JPH0380401A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To stably demodulate a PCM signal even when the characteristic of a 1st magnetic head group disperses and to keep the disturbance to a video system to the necessary minimum by providing a 3rd magnetic head group which reproduces the PCM signal after overwriting is performed with a video signal. CONSTITUTION:A rotating cylinder is provided with the 1st, the 2nd and the 3rd magnetic head groups 57, 63 and 67. The 2nd magnetic head group 63 can record a signal on a magnetic tape 64 previous to the 1st magnetic head group 57, which can overwrite and record a different signal on a track where the signal is recorded by the 2nd magnetic head group 63. The 3rd magnetic head group 67 reproduces the PCM signal which is attenuated because the video signal is overwritten by the 1st magnetic head group 57. The signal reproduced by the 3rd magnetic head group 67 is given to a level detector 70 through an amplifier 69 and the value of a current which flows in the 1st magnetic head group 57 is controlled by a control unit 71 based on the signal.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a video tape recorder for recording and reproducing video signals and the like.

Prior Art In recent years, video tape recorders (hereinafter referred to as VTRs)
There is a trend toward higher image quality. Regarding audio signal recording, progress is being made in the development of systems capable of recording pulse code modified 111 (hereinafter referred to as PCM) signals, typified by compact discs and digital audio recorders.

For example, there is a magnetic recording/reproducing device described in Japanese Patent Application Laid-Open No. 61-294663.

A conventional magnetic recording/reproducing device will be explained below.

FIG. 3 is a block diagram of a conventional magnetic recording/reproducing device.

Figures 4 (a) and (b) are spectrum diagrams of signals recorded on magnetic tape, and Figure 5 shows the recording characteristics of signals recorded and reproduced by the first magnetic head group in Figure 3 and the second magnetic head. FIG. 3 is a diagram showing the erasure rate of a signal (PCM signal) recorded by a head group. In FIG. 3, 1 is a 14th input terminal into which a video signal is input; 2 is a modulator that modulates the video signal input to the first input terminal 1 into a signal recordable on the magnetic tape 15; A first magnetic head group 7a 3 amplifies the output signal of the modulator 2 and is attached to a rotating cylinder 6 via a first switch 4 and a first rotating transformer 5.

7b, 8 is the second input terminal into which the audio signal is input, and ``9'' is the audio signal input to the second input terminal 8, after converting it into a digital signal,
A first signal processor that performs various signal processing; 10 is a ○-QPSK modulator for performing offset four-phase phase shift 11 (hereinafter referred to as 0-QPSK) on the output signal of the first signal processor 9; 11 is for amplifying the output signal of the 0-QPSK modulator 10 and supplying it to the second magnetic head group 14a, 14b attached to the rotary cylinder 6 via the second switch 12 and the second rotary transformer 13. second amplifier, 15
1 is a magnetic tape, 16ai6b is a guide post, and 17 is an adverb device that controls the rotation of the rotating cylinder 60 and the running of the magnetic tape 15. 18 is the first magnetic head group 7a, 7
a third amplifier 19 demodulates the output signal of the third amplifier 18 into a video signal and amplifies the signal reproduced by The demodulator 21 outputting to the output terminal 20 of 1 is reproduced by the second magnetic head group 14a, 14b,
A fourth amplifier 22 amplifies the signal supplied via the M2 rotary transformer 13 and the second switch 12;
23 is a 0-QPSK demodulator that demodulates the output signal of the EQ 22 into a digital signal, and 24 is the output of the ○-QPSK demodulator 23. This is a second signal processor that performs various signal processing on the signal and returns it to the original audio signal, and then outputs the signal to the second output terminal 25.

The operation of the conventional magnetic recording/reproducing apparatus configured as described above will be described below.

The video signal input to the first input terminal 1 is separated into a luminance signal and a chrominance signal by a modulator 2, and then subjected to frequency modulation and low frequency conversion. The frequency modulated luminance signal and the low frequency converted color signal are added and supplied to the first amplifier 3.

