JPS6035302A - Reproduction circuit of magnetic recording signal - Google Patents

Abstract

PURPOSE:To obtain a reproduced output signal which has good linearity and good S/N without having distortion by providing a current source for biasing which supplies the alternating current to saturate or saturate nearly the resistance of a magneto-resistance effect element to a winding, a flip-flop which is driven by the output from a magnetic head and a low-pass filter. CONSTITUTION:The resistance of a magneto-resistance effect MR element 1-1 shows high resistance at the point of the time when the intensity of the input magnetic field impressed thereto goes to ''0''. As a result the output voltage (c) of the MR head 1 forms a pulse waveform at the point of the time when the intensity of the biasing alternating magnetic field having a triangular waveform goes to ''0'' till time t1, at the point of the time when the intensity of the combined magnetic field consisting of the biasing alternating magnetic field having a triangular waveform and the input magnetic field goes to ''0'' till time t2 in succession to the above and at the point of the time when the intensity of the combined magnetic field consisting of the bias alternating magnetic field having a trigangular waveform and the input magnetic field goes to ''0'' till time t3 in succession thereto. The output from a T flip-flop 7 is supplied to a low-pass filter 8 by which the frequency component of the intensity of the biasing alternating magnetic field is removed and only the signal component is obtd. as shown by (e). The output corresponds to the input magnetic field.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording signal reproducing circuit that detects and reproduces signals recorded on a magnetic recording medium through a reproducing head using a magnetoresistive element.

(Prior art) Magnetoresistive elements (hereinafter referred to as MR elements) utilize the property that the electrical resistance of a ferromagnetic material is extremely high when the direction of magnetization is parallel to the direction of current, and low when the direction of magnetization is perpendicular to the current direction. , which detects magnetic fields and converts them into electrical signals. - As an example, the characteristics of an MR element with an axis of easy magnetization in the direction of current are shown in Figure 1. In Figure 1, the horizontal axis represents the strength of the applied magnetic field, and the vertical axis represents the resistance value. ing. The change in resistance value is usually several percent, but as shown in FIG. 1, the change in resistance value with respect to changes in the magnetic field is linear and does not occur. When trying to obtain a signal proportional to the strength of the input magnetic field from the MR element, by adding a bias magnetic field shown in B in Figure 1 in advance, approximately The resistance value change is regarded as a straight line.

FIG. 2 is a block diagram of a conventional magnetic recording signal reproducing circuit using a magnetic head using an MR element (hereinafter referred to as MR head). In FIG. In addition to the MR element 1-1, the head 1 includes a winding 1-2 for applying a bias magnetic field.2 is a constant current source that supplies a direct current to convert the resistance change of the MR element 1 into a voltage signal. , 3 is a current source for applying a bias magnetic field, and 4 is an AC amplifier for amplifying the reproduced output signal.

When using the conventional magnetic recording signal reproducing circuit shown in FIG. 2, the reproduced output signal is approximately proportional to the strength of the input magnetic field generated from the magnetic recording medium 5 such as a magnetic tape on which the signal to be reproduced is recorded. However, the linearity cannot be said to be good.

In order to obtain good linearity, the strength of the input magnetic field must be kept within a very small range, and therefore the reproduced output signal also becomes weak, resulting in a loss of S.

(Object of the Invention) The present invention has been made in view of the above, and is a magnetic recording signal reproducing circuit that can eliminate the above-mentioned drawbacks and obtain a reproduced output signal with good linearity, no distortion, and a good S. The purpose is to provide

The present invention will be explained below with reference to Examples.

(Structure and operation of the invention) FIG. 3 is a block diagram showing a first embodiment of the present invention.

In the first embodiment of the present invention, the same components as those of the conventional magnetic recording signal reproducing circuit shown in FIG. 2 are denoted by the same reference numerals, and the explanation thereof will be omitted.

