JPH03250403A - Recording and reproducing device - Google Patents

Abstract

PURPOSE:To provide an exact reproduced signal by changing the bias current to be applied to a reproducing head at the timing at which a recording current is outputted and thereby preventing the reproduced signal from being affected by the crosstalk by the recording current. CONSTITUTION:A pulse train recording amplifier 2 of this device outputs the recording current per time of magnetization inversion to a recording head 1 with the time width (t) satisfying the equation where the gap length of the head 1 is designated as (gl), the max. frequency to be recorded as (f) and the relative speed of a magnetic tape 11 and the head 1 as (v) and records the current in the tape 11. The reproducing head 3 constituted of a magneto-resistant element simultaneously detects a change in the magnetic flux recorded on the tape 11 as a change in electric resistance and sends this change to a reproducing amplifier 12. A bias current control means 4 changes the bias current at the timing at which the recording current flows, thereby lowering the sensitivity of the magneto-resistance element.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a bedroll 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 DAT (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 is 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 is proposed. In FIG. The moving direction, ■ is the relative speed between the recording head and the magnetic tape 11, t is the time width of the recording current, 1 is the recording head, (a) is the current position, (
b) shows the relative position after t seconds due to the movement of the magnetic tape 11. Further, gl is the gap width of the recording head 1.

Here, if the highest frequency of the signal to be recorded is f, then the time width per magnetization reversal of the recording signal is.

1/(2Xf) ...(1
), and the relative speed V between the recording head 1 and the magnetic tape 11 is
Therefore, 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, when a recording current is applied for t seconds, the width of the magnetic tape 11 that is magnetized in the longitudinal direction is determined from the gap width g1 of the recording head 1 by VXt+gl (3
). 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 applied is as follows from equations (2) and (3): vxt+gl ≧ v/ (2X f) .
・If (4), by passing a recording current for seconds,
A single magnetization reversal of the recording signal can be recorded. If equation (4) is solved for t, then 2Xf v In other words, the time width t in which the recording current is applied to perform recording for one magnetization reversal is the time width per magnetization reversal of the recording signal shown in equation (1). Can be made smaller.

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 bias that changes the bias current applied to the magnetoresistive element to a predetermined value at the timing when the recording current is flowing to provide a steady magnetic field to the magnetoresistive element. It is equipped with current control means.

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 bias current control means that applies a bias current to the reproducing head composed of a magnetoresistive element controls the bias current to a predetermined level. value to lower the sensitivity of the playback head and reduce the amplitude of the output signal. Therefore, malfunction of the reproduction amplifier due to crosstalk of the g 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).
Assuming that t satisfies the equation, a pulse train recording amplifier outputs to the recording head 1, 3 a playback head, 4 bias current control means for controlling the bias current value given to the playback head 3, 11 a magnetic tape, and 12 a playback head. 3 is a reproduction amplifier that amplifies the output to a predetermined amplitude; 13 is a recording signal input terminal; 14 is a pulse train clock input terminal; 15 is a reproduction signal output terminal; 16 is a capacitor that couples the reproduction head 3 and reproduction amplifier 12. be.

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. Corresponds to once. Also, the same figure (2
) is the pulse train clock applied to the pulse train clock input terminal 14, (3) in the same figure is the recording current output of the pulse train recording amplifier 2, and (4) in the same figure is the reproduction of the reproducing head 3 when the bias current value is always constant. Signal output: (5) in the same figure shows the reproduction signal output of the reproduction head 3 when the bias current is controlled by the bias current control means.

The operation will be described below with reference to FIGS. 1 and 2. As an example of a bit string of a recording signal given to the pulse train recording amplifier 2, consider repetition of "1" and "0" as shown in FIG. 2 (1). At this time, the pulse train recording amplifier 2 flows a recording current per magnetization reversal, that is, per one bit, based on the gap length gl of the recording head 1, the highest frequency f1 of the recording signal, and the relative speed V between the magnetic tape 11 and the recording head 1. Time span (5)
Let it be an appropriate value t that satisfies the equation. 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).

Connect the pulse train clock input terminal 14 to the pulse train clock input terminal 14 as shown in Fig. 2 (2).
When the pulse train clock shown in FIG. 2 is applied and the recording signal shown in FIG. 2 (1) is applied to the recording signal input terminal 13, the recording current shown in FIG.

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 magnetic flux recorded on the magnetic tape 11 as changes in electrical resistance.

An example of the characteristics of the resistance change R with respect to the magnetic flux change H of the magnetoresistive element is shown in FIG. In order to operate in a region where the resistance change is linear with respect to the magnetic flux change, it is necessary to set the operating point at the center of the region where the characteristic is a straight line, that is, at the point (a) in FIG. Therefore, a current called a bias current is constantly passed through this magnetoresistive element to provide a bias magnetic field Hb due to the bias current. As a result, the magnetic flux change Hsig reproduced from the magnetic tape 11 changes around the bias magnetic field Hb, and can be taken out as a resistance change ΔR.

The resistance change thus obtained is converted into a voltage change by a constant current, and the voltage change is sent to the reproducing amplifier via the capacitor 16.

Here, when the bias current value is always constant, the resistance change with respect to the magnetic flux change is constant, that is, the sensitivity of the magnetoresistive element is constant, and the reproduced signal during recording monitor operation is as shown in Fig. 2 (
As shown in 4), large-amplitude noise due to crosstalk is included at the timing when the recording current is flowing.

Therefore, the bias current control means 4 changes the bias current at the timing when the recording current is flowing to lower the sensitivity of the magnetoresistive element. That is, the operating point is moved to a region where the resistance change with respect to the magnetic flux change is almost O with the characteristics shown in FIG.

For example, with the characteristics shown in Figure 6, the bias magnetic field is set to Hbm.
As axs or Hbmin, the operating point is (b),
Or just move to (C).

As a result, the reproduced signal becomes as shown in FIG. 2 (5), and large-amplitude noise due to crosstalk can be prevented, and malfunction and destruction of the reproduction amplifier 12 can be prevented.

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

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

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

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, FIG. 3 is a block diagram of a pulse train, and FIG. 6 is a diagram of a magnetoresistive element. FIG. 3 is a characteristic diagram showing an example of resistance change with respect to magnetic flux change. DESCRIPTION OF SYMBOLS 1... Recording head, 2... Pulse train recording amplifier, 3... Reproducing head, 4... Bias current control means.

Claims (1)

[Claims] A recording and reproducing apparatus that simultaneously performs recording and reproduction, comprising: a recording head; and a magnetization based on 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 a time width t for flowing a recording current per inversion is t≧1/(2×f)-gl/v; a reproducing head configured with a magnetoresistive element; A recording/reproducing apparatus comprising bias current control means for changing a bias current applied to the magnetoresistive element to a predetermined value at a timing when a recording current is flowing to provide a steady magnetic field.