The signal amplified by the first amplifier 3 is passed through the first switch 4 switched to the R side and the first rotary transformer 5 to the first magnet with an azimuth angle of ±6° attached to the rotary cylinder 6. It is added to head groups 7a and 7b. The audio signal input to the second input terminal 8 is converted into a digital signal by the first signal processor 9, and then subjected to signal processing such as addition of an error correction code and formatting ink. and,
The signal is output to the 0-QPSK modulator 10 as a digital signal of approximately 2.6 Mbps. The 0-QPSK modulator 10 O-QPSK modulates the output signal of the first signal processor 9 into the spectrum band shown in FIG. Second amplifier 11
The signal amplified by added to.

A magnetic tape 15 is wound diagonally around the rotating cylinder 6 by guide pins 16a and 16b, and runs in the direction of arrow B shown in FIG. At the same time, the rotating cylinder 6 is controlled by the control device 17 and rotates in the six directions of the arrows. The second magnetic head group 14a, 14b is the first magnetic head group 7a,
It is attached to the rotating cylinder 6 so that signals can be recorded on the magnetic tape 15 prior to the magnetic tape 7b. Therefore - 烙2
The first magnetic head groups 7a, 7b record signals on the tracks on which the first magnetic head groups 14a, 14b have recorded signals.

Next, the playback operation will be described. Although the tracks recorded on the magnetic tape 15 overlap each other, the azimuth angles of the magnetic heads are different, so that signals recorded at different azimuths are attenuated due to azimuth loss during reproduction. First magnetic head details 7a.

The signal regenerated at 7b is applied to the third amplifier 18 via the first rotary transformer 5 and the first switch 4 switched to the P side. The signal amplified by the third amplifier 18 is demodulated into a video signal by the demodulator 19 and sent to the first output terminal 2.
Output to 0. The signals reproduced by the second magnetic head group 14a, 14b are transferred to the fourth
The signal is applied to the amplifier 21 and amplified. Signals reproduced from the second magnetic head group 14a, 14b (PCM signal)
is overwritten from above by the first magnetic head group 7a, 7b, so it is about 16d as shown in
B The output is attenuated. The frequency characteristics of the EQ 22 are set in advance so that the frequency characteristics are flat in the recording/reproducing system. The signal amplified by the fourth amplifier 21 has its frequency characteristics corrected by the EQ 22, and then is demodulated into a digital signal by the 0-QPSK demodulator 23. Second signal processing Jt24
demodulates this digital signal to the original audio signal and outputs the audio signal to the second output terminal 25.

Problem to be Solved by the Invention However, in the above configuration, the first magnetic head group 7a
, 7b, the erase rate of the PCM signal may differ even if the gain of the third amplifier 18 is constant and the current flowing through the first magnetic head group 7a, 7b is constant. A phenomenon occurs. Furthermore, when the first magnetic head group 7a, 7b is used for a long time, the gap dibs of the heads become shorter, the intensity of leakage magnetic flux from the gap changes, and the erase rate of the PCM signal changes. Therefore,
There were problems in that the error rate during demodulation worsened, making it difficult to demodulate the PCM signal, and the erasure rate of the PCM signal was too low, leaking into the video system and causing deterioration of the video S/H. .

The present invention solves the above-mentioned conventional problems, and aims to stably demodulate PCM signals even if the characteristics of the first magnetic head group 7a, 7b vary, and to minimize interference to the video system. The purpose of the present invention is to provide a magnetic recording/reproducing device that enables the following.

Means for Solving the Problems In order to achieve this object, the magnetic recording/reproducing device of the present invention has a first magnetic head group attached to a rotating cylinder, and a first magnetic head group that is different from the first magnetic head group and is identical to the first magnetic head group. A second and third magnetic head group having an azimuth angle, a first modulator that modulates the input video signal, and a modulated input audio signal that is digitized and supplied to the second magnetic head group. a level detector that outputs a voltage proportional to the amplitude of the reproduced signal from the third magnetic head group; amplify the output signal of the first
an amplifier that supplies the output signal of the level detector to a group of magnetic heads; if the output level is greater than a predetermined value, the amplification factor of the amplifier is increased; if the input is smaller than the predetermined value, the amplification factor of the amplifier is increased; It has a configuration including a controller that lowers the @ rate.

