JPH0229902A - Digital magnetic recording and reproducing device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a multi-herd digital magnetic recording restraint device for highly reliable recording of video, audio and data, for example for commercial use.

BACKGROUND OF THE INVENTION Conventional override erasure is commonly used in digital magnetic recording and reproduction. The main reason for this was that the deterioration of reproduced signals due to residual signals, which is seen in analog systems, is not as noticeable, so a dedicated head for erasing can be omitted.

For example, in a digital audio tape recorder (hereinafter referred to as DAT), an optimal recording current is passed through the head so that the magnetization depth of the tape magnetic surface is approximately constant in the frequency range that includes the shortest and longest recording wavelengths. It allows override deletion.

This will be explained below with reference to FIG. FIG. 4 is an example of the relationship between the recording current to the head and the output level during reproduction, where the dotted line indicates the recording wavelength λ=130 μm, and the solid line indicates 72
This is a characteristic curve for the case of 0.7 μm. The recording current and relative playback output have a wider linear range when the frequency is low.
When the frequency is high, the linear range becomes narrow and reaches a maximum at point B. The optimum recording current is set near this maximum value point B.

At this time, the frequency characteristics of the relative reproduction output become approximately the best within a predetermined range. In addition, the respective magnetization patterns at points A, B, C, D, and H plotted on the characteristic curve in Figure 4 are shown in Figure 6 (a), (b), (C), (d
), (e). In FIG. 5, a fractured surface perpendicular to the head gap is shown to view the depth direction of the magnetic surface. At point B, which is the maximum value, the magnetization depth is approximately λ/
It becomes 4. It can be seen that the magnetization depth is approximately constant if the recording current is the same, and that the magnetization depth increases as the recording current increases from the 0 point, the D point, and the E point. For these reasons, the optimum recording current is set near the point where the frequency characteristics are good and the magnetization depth is uniform. In this way, when performing override erasing on a tape that has already been recorded, it was expected that there would be little unerased material in the deep layer, and that this would lead to a high override erasing rate.

Problems to be Solved by the Invention However, there are problems as described below in, for example, a commercial multi-radial digital magnetic recording and reproducing apparatus that records video, audio, and data with high reliability.

Since commercial digital magnetic recording and reproducing devices used for editing and transmitting broadcast programs generally have a large number of dubbing operations, processing such as interpolation is performed on data that cannot be corrected by decoding using an error correction code, and this process is repeated. and signal deterioration occurs, and as mentioned above, the processing such as interpolation performed on data that cannot be corrected by decoding using error correction codes largely depends on the signal-to-noise ratio of the reproduced signal. One of the factors that reduces the signal-to-noise ratio of the reproduced signal is residual noise during overriding.

In override erasing, an optimal recording current is passed through the head in a frequency range that includes the shortest recording wavelength and the longest recording wavelength so that the magnetization depth is approximately constant on the tape magnetic surface, but the frequency dependence of the magnetization depth is not completely eliminated. , if there is a difference in magnetization depth due to the difference between the frequency of the recorded signal to be erased and the frequency of the newly recorded signal, unerased marks may occur in the deep layer, and repeating between different devices may occur. A similar problem existed in recording due to variations in magnetization depth. The influence of residual noise caused by these unerased marks has led to signal deterioration during dubbing.

Therefore, if an AC erasing head, which has been conventionally used in analog systems, is newly provided, a new problem arises in that not only the head but also a bias oscillation circuit and the like are required, which increases the cost.

In view of the above problems, it is an object of the present invention to provide a digital magnetic recording/reproducing device that eliminates residual noise due to unerased tape even during repeated recording and minimizes signal deterioration.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention is provided with at least two heads whose positions are different when attaching the tape in the longitudinal direction. means for recording a signal via the head; means for selecting a recording signal to the first head from two signals, a first signal and a second signal; means for storing the signal of the second head, means for taking out the reproduction signal of the second head, and means for switching recording and reproduction of the second head,
A first mode records a second signal with the first head and reproduces this recorded signal almost simultaneously with the second head, and a second mode records the first signal with the first head and reproduces the recorded signal with the second head. and a second mode for recording a second signal, and includes means for switching between the first mode and the second mode.

