JPH01317207A - Multi-layer recording/reproducing device for digital signal - Google Patents

Abstract

PURPOSE:To improve the recording density of the digital signals with use of a magnetic head having a single type of azimuth by demodulating the digital signals from among the carrier waves which are reproduced by the magnetic head and taken out via plural band pass filter parts. CONSTITUTION:A demodulation part 16 demodulates the digital signals from among the carrier waves which are reproduced by a magnetic head 11 and taken out via plural band pass filter parts 13a-13c. The signals reproduced from a magnetic tape by the head 11 are mixed with plural carrier waves. Then these mixed carrier waves are separated from each other via the parts 13a-13c and these separated carrier waves are modulated by their corresponding digital signals respectively. Therefore the digital signals obtained at recording can be reproduced by demodulation. Thus the digital signal that modulated each carrier wave is reproduced individually. As a result, it is possible to improve the recording density of the digital signal with use of a magnetic head having a single type of azimuth.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a recording and reproducing device that records and reproduces digital signals. The present invention relates to a digital signal multilayer recording and reproducing apparatus that records and reproduces a plurality of digital signals by reproducing the same.

(Prior Art) Digital audio tape recorders are beginning to show signs of becoming popular as devices that can record and play back high-quality audio signals with extremely little deterioration in sound quality. is converted into a digital signal, a carrier wave modulated according to the converted digital signal is recorded on a magnetic tape, and at the time of reproduction, the digital signal is reproduced by demodulating the carrier wave taken out from the magnetic tape by a magnetic head, This digital signal is converted into an audio signal.

In this method, only one type of carrier wave can be recorded on one track, so there is a problem that the recording density of the signal cannot be increased.

Therefore, in video tape recorders and the like that require increased recording density on magnetic tape because it is necessary to record digitized audio signals and image signals on the same magnetic tape, two magnetic heads with different azimuth angles are used. , a two-layer recording configuration is adopted in which one magnetic head records digitized audio signals, and the other magnetic head records image signals.

(Problem to be Solved by the Invention) The method of providing two magnetic heads with different azimuth angles described above requires two kinds of digital signals when the magnetic head for recording an image signal is used for recording a digital signal. This makes it possible to perform recording on a magnetic tape, thereby doubling the recording density on the magnetic tape. However, this method requires 2
Since the azimuth angles of the two magnetic heads must be different from each other and high precision is required in manufacturing, there is a problem that manufacturing costs inevitably increase.

Furthermore, it is difficult to increase the number of magnetic heads to three or more due to the relationship of signal crosstalk between magnetic heads, and it is extremely difficult to further increase the recording density.

The present invention has been made in view of the above problems, and an object thereof is to provide a multilayer recording/reproducing device for digital signals that can increase the recording density of digital signals using a magnetic head having one type of azimuth angle. .

(Means for Solving the Problems) A multilayer recording and reproducing device for digital signals of the present invention records a plurality of carrier waves, each of which is modulated according to a digital signal and has a different frequency from each other, on the same rack. By reproducing carrier waves, the configuration is configured to reproduce multiple digital signals, and also includes a magnetic head that reproduces multiple carrier waves recorded on a track, and a magnetic head that reproduces each carrier wave from the multiple carrier waves reproduced by the magnetic head. The device includes a bandpass filter section that extracts a carrier wave, and a demodulation section that demodulates a digital signal from the carrier wave extracted by the bandpass filter section.

(Operation) Since the signal reproduced from the magnetic tape by the magnetic head is a signal in which a plurality of carrier waves are mixed, the mixed carrier wave is separated into each carrier wave using a band pass filter section. Each of these separated carrier waves is a modulated signal modulated by a corresponding digital signal, so by demodulating these separated carrier waves, the digital signal at the time of recording can be reproduced. be exposed.

(Example) Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the electrical configuration of an embodiment of the present invention.

In the figure, the magnetic head 11 is connected to a common contact C of a changeover switch 21 that changes the connection between recording and reproduction, and the contact C of this changeover switch 21 is led to a preamplifier 12. and preamplifier 1
The output of No. 2 is connected in parallel to three bandpass filters 13a, 13b, and 13c constituting the bandpass filter section 13.