Function The present invention uses the second magnetic head group to operate the PC with the above-described configuration.
A first magnetic head group overrides and records a video signal on the track where the M signal is recorded. Then, the PC that was attenuated because it was overridden by the first magnetic head group
The third magnetic head group reproduces the M signal, and the reproduction signal tli! A level detector outputs a voltage proportional to the width to the controller. The controller controls the gain of the amplifier that supplies recording signals to the first magnetic head group so that the output signal of the level detector becomes a predetermined value.

As a result of the above, even if the characteristics of the first magnetic head group vary, the reproduction signal forward width value of the PCM signal can always be fixed to a predetermined value. Therefore, the stable fMI of the PCM signal
J@ is possible, and interference to the video system can be suppressed to the necessary minimum.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a magnetic recording/reproducing apparatus according to an embodiment of the present invention. FIG. 2 is a track pattern diagram of a magnetic tape recorded by the magnetic recording/reproducing apparatus of the embodiment.

In FIG. 1, 51 is a first input terminal into which a video signal is input; 52 is a modulator that modulates the video signal input to the first input terminal 51 into a signal recordable on a magnetic tape 64;
53 is a first amplifier that amplifies the output signal of the modulator 52. The first amplifier 53 is provided with a gain control terminal, and the output signal is connected to the rotary cylinder 56 via a switch 54 and a first rotary transformer 55 and has a first azimuth angle, for example, a first azimuth angle of ±60°. Magnetic head details 57
a, 57b. 58 is a second input terminal into which an audio signal is input; 59 is a first signal processor that performs various signal processing after converting the audio signal input to the second input terminal 58 into a digital signal; and 60 is a first signal processor that performs various signal processing. First signal processor 5
9 output signal is offset 4-phase phase modulation (hereinafter referred to as 0-Q
0-QPSK modulator for (referred to as PSK), 61
amplifies the output signal of the 0-QPSK modulator 60, and connects the second magnetic head group 63a, which is attached to the rotary cylinder 56 via a second rotary transformer 62 and has a second azimuth angle, for example, ±20'' azimuth angle. , 63b; 64 is a magnetic tape; 65a;

65b is a guide post, and 66 is a control device that controls the rotation of the rotary cylinder 56 and the running of the magnetic tape 64.

67a and 67b are third magnetic heads having a second azimuth angle for reproducing the signals recorded by the second magnetic head group 63a and 63b.
magnetic head group 69 is a third magnetic head group 63a, 6
a third amplifier that amplifies the signal regenerated by 3b and supplied through a third rotary transformer; 70 a level detector that outputs a voltage proportional to the amplitude of the output signal of the third amplifier 69; 71 is a controller that controls the gain of the first amplifier 53 according to the output voltage of the level detector 70; 72 is a third controller;
EQ, 7 for enhancing the high frequency components of the output signal of the amplifier 69;
3 demodulates the output signal of EQ72 into a digital signal 0
-QPSK demodulator, 74 is 0-QPSK 1M
This is a second signal processor that performs various signal processing on the output signal of the modulator 73 and returns it to the original audio signal, and then outputs the signal to the first output terminal 75. A fourth amplifier 76 amplifies the signal reproduced by the first magnetic head group 57a, 57b and supplied via the first rotary transformer 55 and switch 54;
A demodulator 77 demodulates the output signal of the fourth amplifier 76 into a video signal and outputs it to the second output terminal 78.

The operation of the magnetic recording/reproducing apparatus in this embodiment configured as above will be described below.

The video signal input to the first input terminal 61 is transmitted to the modulator 52
After the signal is separated into a luminance signal and a chrominance signal, each signal is subjected to frequency modulation and low frequency conversion. The frequency modulated luminance signal and the low frequency converted color signal are added and supplied to the first amplifier 53. The signal amplified by the first amplifier 53 is transferred to the switch 54 switched to the R side and the first rotary transformer 55.
The magnetic head is applied to a first group of magnetic heads 57a, 57b with an azimuth angle of ±6° attached to a rotary cylinder 56 via the magnetic head.