Operation According to the above-described configuration, in the first mode, the first head records the second signal, that is, the target signal, and the second head reproduces this recorded signal almost simultaneously with a slight delay. In the second mode, the first head records the first signal, that is, the erase signal, to improve override erasing, and the second trailing head records the erase signal. A second or target signal can be recorded.

EXAMPLES Hereinafter, examples of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a DAT as a digital magnetic recording/reproducing apparatus according to an embodiment of the present invention. In FIG. 1, 1a, 1b, 2a.

2b are the leading head with positive azimuth, the leading head with negative azimuth, the trailing head with positive azimuth,
A negative azimuth trailing head; 3 is a rotary head to which the leading and trailing heads 1a, 1b, 2a, and 2b are respectively attached; 6 is a recording circuit that supplies recording current to the leading heads 1a and 1b; 9 is a recording circuit; The switch 9 is used to switch the recording signal S1 generated by the first recording signal generating means 11 and the second recording signal 82 from the recording signal input terminal 13. The target recording signal is applied as the selected signal.

On the other hand, signal transmission to the trailing heads 2a and 2b for recording and reproduction is performed via a changeover switch 8, and the recording circuit 6
The recording signal transmission to the reproduction circuit 7 and the reproduction signal transmission to the reproduction circuit 7 are switched. A second recording signal 82 or a multi-purpose recording signal is applied to the recording circuit 6. Further, the output signal of the reproducing circuit 7 is outputted from the terminal 14 as a reproduced signal output. Reference numeral 12 denotes mode switching means for controlling the changeover switch 8 and the changeover switch 9.

FIG. 2 is a diagram showing the relative positional relationship between the head and tape of a DAT according to an embodiment of the present invention. FIG. 2(a) is a view of the rotary cylinder viewed from above, and FIG. 2(b) FIG.

In the DAT configured in this way, the first mode will be explained first.

The first mode is a mode with a simultaneous recording/playback monitoring function. At this time, the target recording signal is input from the terminal 13,
The signal is applied to the recording circuit 5 through the changeover switch 9. The recording current is from the leading head 1a.

1b and is recorded on the tape 4 while forming an inclined track. Subsequently, the reproduction signal of the trailing heads 2L, 2b tracing the recorded track with a slight delay is applied to the reproduction circuit 7 via the changeover switch 8 and taken out as a reproduction signal output through the terminal 14. In this way the first
In this mode, simultaneous recording and playback monitoring during recording is possible.

Next, the second mode will be explained.

The second mode is a mode for especially highly reliable recording when overwriting the already recorded tape 4.

In the second mode, the first recording signal generated by the first recording signal generating means 11 in the preceding heads 1a and 1b is recorded on the tape via the changeover switch 9 and the recording circuit. The first recording signal generating means 11 generates a rectangular wave of about 4.7 MHz, that is, a frequency corresponding to the recording bit rate in DAT using a rotating cylinder of φ30n. This corresponds to the shortest recording wavelength. Recording circuit 6
The magnitude of the recording current can be adjusted by a control signal from the mode switching means 12, and the recording current in the second mode is slightly larger than that in the first mode. As is clear from FIGS. 4 and 6, this is aimed at reliably overriding the magnetization pattern to be erased by slightly increasing the magnetization depth. A tape recorded in this way is
Subsequently, the target recording signal is further overridden via the recording circuit 6 and changeover switch 8 by the trailing headers 2a and 2b tracing the track recorded a little later. The track pattern formed on the tape at this time is as shown in FIG.

