JPH03250404A - Recording/playback 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 poetry recording and reproducing apparatus for recording and reproducing digital signals such as audio signals using a pulse train recording method.

2. Description of the Related Art In recent years, devices that perform high-density digital magnetic recording, such as digital audio tape recorders, have been commercialized. In such devices, a recording signal is converted into a current change by a recording amplifier, then converted into a magnetic field change by a recording head, and recorded as magnetization on a magnetic tape.

In order to perform proper recording, a sufficient current change is required, so the power consumption of the recording amplifier becomes enormous. Therefore, a recording method was proposed in which the recording current is made into intermittent pulses on the condition that the magnetization on the magnetic tape is continuous, that is, a pulse train recording method.

An explanatory diagram of pulse train recording is shown in FIG.

In FIG. 4, 11 is the magnetic tape, arrow 40 is the direction in which the magnetic tape 11 moves, ■ is the relative speed between the magnetic tape 11 and the recording head, t is the time width of the recording current, 1 is the recording head, (a ) is the current position, (b) is the magnetic tape 1
The relative position after t seconds due to the movement of 1 is shown. Also, g
l is the gap width of the recording head 1.

Here, if the highest frequency of the recording signal is f, the time width per magnetization reversal of the recording signal is 1/(2Xf)
... (1), and from the relative speed V between the recording head and the magnetic tape 11, the width of magnetization in the longitudinal direction of the magnetic tape 11 for one magnetization reversal of the recording signal is v/ (2Xf) ... (2
).

On the other hand, the width by which the magnetic tape 11 is magnetized in the longitudinal direction when a recording current is passed for t seconds is vXt0gl (3), based on the gap width g1 of the recording head 1. That is, the magnetized width increases by the gap width gl in addition to the time t during which the recording current is actually applied.

Therefore, when recording one magnetization reversal of the recording signal on the magnetic tape 11, the time width t in which the recording current is passed is as follows from equations (2) and (3): vxt+gl≧v/ (2X f ) ・”(
4), one magnetization reversal of the recording signal can be recorded by passing a recording current for seconds. If equation (4) is solved for t, the time width t in which the recording current is applied to record one magnetization reversal is smaller than the time width per magnetization reversal of the recording signal shown in equation (1). can.

In other words, by maintaining the continuity of magnetization reversal recorded on the magnetic tape 11 and reducing the time width during which the recording current flows per magnetization reversal to 1/(2Xf) or less,
The recording current becomes a pulse for each magnetization reversal, and power consumption can be reduced.

On the other hand, in high-density digital magnetic recording, in order to increase the reliability of recording and reproduction, a recording head is used to record on the medium, and at the same time, a reproduction head is used to reproduce the recorded signal from the medium, and it is necessary to check whether the recorded signal is recorded correctly or not. (hereinafter referred to as a recording monitor) is becoming necessary.

Problems to be Solved by the Invention However, when recording is simply monitored, the level of the reproduced signal is very small compared to the level of the recorded signal, so the recorded signal interferes with the reproduced signal (hereinafter referred to as crosstalk).
Since a signal exceeding the dynamic range is input to the reproducing amplifier, there is a problem that the reproducing amplifier malfunctions, resulting in an inability to obtain an accurate reproduced signal or damage to the reproducing amplifier.

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide a recording/reproducing apparatus that always obtains stable and accurate reproduction signals without being affected by crosstalk even during recording/monitoring operations.

Means for Solving the Problems In order to achieve the above object, the recording and reproducing apparatus of the present invention includes:
From the gap length gl between the recording head and the recording head, the maximum recording frequency f1, and the relative speed V between the magnetic tape and the recording head, the time width for flowing the recording current per magnetization reversal can be calculated as t and the time width that satisfies equation (5). A pulse train recording amplifier, a reproducing head composed of a magnetoresistive element, and a sense current applied to the magnetoresistive element to convert the resistance change of the magnetoresistive element into a voltage change are set to a predetermined value at the timing when the recording current is flowing. Sense current control means for changing the current.

Operation The recording and reproducing apparatus of the present invention has the above-described configuration, so that at the timing when the recording current is output from the pulse train recording amplifier, the sense current control means that supplies the sense current to the reproducing head composed of a magnetoresistive element reduces the sense current. A change in the resistance of the read head results in a small change in voltage, and the amplitude of the output signal from the read head becomes small. Therefore, malfunction of the reproduction amplifier due to crosstalk of the recording current is prevented.