The audio signal input to the second input terminal 58 is converted into a digital signal by the first signal processor 59, and then subjected to signal processing such as addition of an error correction code and formatting ink. Then, approximately 2.6 Mbp is sent to the 0-QPSK modulator 60.
It is supplied as a digital signal of s. 0-QPSKf
The li device 60 converts the output signal of the first signal processor 59 into 2.5
0-Q in the spectral band shown in Figure 4 with the carrier wave of MH2.
PSK modulated and supplied to the second amplifier 61. The signal amplified by the second amplifier 61 is transferred to the second rotary transformer 62.
A second magnetic head group 63a with an azimuth angle of ±20° is attached to the rotating cylinder 56 via.

63b.

A magnetic tape 64 is obliquely wound around the rotating cylinder 56 by guide bins 65a and 65b, and runs in the direction of arrow B shown in FIG. At the same time, the rotating cylinder 56 is controlled by the control device 66 and rotates in the six directions of arrows. Second magnetic head group 63a.

Reference numeral 63b indicates that signals can be recorded on the magnetic tape 64 in advance of the first magnetic heads 57a and 57b, and the second magnetic heads 63a and 63b can record signals on the tracks on which the signals have been recorded on the first magnetic head group 57a. , 57b can override record different signals.
a, 57b and the second magnetic head 63a.

63b are attached to the rotating cylinder 56 at different heights and at different positions.

Figure 2 shows this situation. In FIG. 2, C indicates the track of the PCM signal recorded by one of the magnetic heads of the second magnetic head group 63a, 63b, and D indicates the track of the PCM signal recorded by one of the magnetic heads of the first magnetic head group 57a, 57b. This is a track of video signals recorded by a magnetic head.

Further, the third magnetic head group 67a, 67b having the same azimuth angle as the second magnetic head group 63a, 63b is located behind the first magnetic head group 57a, 57b, and 63a and 63bhf are attached to the rotating cylinder 56 so as to run on the recorded tracks. Therefore, the third magnetic head group 67a, 67b is the second magnetic head group 63a.

After recording by the magnetic head 63b, the first magnetic head group 57a.

57b, the attenuated PCM signal is reproduced because the video signal is overridden.

The signals reproduced by the third magnetic head group 67a, 67b are applied to a third amplifier 69 via a third rotary transformer 68. The level detector 70 outputs a voltage proportional to the Wi width of the output signal of the third amplifier 69 to the controller 71.

When the output voltage of the level detector 70 is higher than a predetermined voltage, the controller 71 controls the gain of the first amplifier 53 because the erasure rate of the PCM signal is lower than the lowest level at which the PCM signal can be stably demodulated. is increased, the tiJllE value flowing through the first magnetic head group 57a, 57b is increased, and the erasure rate is increased. Conversely, if the output voltage level of the level detector 70 is smaller than the predetermined value, the erasure rate of the PCM signal is higher than the lowest level at which the PCM signal can be stably demodulated, so the gain of the first amplifier 53 is reduced and the The current value flowing through the first magnetic head group 57a, 57b is reduced to reduce the erasing rate.

As a result of the above, the playback output of the PCM signal may vary due to variations in the components and structure of the first magnetic head group 57a, 57b, or due to the first magnetic head being used for a long time, the gap dibs of the head may become short. Even if the recording efficiency changes due to a change in the intensity of leakage magnetic flux from the PCM signal, the PCM signal can be fixed at the lowest level at which 0-QPSK demodulation can be performed stably.

Furthermore, since the tracks recorded on the magnetic tape 64 overlap each other, the azimuth angles of the magnetic heads are different and the PCM signal is attenuated by 'A' due to the azimuth loss. A phenomenon that causes S/N deterioration occurs. However, since the recording and playback level of the PCM signal can be minimized, the video S
/N deterioration can also be minimized.

Next, the playback operation will be described. First magnetic head group 57
The signals reproduced by a and 57b are transferred to the first rotary transformer 55.
and is applied to the fourth amplifier 76 via the switch 54 switched to the P side. The signal amplified by the fourth amplifier 76 is converted into a video signal fj! by a fiJlill device 77. ! i
t and output to the second output terminal 78. The signals reproduced by the third magnetic head group 67a, 67b are transmitted to the third magnetic head group 67a, 67b.
The signal is applied to a third amplifier 69 via a rotary transformer 68 and is amplified. Third magnetic head group 67a, 67
The signal (PCM signal) reproduced from b is sent to the first magnetic head group 57a.