Furthermore, since the recording current for the magnetization pattern of 4.gamma.MHz recorded by the preceding head is large, a small portion of the deep layer of the tape remains. However, since the residual magnetization is deep and the residual signal frequency is high, there is a large nubasing loss during reproduction and it is difficult to suffer from residual noise, so the signal-to-noise ratio after override can be maintained sufficiently high. As described above, since already recorded signals can be reliably erased, the reliability of the final data can be sufficiently increased. In particular, residual noise at the longest recording wavelength is eliminated, and the error rate can be improved. In this way, the second
In this mode, highly reliable recording can be made.

In the embodiment, a rectangular wave signal corresponding to the shortest recording wavelength was used as the first recording signal, but it goes without saying that a frequency close to or higher than the shortest recording wavelength may be used, or a sine wave may be used. Nor.

Further, although the recording circuit 5 adjusts the magnitude of the recording current by the control signal from the mode switching means 12, it is not necessary to do this, and even if the same recording current as in the first mode is used, It has an effect.

Effects of the Invention As described above, according to the present invention, the installation of the tape in the longitudinal direction is a means for recording signals through the first head of at least two heads positioned at different positions. , the recording signal to the first head is divided into the first signal and the second head.
means for selecting from two signals, a means for recording the second signal by the second head, a means for taking out the reproduction signal of the second head, and a means for switching recording and reproduction of the second head. a first mode in which a second signal is recorded by the first head and the recorded signal is reproduced substantially simultaneously by the second head; and a first mode in which the first signal is recorded by the first head;
and a second mode in which the second head records a second signal, and is configured to switch between the first mode and the second mode. The second mode allows highly reliable override recording when overwriting an already recorded tape.

The second aspect of the present invention is applied to, for example, a professional multi-radial digital magnetic recording and reproducing apparatus that records audio and data with high reliability.
By using this mode, the residual noise at the time of overriding can be minimized even if dubbing is performed many times, and the signal-to-noise ratio of the reproduced signal can be maintained sufficiently high.

Therefore, according to the present invention, there is almost no probability that decoding cannot correct errors due to error correction codes and processing such as interpolation is required, and signal deterioration does not occur at all. In this way, highly reliable and high-performance dubbing without signal deterioration can be achieved.

Moreover, according to the present invention, there is no need to newly install an AC erasing head, which was required in the conventional analog system, so not only the head but also the bias oscillation circuit etc. are not required, which is also economically advantageous. It is of extremely high industrial value.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a digital magnetic recording and reproducing apparatus according to an embodiment of the present invention, FIGS. 2a and 2b are top and perspective views of a cylinder head used in this embodiment, and FIG. FIG. 4 is a diagram of the track pattern recorded on the tape during override erasing in the embodiment, FIG. 4 is a recording current dependence characteristic diagram of the relative reproduction output, and FIG. 6 is a diagram of the magnetization pattern at each point in FIG. 4. 1a, 1b...preceding head, 2a, 2b...
... Trailing head, 3... Cylinder, 4...
...Tape, 6°6...Recording circuit, 7...
... Regeneration circuit, 8, 9... Changeover switch,
11...First recording signal generating means, 12...
...Mode switching means. Name of agent: Patent attorney Shigetaka Awano and one other person, Ω a) Gusu Diagram Ia, jb --- Kuzu Ding Go,!

Claims (1)

[Claims] A means for recording a signal through a first head that precedes one of the two heads, comprising at least two heads having different attachment positions in the longitudinal direction of the tape; and a recording signal to the first head. means for selecting the second signal from two signals, a first signal and a second signal; means for recording the second signal by the trailing second head; and means for recording the second signal by the second head following the second head; A first mode comprising a means for taking out and a means for switching recording/reproduction of the second head, in which a second signal is recorded by the first head and the recorded signal is reproduced substantially simultaneously by the second head. and a second mode in which the first head records a first signal and the second head records a second signal, and the first mode and the second mode A digital magnetic recording/reproducing device characterized by comprising means for switching.