6 replaces the current source 3 and supplies output to the winding 1-2.
-2 to provide a bias magnetic field, the current source 6 outputs a triangular wave, sawtooth wave, trapezoidal wave, or sine wave current, and the current value is the same as that of the MR element 1-1. The value is set to such a value that a magnetic bias of a strength as shown by C in FIG. 1, for example, is applied until the resistance reaches saturation or near saturation.

The output of the AC amplifier 4 is supplied to the T-flip float 7,
Q output coverrow of T frizzo flop 7, f filter 8
It is configured to output via.

In the first embodiment of the present invention configured as described above, the MR
The element 1-1 is magnetically biased by an alternating magnetic field generated by a triangular, sawtooth, trapezoidal or sinusoidal bias current outputted from the current source 6.

Further, due to the bias magnetic field caused by the current from the current source 6, the resistance of the MR element 1- reaches or approaches saturation.

Furthermore, the frequency of the current output from the current source 6 is sufficiently higher than the highest frequency of the signal to be reproduced, and is set to at least twice the highest frequency.

The operation will be described below using an example in which the current waveform output from the current source 6 is a triangular wave.

1/' The input magnetic field applied to the MR head 1 by the magnetic recording medium 5 has a magnetic field strength of 0'' until time t1, and then a positive magnetic field strength until time t2, as shown in FIG. It is assumed that the strength of the magnetic field is "a predetermined negative value" until time t3.

The waveform of the current supplied from the current source 6 is as shown in FIG. 4(b). Therefore, the strength of the bias alternating magnetic field applied to the MRR element 1-1 changes in the shape of a triangular wave as shown in FIG. 4(b).

Therefore, the resistance of the MRR element 1-1 exhibits a high resistance when the strength of the input magnetic field applied to the MR element 11 becomes "O". As a result, the output voltage of the MR head 1 is as shown in Fig. 4 (C
), at time 111, the strength of the triangular wave-shaped bias alternating magnetic field becomes "0", and until time t2, the triangular wave-shaped noisy alternating magnetic field and the input magnetic field (positive predetermined value) are synthesized. At the time when the strength of the magnetic field becomes "0" and subsequently until time t3, the strength of the composite magnetic field of the triangular wave-shaped bias alternating magnetic field and the input magnetic field (predetermined negative value) is 0.
It becomes a Noyals waveform at the point when . In addition, Fig. 4(c)
In the figure, the voltage due to the steady division of the resistance of the MRR element 1-1 is omitted, and only the variation is shown.

As is clear from FIG. 4(c), when there is no input magnetic field, the pulses output from the MR head 1 are generated at regular intervals, but when an input magnetic field is applied, the pulse intervals become narrower and narrower alternately, The interval is proportional to the strength of the input magnetic field, and the order of density is reversed depending on the polarity of the strength of the input magnetic field.

The T flip-flop 7 is connected to the MR head 1 in FIG.
) In response to the pulse output shown in Figure 4(d), the Q output generates an output with a duty ratio of 50% when there is no input magnetic field, and when the input magnetic field is applied, the Q output generates a Generates an output pulse with a duty ratio that corresponds to the strength of the magnetic field.

The output of the T flip-flop 7 is supplied to a low-pass filter 8, which removes the frequency component of the strength of the Yotte bias alternating magnetic field, and only the signal component is obtained as shown in FIG. 4(,). This output corresponds to the input magnetic field.

In the above explanation, the current waveform from the current source 6 is a triangular wave, but the same applies to sawtooth, trapezoidal, or sine waves, and in the case of a sine wave, its amplitude is input. The linearity of the reproduced output is improved because the pulses are converted into pulses with intervals corresponding to the strength and polarity of the magnetic field and are processed by the flip-flop 7 and the low-pass filter 8. depends only on the linearity near the zero-crossing point of the current waveform of the current source 6 that provides the bias magnetic field, and does not depend on the resistance change characteristics of the MRR element 1-1. Therefore, t for the strength of the input magnetic field of the reproduced output signal
O1 linearity can be made good, and Sc can also be improved.

Next, a second embodiment of the present invention will be described.

FIG. 5 is a block diagram showing the configuration of a second embodiment of the present invention.

