as shown in FIG. 3, the recording current is set to a value larger than the recording current value (point A) at which the reproduction signal level of the frequency corresponding to the recording wavelength is maximum by 1 dB (point A ') or more, and there is no practical problem. As a result, the overwrite characteristics comparable to those of a vapor deposition tape are ensured.

  Therefore, by setting the current value of the recording current setting circuit 4 in FIG. 1 to a range that is 1 dB or more larger than the recording current value at which the reproduction signal level at the frequency corresponding to the shortest recording wavelength of the digital signal for recording the digital signal is maximized, Rate (overwrite characteristics) can be obtained.

  Further, a recording current set value according to DVC, that is, a current value +4 dB indicating 90% of the maximum output in DVC and Reference-ME is described as 0 dB in FIG.

  Therefore, the recording current set value according to the DVC matches the recording current setting condition of the coating type tape, and the recording current value of the deposition tape and the coating type tape can be set to the same value.

  Next, the magnetic head 5 shown in FIG. 1 will be described according to the characteristics shown in FIG.

  FIG. 6 is a diagram showing the recording current versus the erasing rate when the saturation magnetic flux density of the material near the magnetic head gap of the magnetic head 5 is changed.

  However, in DVC, since the shortest wavelength is 0.49 μm, in order to compensate for recording, the gap length GL of the magnetic head 5 is set to 0.25 μm or less, which is half of the shortest wavelength, and FIG. Show.

  In DVC, since a signal having a minimum wavelength of 0.49 μm is recorded and reproduced, a coating tape having a holding force of 2000 Oe or more is used.

  Therefore, as shown in FIG. 6, if the saturation magnetic flux density of the material in the vicinity of the gap of the magnetic head 5 shown in FIG. 1 is five times the holding force of the coating type tape (2000 Oe), that is, 1.0 T or more, the recording current increases. On the other hand, the magnetic flux from the magnetic head 5 is not strong, and the erasing rate (overwrite characteristics) cannot be improved.

  Therefore, the saturation magnetic flux density of the material near the gap of the magnetic head 5 shown in FIG. 1 needs to be 1.0 T or more.

  Next, the reproduction system of FIG. 1 will be described.

  A digital signal recorded on a vapor deposition tape or a coating type tape 6 is transmitted to a reproducing amplifier 7 via a magnetic head 5, and the reproducing amplifier 7 amplifies and outputs the reproduced digital signal.

  Here, the low-frequency output changes in proportion to the magnetic layer thickness δ, and the lower the δ, the lower the low-frequency output.

  Further, even if the magnetic layer thickness δ is the same value for the vapor deposition tape and the coating type tape, the output necessarily increases for the vapor deposition tape as shown in the frequency characteristics shown in FIG.

  This is because the output at low frequencies is proportional to the amount of magnetic recording medium per unit area, and the magnetic layer of the coating type tape contains a non-recording medium, such as a binder or an abrasive, as compared with a vapor-deposited tape. Have the same value, the low-frequency output of the coating tape deteriorates.

  Therefore, the output of the reproduction amplifier 7 is input to the EQ circuit 8 for the vapor deposition tape and the EQ circuit 9 for the coating type tape, and the EQ characteristics are optimized for each tape type.

  Next, the switching circuit 10 selects and outputs the output of the EQ circuit optimized for each tape according to the output of the tape type detection circuit 12.

  Therefore, errors in data detection can be minimized after the switching circuit 10 irrespective of the deposition tape or the coating type tape.

  Also, a low frequency pilot signal indicating the track position recorded by the digital modulation circuit 2 is added and recorded.

  Therefore, the signal is reproduced from the reproduction amplifier 7 including the low frequency pilot signal, and the tracking control circuit 11 detects the pilot signal and controls the track position where the pilot signal is recorded.

  Therefore, as described above, since the output value of the low frequency is different between the vapor deposition tape and the coating type tape, the control accuracy is stabilized by switching the control loop gain of the tracking control circuit 11 according to the output of the tape type detection circuit 12. I'm trying.