The outputs of the bandpass filters 13a, 13b, 13c are:
Switches 14a and 14b provided correspondingly to each other
, 14c, and these switches 14a, 1
After the outputs of 4b and 14c are connected in parallel, the demodulator 16
guided by. Also, band pass filters 13a, 13
The outputs of b and 13c are also guided to a frequency control section 20, and the output of this frequency control section 20 is guided to a carrier wave generation section 19.

A/D converter that digitizes audio signals (not shown)
The output of the modulating section 18 to which the digital output 18a is guided is guided to the contact a of the changeover switch 21 via the output amplifier 17. The modulator 18 receives the output of the carrier wave generator 19, and the output amplifier 17 receives the output of the frequency controller 20.
output is connected. In addition, the changeover switch 21 has
A control output 21a for controlling switching of the connection of the magnetic hemlock 11 is led. Also, the bandpass filter section 13
Switches 14a, 14 inserted between the demodulator 16 and the demodulator 16
The outputs of the reproduction control unit 15 are connected to each of b and 14c, and the reproduction control unit 15 is provided with an output 15a that indicates the frequency of the carrier wave during reproduction.

Regarding the operation of one embodiment of the present invention having the above configuration,
This will be explained below.

The carrier wave generator 19 is configured to be able to generate three carrier waves with different frequencies, and the frequency controller 2
According to the output of 0, a carrier wave of frequency f, , fl, or f3 is sent to the modulation section 18.

The modulator 18 modulates the carrier wave output by the carrier wave generator 19 according to the digital output 18a, and sends the modulated carrier wave to the output amplifier 17. Due to the modulation at this time, sidebands are generated above and below the carrier wave. Since this sideband band is a decoration, as shown in FIG. The setting is such that f3 E2 = f2 fl > 2 layers w so that they do not overlap each other.

FIG. 3+al to FIG. 3 (C1 is an explanatory diagram showing the state of magnetization in the cross section of the magnetic tape.

An arrow P indicates the relative traveling direction of the magnetic tape 31 with respect to the magnetic head 11, and indicates whether the magnetic tape 31 is completely erased or a new magnetic tape 31 [Fig. 3(a)
], f is used as the frequency of the carrier wave. Figure 3.

(The shaded portion 31b of al indicates the portion of the magnetic tape 31 that is magnetized by this recording.

When a new digital signal is to be recorded on the magnetic tape 31 on which a digital signal has been recorded using a carrier wave of frequency f1, the frequency of fl is used as the frequency of the carrier wave.

Figure 3 (showing the situation when using BL cigarettes, with frequency f
The magnetic head 11 side of the magnetized portion (hatched line 3 l b) by the carrier wave of , is magnetized by the carrier wave of frequency f2.
(Diagonal line 31c). However, the depth of magnetization D2 at this time is
The depth Dl of magnetization caused by the carrier wave f is shallower than the depth Dl of magnetization caused by the carrier wave f, and even after this second recording, the magnetic tape 31
A portion 31b magnetized by the carrier wave f1 remains. This is because the depth of magnetization in the magnetic tape 31 becomes shallower as the carrier wave frequency increases during recording, and the recording current supplied from the output amplifier 17 to the magnetic head 11 is This is because the frequency is reduced by the output of the frequency control section 20 when recording.

Figure 3 (cl is the frequency f after performing the above two recordings)
This shows the state of magnetization when recording is performed using carrier wave No. 3, and since the frequency f3 during this recording is the highest frequency, the magnetized portion remains at the shallowest portion (hatched line 31d). The magnetized part 3 according to the frequency f1
1b, a magnetized portion 31c with a frequency f2, and a magnetized portion 31d with a frequency f3.

As explained above, to record a digital signal, first, a carrier wave of frequency f1 is sent to the modulator 18, and the digital output 18
The carrier wave modulated by a is sent to the magnetic head 11 via the output amplifier 17 and the changeover switch 21, and when performing another recording next time, the frequency f2 is
This is done by sending a carrier wave of frequency f from the carrier wave generating section 19 to the modulating section 1, and then when performing another third recording, the carrier wave generating section 19 sends a carrier wave of frequency f to the modulating section 18.