The second embodiment of the present invention is based on T in the first embodiment of the present invention.
In place of the flip-flop 7, a multiplier 9 multiplies the output of the amplifier 4 by a voltage obtained by converting the output current of the current source 6.
Connect and configure.

In the second embodiment of the present invention constructed as described above, the operation will be explained assuming that the same manual magnetic field as in the first embodiment of the present invention is used and the output waveform of the current source 6 is a triangular wave.

The strength of the input magnetic field is shown in Figure 6 (a), the output waveform of the current source 6 is shown in Figure 6 (b), and the output voltage waveform of the MR head 1 is shown in Figure 6 (
As shown in c), it is the same as FIGS. 4(a) to (c).

The output voltage waveform of the multiplier 9, which is obtained by multiplying the output voltage of the MR head 1 by the voltage obtained by converting the output current of the current source 6, is the sixth waveform.
The result is as shown in Figure (d). That is, the multiplier 9 does not generate an output when there is no input magnetic field, but outputs a pulse voltage whose polarity and pulse interval vary depending on the strength and polarity of the input magnetic field.

This output of multiplier 9 is fed to low pass filter 8,
The output voltage waveform of the low-pass filter 8 is shown in Fig. 6(e) K
It will be as shown.

The output voltage waveform of the low-pass filter 8 has a shape that is an inversion of that shown in FIG. 6(a), but the polarity can be easily reversed by appropriate means, so that the reproduced output signal has the same shape as that shown in FIG. 4(e). be able to.

Further, an alternating voltage having the same period as the period of the output current of the current source 6 is supplied to the multiplier 9 instead of the voltage obtained by converting the output current of the current source 6 to the output of the MR head 1 and the multiplier 9. The same applies to multiplication. In this case, the waveform of the alternating voltage needs to have a change in amplitude proportional to a change in time before and after the O-crossing point.

Alternatively, the output current of the current source 6 may be multiplied by a current obtained by converting the output voltage of the MR head 1 into a current.

In the second embodiment of the present invention, for the same reason as in the first embodiment, a reproduced output signal with excellent linearity and good S/H can be obtained.

Next, a third embodiment of the present invention will be described.

FIG. 7 is a block diagram showing the configuration of a third embodiment of the present invention.

In the first and second embodiments of the present invention, the MR element 1-
In order to convert the resistance value of 1 into a voltage, a constant current source 2 that supplies a direct current is used, but in the third embodiment of the present invention, the output current of a current source 6 is used.

In the third embodiment of the present invention, the constant current source 2 and the multiplier 9 in the second embodiment of the present invention are omitted, and the output current of the current source 6 is branched by a distributor 10 and supplied to the winding 1-2. The voltage is also supplied to the MR element 1-1, and the resistance value of the MR element 1-1 is converted into a voltage via the distributor 10. The output voltage from the MR head 1 is supplied to an amplifier 4 for amplification, and the output of the amplifier 4 is a steady-state component removal circuit that removes the voltage component due to the product of the steady-state resistance value of the MR element 1-1 and the current of the current source 6. 11 and output via a low-pass filter 8.

In the third embodiment of the present invention, the voltage output from the MR head 1 is the product of the resistance value of the MR head 1 and the output current of the current source 6. Furthermore, excluding the steady resistance, the resistance of the MR element 1-1 changes as shown in FIG. 6(c) due to the input magnetic field. However, since the output current waveform of the current source 6 is as shown in FIG. 6(b), 1. The output voltage waveform of the MR head 1 outputted via the steady-state component removal circuit 11 has the same shape as that shown in FIG. 6(d). Therefore, the reproduced output signal waveform after passing through the low-pass filter 8 is as shown in FIG. 6(e).

Further, the same effect can be obtained even if an alternating current having the same cycle as the output current of the current source 6 is supplied to the MR element 1-1 instead of the output current of the current source 6.

It is as good as in the case of . Further, the constant current source 2 can be omitted.