  However, the tape type detection circuit 12 stores information for determining the tape type in a detection hole added to the cassette and, in the case of DVC, a memory attached to the cassette, and determines the tape type by detecting the information.

  As described above, the digital signal magnetic recording / reproducing apparatus of the present invention improves overwrite characteristics by setting the recording current to be larger than the conventional optimum current value by using a coating type tape having a magnetic layer thickness of 0.2 μm or less. Further, it realizes overwrite characteristics comparable to a vapor-deposited tape, and is useful as a magnetic recording / reproducing apparatus for digital signals corresponding to a coating type tape.

  In addition, when using both a coating type tape and a vapor deposition tape having a magnetic layer thickness of 0.2 μm or less, a low-frequency output difference, which is a problem, is set by a dedicated circuit corresponding to the tape type or a control gain is set. By switching for each type, it is possible to optimize the error rate and the tracking control, so that it can be used as a digital signal magnetic recording / reproducing device that supports two types of tapes: a vapor deposition tape and a coating type tape. Useful.

FIG. 2 is a main block diagram showing the configuration of a digital signal magnetic recording / reproducing apparatus according to a first embodiment of the present invention. Characteristic diagram showing one example of recording current and output of coating type tape and vapor deposition tape Characteristic diagram showing an example of a recording current and an erasing rate of a coating type tape Characteristic diagram showing an example of the magnetic layer thickness and the erasing rate of a coating type tape Structural diagram showing the structure of the magnetic tape Characteristic diagram showing an example of a recording current and an erasing rate of a coating type tape when a condition of a magnetic head is changed. Characteristic diagram showing an example of frequency characteristics of a vapor deposition tape and a coating type tape FIG. 4 is a characteristic diagram showing an example of a frequency characteristic of an output of a digital modulation circuit included in the digital signal magnetic recording / reproducing apparatus according to the first embodiment of the present invention.

Explanation of reference numerals

Reference Signs List 2 digital modulation circuit 3 recording amplifier 4 recording current setting circuit 5 magnetic head 6 evaporation tape or coating type tape 7 reproduction amplifier 8 EQ circuit for evaporation tape 9 EQ circuit for coating type tape 10 switching circuit 11 tracking control circuit 12 tape type Detection circuit

Claims (4)

  A pilot signal having a wavelength of 22.1 μm for detecting a track position of a magnetic tape at the time of reproduction is added to an input digital signal in which image information, audio information, and information communication data are encoded, and the pilot signal is added. A digital signal magnetic recording / reproducing apparatus for recording / reproducing a digital signal at a minimum wavelength of 0.49 μm, comprising: a digital modulation circuit for adding the pilot signal to the input digital signal; and a pilot signal output from the digital modulation circuit. A recording amplifier for amplifying the added digital signal; and a recording current value that is 1 dB or more larger than a recording current value at which a reproduction signal level at a frequency corresponding to the shortest recording wavelength of the digital signal to which the pilot signal amplified by the recording amplifier is added is maximized. Recording current setting for setting the output current value of the recording amplifier to a range A digital signal added with a pilot signal amplified by the recording amplifier at an output current value set by the recording current setting circuit and a magnetic tape having a magnetic layer thickness of 0.2 μm or less via a magnetic head. A magnetic recording / reproducing apparatus for digital signals, wherein writing / recording is enabled.   2. The digital signal magnetic recording / reproducing apparatus according to claim 1, wherein the recording current setting circuit sets the same output current value for two types of a vapor deposition tape and a coating type tape.   The recording current setting circuit outputs the same output current of +4 dB to the two types of the vapor-deposited tape and the coated tape, in which the reproduction signal level at the frequency corresponding to the shortest recording wavelength of the digital signal to be recorded indicates 90% of the maximum output. 3. The magnetic signal recording / reproducing apparatus for digital signals according to claim 2, wherein the value is set to a value. 4. The magnetic head according to claim 1, wherein a material having a saturation magnetic flux density of 1 Tesla (T) or more and a magnetic head gap length of 0.25 [mu] m or less is used. Digital signal magnetic recording and reproducing apparatus.

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