The data recorded on the magnetic tape 31 as described above is transferred to the magnetic head 1 during playback when the control output 21a connects the contact of the changeover switch 21 to the common contact C.
1, but the data sent out by the magnetic head 11 at this time is detected by the magnetized portions 31b, 31c, 31d.
The signal is a mixture of data indicated by the magnetized portions of the three layers. In other words, with frequency f1 as the center frequency, sideband 5
1, a signal having a center frequency of frequency 12 and a sideband 52, and a signal having a center frequency of frequency f3 and a sideband 53. This signal is guided to a bandpass filter section 13 via a changeover switch 21 and a preamplifier 12.

The three bandpass filters 13a, 13b, 13c in the bandpass filter section 13 have respective center frequencies f, , f2 . f, and has a passband of 2fw, the bandpass filter 13
Since the signal passing through a becomes a sideband 51 having the center frequency f1, a signal corresponding to the magnetized portion 31b appears at the output of the bandpass filter 13a. Similarly, the output of the bandpass filter 13b has a magnetized portion 31.
A signal corresponding to the magnetized portion 31d appears at the output of the bandpass filter 13c.

From the above, if the bandpass filters 13a and 13
If a signal appears in the bandpass filter 13c and no signal appears in the bandpass filter 13c, this indicates that the magnetic tape 31 is not magnetized corresponding to the frequency f3. 31 indicates an erased or new tape.

FIG. 4 is a plan view showing how the magnetic tape 31 is magnetized.

The magnetic tape 31 moves in the direction of arrow B, while the magnetic head 11 that performs recording and reproduction moves in the direction of arrow A (
That is, since the magnetic tape 31 is rotated while being in contact with the magnetic tape 31, the magnetic tape 31 is magnetized in the order of 35a to 35c. Further, a control head 34 for controlling the rotation timing of the magnetic head 11 is provided at one end of the magnetic tape 31 (lower part of FIG. 4).
The control signal 36 is recorded and reproduced. This control head 34 records a control signal 36 on the edge of the magnetic tape 31 when recording is performed using a carrier wave of frequency f, and reads the control signal 36 during other operations. , the timing of rotation of the magnetic head 11 is controlled.

From the above, when recording, first playback is performed by connecting the common contact C of the changeover switch 21 to the contact, and from the state of the output of the bandpass filter section 13 at that time, the frequency control section 20 magnetic tape 31
The state of magnetization is read. As a result of reading, three bandpass filters 13a, 13b,
13c, the frequency control section 20 causes the carrier wave generation section 19 to output a carrier wave with a frequency f, and sets the output amplifier 17 so that the value of the recording current is maximized. . Further, in parallel with the recording by the magnetic head 11, the control head 34 is caused to record the control signal 36.

Further, when a signal appears only at the output of the bandpass filter 13a, the frequency control unit 20 outputs a carrier wave of frequency f2 from the carrier wave generation unit 19, and sets the output amplifier 17 so that the value of the recording current is medium. conduct. Furthermore, when a signal appears only in the outputs of the bandpass filters 13a and 13b, the frequency control unit 20 controls the carrier wave generation unit 19 to set the transmission of the carrier wave of frequency f3 and output the output that minimizes the recording current. Settings for the amplifier 17 are performed. During these operations, the control head 34 outputs the control signal 3.
6, the recording operation on the magnetic tape 31 is performed while controlling the rotation timing of the magnetic head 11.

When signals appear at all of the outputs of the bandpass filters 13a, 13b, and 13C, after erasing the magnetic tape 31 with an erasing head (not shown),
Settings are made by the frequency control unit 20 to enable recording using a carrier wave of frequency f1.

Through the above operations, a digitized audio signal is recorded on the magnetic tape 31.

Next, the operation of reading out digital signals recorded on the magnetic tape 31 will be explained.