57b, the video signal is overwritten and recorded from above, so it has a frequency characteristic in which the high frequency range is attenuated. EQ
72 is a recording/reproducing system whose frequency characteristics are set in advance so that the frequency characteristics are flat. After the frequency characteristics of the signal amplified by the third amplifier 69 are corrected by the EQ 72,
The signal is demodulated into a digital signal by a 0-QPSK full unit 73. The second signal processor 74 demodulates this digital signal into the original audio signal and outputs the audio signal to the first output terminal 75.

As described above, according to this embodiment, the third magnetic head group reproduces the PCM signal after being overridden with the video signal, and the voltage value proportional to the layer width of the PCM signal reproduced from the magnetic head is provided. By providing a level detector that outputs a recording signal and a controller that controls the gain of an amplifier that supplies a recording signal to the first magnetic head group so that the output signal from the level detector has a predetermined voltage value, Even if the characteristics of the first magnetic head group vary, the width of the reproducing layer for PCM signals can always be fixed at a predetermined value, and stable f of PCM signals can be maintained.
Enables I key. Furthermore, it becomes possible to suppress interference to the video system to the necessary minimum.

In this embodiment, in the reproduction state, the PCM signal is reproduced by the third magnetic head group 67a, 67b, but it may be reproduced by the second magnetic head group 63a, 63b.

Effects of the Invention As described above, the present invention provides a magnetic head group for reproducing a PCM signal after being overridden with a video signal, and a voltage value proportional to the layer width of the PCM signal reproduced by the magnetic head group. The video signal can be recorded by providing a level detector that outputs the signal and a controller that controls the gain of the amplifier that supplies the recording signal to the magnetic head group so that the output signal from the level detector has a predetermined voltage value. Even if the characteristics of a group of magnetic heads vary, the reproduction amplitude of the PCM signal can always be fixed at a predetermined value, and stable iam of the PCM signal is possible. Furthermore, it becomes possible to suppress interference to the image system to the necessary minimum.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a magnetic recording/reproducing apparatus according to an embodiment of the present invention, Fig. 2 is a track pattern diagram of a magnetic tape, Fig. 3 is a block diagram of a conventional magnetic recording/reproducing apparatus, and Fig. 4 is a block diagram of a magnetic tape. FIG. 5 is a diagram showing the recording characteristics of the signal recorded and reproduced by the first magnetic head group and the erasure rate of the signal (PCM signal) recorded in g2 by the second magnetic head group. . 51.58...Input terminal, 52...Modulator,
53.61.69.76...Amplifier, 54...
Switch, 55.62.68...Rotating transformer,
56... Rotating cylinder % 57a, 57b, 63
a. 63b, 67a, 67b”-input terminal, 59.74
...Signal processor, 60...0-QPSK modulator, 64...Magnetic tape, 65a, 65b...Guide post, 66...Control device, 70...
Level detector, 71...Controller, 72...
Equalizer, 73...0-QPSKflli device,
77... Demodulator.

Claims (1)

[Scope of Claims] A first magnetic head group having a first azimuth angle attached to a rotating cylinder; and a first magnetic head group attached at a different position from the first magnetic head group; a second magnetic head group having different azimuth angles, and a third magnetic head group installed at a different position from the first and second magnetic head groups and having the same azimuth angle as the second magnetic head group. a first modulator that modulates an input video signal, a signal processor that digitizes, encodes and formats the input audio signal, and an output of the signal processor. a second modulator that modulates a signal and supplies it to the second magnetic head group; a level detector that outputs a voltage proportional to the amplitude of the reproduced signal reproduced by the third magnetic head group; an amplifier that amplifies the output signal of the first modulator and supplies it to the first magnetic head group by changing the amplification factor according to a control signal given from the outside; and an amplifier that receives the output signal of the level detector as input; a controller that increases the amplification factor of the amplifier when the output level is larger than a predetermined value and decreases the amplification factor of the amplifier when the input is smaller than the predetermined value; and a signal reproduced by the first magnetic head group. a first demodulator that demodulates the signal into a video signal; and a second demodulator that demodulates the signal reproduced by the second magnetic head group or the third magnetic head group into an audio signal. A magnetic recording/reproducing device characterized by: