JPH03120602A - Recording and reproducing device for digital signal - Google Patents

Abstract

PURPOSE:To absorb the dispersion of writing characteristics in plural magnetic heads and to eliminate adjustment in a manufacture process by automatically and always adjusting a recording (writing) current for a magnetic recording medium to be an optimum value. CONSTITUTION:A basic frequency component is extracted in BPF 11, and a third higher harmonics component in BPF12. Then, they are detected in detec tion circuits 13 and 14 and are supplied to a subtracter 18, whereby an output signal comes to H1/3. Then, change over switches Sw1 and Sw2 are respectively connected to a subtracter 18-side by a control signal from a recording system signal processing circuit 3 when the signals of heads H3 and H4 are reproduced. The output H1/3 of the subtracter is sample-held in the holding circuits 15 and 16. The signal voltage is compared (subtracted) with a reference level Vref in comparators 20 and 21 and voltages corresponding to compared results (level difference) are respectively supplied to the control terminals of recording amplifiers A1 and A2. Thus, the optimum recording (writing) current can auto matically and always be set by a negative feed back operation even if there is the dispersion of the characteristics in the heads H1, and H2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a digital signal recording and reproducing device particularly suitable for application to a DAT streamer for information equipment.

[Conventional technology]

DAT (Digital Audio) uses magnetic tape as a recording medium to record (record) and play back digital audio signals.
l Audio Tape (Recorder), which is equipped with a pair of recording heads and a pair of reproduction heads,
A digital signal recording and reproducing apparatus that is configured to be able to immediately monitor and reproduce data while recording and that can be applied to a DAT streamer for information equipment has a configuration schematically shown in FIG. In this figure, H and ~H are magnetic heads,
Of these, H, H2 are recording heads, and H3 and HA are reproducing heads. Note that the magnetic heads H1 to H are HI*
The recording heads H1 and H2a and the reproducing head H3 are arranged at equal intervals (rotation angle 90°) on the circumferential surface of one rotating drum (not shown) in the order of H3s H2p H4.
and H4 are arranged at symmetrical positions, and these two pairs of heads alternately apply a rotation angle of 90° to the circumferential surface of the rotating drum.
The apparatus is configured to perform recording and monitor reproduction on a magnetic tape that is tightly wound in parallel with each other. Further, 2 is a recording circuit including a recording amplifier, etc., 3 is a recording system signal processing circuit, 4 is a reproduction circuit including a reproduction amplifier, etc., 5 is a reproduction system signal processing circuit, 6 is a servo block, and 7 is for rotational drive. 8 is a host computer interface block, 29 is a mechanical control CPU, and the host computer 31. and storage tape cassette (
A magnetic tape T is set, which is partially pulled out from a tape (not shown).

In this format on the magnetic tape T, a 1.57 MH
Three blocks (114, 8μ5ec) of the z signal are to be recorded continuously. In addition, in the DAT streamer normally used for information equipment, as mentioned above, while the recording heads HI and H2 record alternately, the playback heads H3 and H& can immediately monitor and reproduce the data, making it possible to check whether the data is being recorded correctly. Monitor screen 3 of host computer 31
It is configured so that judgment can be made based on the number of errors displayed in 2.

[Problem to be solved by the invention]

In the above-mentioned conventional digital signal recording and reproducing apparatus, the recording current is only set at the beginning of recording, and due to variations in the electromagnetic conversion characteristics of the magnetic tape T used and the built-in magnetic heads H, ~H4, etc., the recording current is always set. It is not always possible to obtain optimal records. Furthermore, if the variations in the characteristics of the four magnetic heads are not small, it is necessary to take some countermeasures during manufacturing, but no effective countermeasures have been taken in conventional devices.

[Means to solve the problem]

The digital signal recording and reproducing apparatus of the present invention includes a recording circuit that can vary a recording current according to a control signal, and a reproducing head that outputs a signal of a predetermined frequency from among the signals recorded on a magnetic recording medium by the recording head. While playing,
a sampling pulse generator that generates pulses for sampling the reproduced signal; and a first pulse generator that extracts the fundamental wave component and third harmonic component of the predetermined frequency signal reproduced by the reproduction head, respectively. a second band frame, a wave device; A hold circuit samples and holds a voltage corresponding to the difference in the output of the second bandpass filter using pulses from the sampling pulse generator, and compares the output voltage of the hold circuit with a preset reference voltage. The above-mentioned problem has been solved by comprising a comparator that applies a voltage corresponding to the difference to the control signal terminal of the recording circuit.

〔Example〕

In the case of digital signal recording, unlike analog signal recording, it is written (recorded) using a rectangular wave current without bias, and the recording level is determined by the recording/reproducing level of a signal at a constant frequency or the recording/reproducing level difference between two frequencies. When a signal of a certain frequency is recorded and played back, the difference between the fundamental frequency level and the third harmonic level (hereinafter referred to as "fundamental wave - third harmonic level") "3rd harmonic" is "HH"
) can also be used to evaluate the recording level. FIG. 3 shows a characteristic correlation diagram between the recording current and Hsl. As is clear from this diagram, as the recording current increases, H4 decreases inversely proportionally.
The harmonics increase as the recording current increases.

When the gap length of the magnetic head and the spacing loss distribution are controlled, the recording level on the tape can be evaluated using this HS4. Therefore, if the recording current is set so that H4 is uniform for each head and each tape used, a uniform recording level can be obtained.

The greatest feature of the digital signal recording/reproducing apparatus of the present invention is that the recording current can be automatically set to an optimum value by utilizing the recording current-H14 characteristic.

Hereinafter, specific embodiments of the digital signal recording/reproducing apparatus of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of the main parts of a digital signal recording and reproducing apparatus 10 according to the present invention. In this figure, the same components as those of the conventional apparatus 1 shown in FIG. omitted.

In the figure, A I m A 2 is a recording amplifier, A3 to A5 are playback amplifiers, 9 is an adder, 17 is an equalizer, 11°1
2 has a center frequency of 1.57MHz and 4.7MHz (
13.14 is a detection circuit, 15°16 is a hold circuit, 18 is a subtracter, S town, 8w2 is a changeover switch, and 19 to 21 are comparators.

In the recording mode, the recording head H is moved against the magnetic tape T.
, , H2 alternately record, and the playback heads H3, H
& is immediately played back alternately, amplified by head amplifiers A3 and A4 via a rotary transformer (not shown), synthesized by adder 9, and further supplied to head amplifier A5. After dB amplification, the waveform is equalized by an equalizer 17. The output signal of the equalizer 17 is supplied to the reproduction system signal processing circuit 5 via the comparator 19, and is also supplied to the BPFll and 12. As mentioned above, on the magnetic tape T, 1.
Since a 57 MHz signal is always recorded, the BPFil extracts its fundamental frequency component, and the BPF 12 extracts its third harmonic component, which are respectively detected by the detection circuits 13 and 14, and then connected to the positive input terminal of the subtracter 18. and the negative input terminal, respectively. Therefore, the output signal of the subtracter 18 is the fundamental wave -
This becomes the third harmonic, that is, HyJ, and based on this, a control signal is generated in the following manner.

The changeover switches Swl and 8w2 switch the 1.57 MHz signals of the A-Chf head H3) and B-ch (head Ha), respectively, in response to control signals as shown in FIG. 4(B) and FC) from the recording system signal processing circuit 3. During reproduction (see FA in the same figure), it is connected to the subtracter 18 side. That is, the recording system signal processing circuit 3 has a built-in sampling pulse generator. As a result, the subtracter outputs H1 and S are sampled and held in the hold circuits 15 and 16. The thus held signal voltages are passed through comparators 20 and 2, respectively.
1, the voltage is compared (subtracted) with the reference level Vref, and the voltage corresponding to the comparison result (level difference) is applied to each recording amplifier A I.
+A Supplies to the control terminal of 2. That is, these output voltages become recording current control signals for A-ch (head H+) and B-ch (head H2), respectively, and head H
Even if there are variations in characteristics between I pH and H2,
The feedback (negative feedback) operation with the above configuration automatically sets the optimum recording (writing) current at all times.

〔effect〕

As explained in detail above, according to the digital signal recording/reproducing apparatus of the present invention, recording (writing) on a magnetic recording medium is possible.
Since the current can be automatically adjusted to the maximum fl value at all times, it is possible to absorb variations in the writing characteristics of multiple magnetic heads, eliminating the need for adjustments during the manufacturing process, and also absorbing variations in the recording characteristics of the magnetic recording media used. Therefore, it has the advantage that it is possible to realize the optimum recording current setting for each medium.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the main parts of the digital signal recording and reproducing device of the present invention, FIG. 2 is a basic configuration diagram of the digital signal recording and reproducing device that can be used for a 4ch D^■ streamer, and FIG.
The figure is a characteristic correlation diagram between recording current and HH, and FIG. 4 is a signal waveform diagram (timing chart) for explaining the operation of the main components of the apparatus of the present invention. 2... Recording circuit section, 3... Recording system signal processing circuit, 5.
...Reproduction system signal processing circuit, 9...Adder, 10...
Digital signal recording and reproducing device, 11.12...BPF
, 13.14...Detection circuit, 15.16...Hold circuit, 17...Equalizer, 18...Subtractor, 1
9 to 21... Comparator, A I # A 2...
・Recording amplifier, A3-A5... Playback amplifier, H1-H
4... Magnetic head, Swl, 8w2... Changeover switch, T... Magnetic tape.

Claims (1)

[Scope of Claims] A digital signal recording and reproducing apparatus that includes a pair of recording heads and a pair of reproducing heads and is configured to record and simultaneously monitor and reproduce a recording circuit that can vary a recording current according to a control signal. , a sampling pulse generator that generates a pulse for sampling the reproduced signal when the reproduction head reproduces a signal of a predetermined frequency from among the signals recorded on the magnetic recording medium by the recording head; first and second bandpass filters for respectively extracting a fundamental wave component and a third harmonic component of the predetermined frequency signal reproduced by the reproduction head; A hold circuit that samples and holds a voltage corresponding to the difference in output using a pulse from the sampling pulse generator, and a hold circuit that compares the output voltage of the hold circuit with a preset reference voltage and outputs a voltage corresponding to the difference as described above. 1. A digital signal recording and reproducing device comprising: a comparator that applies a signal to a control signal terminal of a recording circuit.