The common contact C of the changeover switch 21 is controlled by the control output 21a.
By connecting to the contact point, the output of the magnetic heel 11 is passed through the preamplifier 12 to the bandpass filter section 1.
Make the settings as shown in step 3. The magnetic head 11 is then rotated in accordance with the control signal 36 detected by the control head 34. As explained above, the signal appearing at the output of the magnetic head 11 due to this operation consists of the carrier waves f+ +f2 +f'l and the sidebands 51 to 51 generated as a result of the modulation of these carrier waves.
The signal is a mixture of 53 and 53.

Therefore, a carrier wave having a frequency f modulated according to the digital signal appears at the output of the bandpass filter 13a. Furthermore, the output of the bandpass filter 13b has a frequency f
A carrier wave of frequency f3 appears in the output of the bandpass filter 13c (however, in the case of the magnetic tape 31 on which each carrier wave is not recorded, only the output corresponding to the carrier wave that has already been recorded appears). ).

Channel 1 is the digital signal recorded by the carrier wave of frequency 11, channel 2 is the digital signal corresponding to frequency f2, and channel 3 is the digital signal corresponding to frequency f. When a selection is made, a signal corresponding to this operation is sent to the playback control unit 1 via the output 15a.
5.

When channel 1 is selected, the reproduction control section 15 closes the switch 14a and opens the other switches 14b and 14C according to the output 15a.

Therefore, the carrier wave of frequency 11 is guided to the demodulator 16, and the demodulator 16 outputs a digital signal equivalent to the digital signal used to modulate the carrier wave of frequency f1. This digital signal is connected to a D/
The signal is guided to the A converter, where it is converted into an audio signal and then sent to the outside.

Also, when channel 2 is selected, switch 14
b is closed and switches 1.4a and 14c are opened, so that the carrier wave of frequency f2 is guided to demodulator 16. At this time, the digital signal corresponding to this carrier wave is demodulated by the demodulation section 16, and is sent out as an audio signal via a D/A converter. The same applies when channel 3 is selected.

Note that the present invention is not limited to the above-mentioned embodiments, and although a configuration using three types of carrier wave frequencies has been described, a configuration using carrier waves of four types of frequencies as other arbitrary types of frequencies is also possible. It is possible to do so.

Furthermore, in the above embodiment, a case has been described in which the present invention is applied to an audio recording device that digitizes and records an audio signal, but the present invention can also be applied to an external storage device that stores digital data in a computer or the like. It is possible to apply.

(Effects of the Invention) The multilayer recording and reproducing device for digital signals according to the present invention is configured to record a plurality of carrier waves modulated according to the respective digital signals on the same track, and a magnetic head that performs reproduction from this track. The carrier wave is extracted by guiding the output of the multiple carrier waves to a band pass filter section having a pass band corresponding to the frequency of each carrier wave, and the extracted carrier wave is demodulated by the demodulation section. Since the digital signals that were previously modulated are individually reproduced, it is possible to increase the recording density of digital signals using a magnetic head with one type of azimuth angle.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the electrical configuration of an embodiment of the present invention, FIG. 2 is an explanatory diagram showing the relationship between the frequencies of a plurality of carrier waves, and FIG. 4 is an explanatory diagram showing the state of magnetization in a cross section of the magnetic tape, and FIG. 4 is a plan view showing the state of magnetization of the magnetic tape. 11...Magnetic head 13...Band pass filter section 16...Demodulation Figure 2 Figure 3 (a) Figure 3 (C)

Claims (1)

[Claims] 1) A plurality of digital signals can be reproduced by recording a plurality of carrier waves, each modulated according to a digital signal and having different frequencies on the same track, and reproducing the recorded carrier waves. A recording and reproducing apparatus that performs the following: a magnetic head that reproduces a plurality of carrier waves recorded on the track; a bandpass filter section that extracts each carrier wave from the plurality of carrier waves reproduced by the magnetic head; A multilayer recording and reproducing apparatus for digital signals, comprising a demodulation section that demodulates a digital signal from a carrier wave extracted by the bandpass filter section.