Embodiment FIG. 1 is a block diagram showing a recording/reproducing apparatus according to an embodiment of the present invention, and is an example of application to digital magnetic recording. In Figure 1, 1 is the recording head, and 2 is the time width of the recording current per magnetization reversal of the recording signal (5).
t satisfies the equation, a pulse train recording amplifier outputs to the recording head 1, 3 a reproducing head, 4 a sense current control means for controlling a sense current value given to the reproducing head 3, 1
1 is a magnetic tape; 12 is a reproduction amplifier that amplifies the output of the reproduction head 3 to a predetermined amplitude; 13 is a recording signal input terminal;
4 is a pulse train input terminal, 15 is a reproduction signal output terminal, and 16 is a capacitor for coupling the reproduction head 3 and reproduction amplifier 12.

Furthermore, Fig. 2 is a timing chart when a recording monitor operation is performed with the configuration shown in Fig. 1, and (1) in the figure is a bit string of a recording signal applied to the recording signal input terminal 13, where one bit corresponds to exactly the magnetization reversal. Respond at once. The figure (2) shows the pulse train clock applied to the pulse train clock input terminal 14, the figure (3) shows the recording current output of the pulse train recording amplifier 2, and the figure (4) shows reproduction when the sense current value is always constant. Playback signal output of head 3, same figure (5)
is the reproduction signal output of the reproduction head 3 when the sense current is controlled by the sense current control means.

The operation will be described below with reference to FIGS. 1 and 2. As an example of the bit string of the recording signal supplied to the pulse train recording amplifier 2, consider the repetition of "1" and '0' as shown in FIG. Gap length gli of 1 Maximum frequency f1 of the recording signal Based on the relative velocity V between the recording head 1 and the magnetic tape 11, the time width for flowing the recording current per magnetization reversal is set to t shown in equation (5).

An example of the configuration of the pulse train recording amplifier 2 is shown in FIG.

Here, 31 is a current amplifier, and 32 is an exclusive OR (EX-
OR). If the pulse train clock shown in FIG. 2 (2) is applied to the pulse train clock input terminal 14 and the recording signal shown in FIG. 2 (1) is applied to the recording signal input terminal 13, the result shown in FIG. The recording current shown is output to the recording head 1.

A recording signal is recorded on the magnetic tape 11 by this recording current. At the same time, the signal is also reproduced as a reproduction signal by the reproduction head 3. The reproducing head 3 is composed of a magnetoresistive element, and detects changes in the magnetic flux recorded on the magnetic tape 11 as changes in resistance. Therefore, a current called a sense current is constantly passed through this magnetoresistive element to convert the resistance change into a voltage change, and the voltage change is sent to the reproducing amplifier via the capacitor 16. This voltage change is directly proportional to the sense current value according to Ohm's law.

Here, if the sense current value is always constant, the reproduced signal will contain large-amplitude noise due to crosstalk at the timing when the recording current is flowing, as shown in FIG. 2 (4). Therefore, the sense current control means 4 makes the sense current smaller than usual at the timing when the recording current is flowing, and makes the resistance change due to crosstalk a smaller voltage change than usual.

Therefore, the reproduction signal becomes as shown in FIG. 2 (5), and if the sense current is made sufficiently small, malfunction and destruction of the reproduction amplifier 12 due to crosstalk can be prevented.

An example of the configuration of the sense current control means 4 is shown in FIG.

In FIG. 5, 14 is a pulse train clock input terminal, 50 is a sense current output terminal, 51 is an inverter, 5
2 is a current source circuit, and 53 is a transistor switch.

With this configuration, when the pulse train clock is "H", that is, at the timing when the recording current is flowing, almost no sense current flows.

Effects of the Invention As described above, according to the present invention, the reproduced signal is not affected by crosstalk caused by the recording current during the recording monitor operation, so that an accurate and highly reliable reproduced signal can always be obtained. It is possible to realize a highly stable recording and reproducing device with a simple circuit configuration, which is extremely useful in practice.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a recording/reproducing apparatus according to an embodiment of the present invention, FIG. 2 is a timing chart of each signal in FIG. 1, and FIG. 3 is a pulse train block diagram. DESCRIPTION OF SYMBOLS 1... Recording head, 2... Pulse train recording amplifier, 3... Playing head, 4... Sense current control means.

Claims (1)

[Claims] A recording/reproducing apparatus that simultaneously performs recording and reproduction, comprising: a recording head; a gap length gl between the recording head; a maximum recording frequency f; and a relative speed v between the magnetic tape and the recording head. A pulse train recording amplifier in which the time width t for flowing a recording current per magnetization reversal is t≧1/(2×f)-gl/v; a reproducing head composed of a magnetoresistive element; and the magnetoresistive element. and a sense current control means for changing a sense current applied to the magnetoresistive element to a predetermined value at a timing when a recording current is flowing in order to convert a change in resistance into a change in voltage. .