(Effects of the Invention) As explained above, according to the present invention, the linearity of the reproduced output signal with respect to the strength of the input magnetic field depends on the linearity near the zero-crossing point of the output current waveform of the current source for applying the bias magnetic field. Since it does not depend on the resistance change characteristics of the MR element, it is possible to obtain a reproduced output signal with excellent linearity that is proportional to the strength of the input magnetic field even if the strength of the input magnetic field changes greatly.

Furthermore, the quality of the reproduced output signal is good and there is no distortion.

Furthermore, in order to further improve the linearity, it is easy and effective to feed a part of the reproduced output signal back to the winding for applying the bias magnetic field.

[Brief explanation of the drawing]

FIG. 1 is a characteristic diagram showing the resistance change characteristics of the MR element. FIG. 2 is a block diagram of a conventional magnetic recording signal reproducing circuit. FIG. 3 is a block diagram showing the configuration of the first embodiment of the present invention. FIG. 4 is a waveform diagram for explaining the operation of the first embodiment of the present invention. FIG. 5 is a block diagram showing the configuration of a second embodiment of the present invention. FIG. 6 is a waveform diagram for explaining the operation of the second embodiment of the present invention. FIG. 7 is a block diagram showing the configuration of a third embodiment of the present invention. 1...MR head, 1-1...MR element, knee 2.
...Winding, 2... Constant current source, 6... Current source, 7...
・T flip filter, 8...Low pass filter, 9
... multiplier 11-device, 10... divider. Patent Applicant Trio Co., Ltd. Agent Patent Attorney Nobu Sunako Mistakes 1 Figure 2 Figure 3 Figure 4 (C) JlJ Sat■■''L Publication'' 10th Edition Figure 5

Claims (7)

[Claims] (1) In a magnetic recording signal reproducing circuit for reproducing signals recorded on a magnetic recording medium by a magnetic head comprising a magnetoresistive element and a winding for generating a bias magnetic field, the resistance of the magnetoresistive element is A bias ammeter that supplies an alternating current to the winding at or near saturation, a flip-flop driven by the output of the magnetic head, and a low-pass filter to which the output of the flip-flop is supplied. A magnetic recording signal reproducing circuit comprising: (2) The output current waveform of the current source is a triangular waveform, a sawtooth waveform,
2. The magnetic recording signal reproducing circuit according to claim 1, wherein the magnetic recording signal reproducing circuit has either a trapezoidal waveform or a sine waveform. (3) In a magnetic recording signal reproducing circuit that reproduces signals recorded on a magnetic recording medium by a magnetic head comprising a magnetoresistive element and a winding for generating a bias magnetic field, the resistance of the magnetoresistive element saturates. or a bias current source that supplies an alternating current up to near saturation to the winding, and a multiplier that multiplies the output of the magnetic head by a signal with a period matching the period of the output current of the current source; A magnetic recording signal reproducing circuit comprising: a low-pass filter to which the output of the multiplier is supplied. (4) The output current waveform of the current source is a triangular waveform, a sawtooth waveform,
4. The magnetic recording signal reproducing circuit according to claim 3, wherein the magnetic recording signal reproducing circuit has either a trapezoidal waveform or a sine waveform. (5) The signal having the same period as the output current of the current source is a voltage obtained by converting the output current of the current source.
A magnetic recording signal reproducing circuit according to claim 3. (6) In a magnetic recording signal reproducing circuit that reproduces a signal recorded on a magnetic recording medium by a magnetic head comprising a magnetoresistive element and a winding for generating a bias magnetic field, the resistance of the magnetoresistive element is saturated or A bias current source that supplies an alternating current up to near saturation to the winding; and a low-nos filter that waves the output voltage of the magnetic head; A magnetic recording signal reproducing circuit characterized in that a current having a cycle equal to the cycle of an output current of a source is supplied to the magnetoresistive element. (7) The output current waveform of the current source is a triangular waveform, a sawtooth waveform,
7. The magnetic recording signal reproducing circuit according to claim 6, wherein the magnetic recording signal reproducing circuit has either a trapezoidal waveform or a sine waveform.