JPS6120050B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an information detection device, and more particularly, the present invention relates to an information detection device, and more particularly, to an information detection device using a detector having bell-shaped detection characteristics for the positive polarity and negative polarity of an alternating current signal to be reproduced. Detection device.

Hereinafter, a conventional device and an embodiment of the present invention will be described separately for this type of detection device to which a magnetoresistive element is applied.

Figure 1 is a perspective view showing the configuration of the main parts of a detection device using a magnetoresistive element (hereinafter abbreviated as MR element), and 2 is a substrate that holds an MR element 3 and a conductor 4 for generating a bias magnetic field. , the MR element 3 and the bias conductor 4 are usually electrically insulated. 5
1 is a terminal for signal readout, 6 is a current-carrying terminal for the conductor 4, and 2 to 6 constitute the MR head 1. 7 is a magnetic recording medium (hereinafter abbreviated as magnetic tape), and 8 is a magnetization locus recorded on the magnetic tape 7.

Next, conventional signal reproducing means will be explained.

The specific resistance P of the MR element 3 is expressed as ρ=ρ ₀ +△ρ (1), while △ρ is △ρ=△ρ ₀ (1-(Hs) ² /(Hk+HD) ₂ )
It is expressed as (2).

Here, ρ ₀ and △ρ ₀ are constant values determined by the element material, shape, etc., Hs is the signal magnetic field applied to the MR element,
Hk is the anisotropic magnetic field of the MR element, and HD is the demagnetizing field within the MR element.

When a magnetic field H is applied to the MR element 3 from the outer frame, △
ρ has a bell-shaped characteristic as shown in FIG. Therefore, the signal magnetic field Hs is MR from the magnetic tape 7.
Even when applied to element 3, the change in resistivity △ρ is the signal magnetic field.
It changes as if both waves of Hs were rectified. For this reason, conventionally, as shown in FIG. 2, a bias magnetic field Hs was applied from the outside so that the signal magnetic field Hs was applied approximately at the center of the slope of the characteristic curve.

The means for applying the bias magnetic field HB includes means for applying a DC magnetic field from the outside of the MR element 3, and as shown in FIG. The means were at stake. By applying the composite magnetic field of the signal magnetic field Hs and the bias magnetic field HB to the MR element 3 in this way, the signal magnetic field
A resistivity change △ρ close to Hs was obtained.

Next, a means for extracting signals from the conventional MR head 1 to the outside will be described.

Changes in the external magnetic field change △ρ, resulting in MR
The resistance between terminals 5 of element 3 changes. So MR
When a direct current is applied as a bias current to the element 3, the resistance change is converted to a voltage change, and a voltage change corresponding to the input signal magnetic field Hs is obtained at the terminal 5. The signal voltage obtained in this way not only has a lot of distortion because the characteristics of the MR element 3 are not linear, but also has the disadvantage that this distortion component contains many even-order distortion components that are particularly disliked in audio signals. Moreover, when the signal magnetic field Hs becomes large, it becomes saturated and has the disadvantage that the so-called dynamic range cannot be increased.

This invention was made in order to eliminate the above-mentioned drawbacks of the conventional technology, and the bias magnetic field is a high frequency magnetic field, and the output voltage of the MR magnetic head is synchronously detected by a signal related to the bias magnetic field. This is a playback device that has a large dynamic range, has little distortion, and does not generate even-order distortion.

An embodiment of the present invention will be described below. Fig. 3 is a block diagram showing the configuration of an embodiment of the invention, and Figs. 4 and 5 are signal waveform diagrams of various parts to explain its operation. 12 is a high frequency bias generation source, 13 is a distributor, and one of the outputs is a high frequency bias current iB to the bias conductor 4.
Electricity is applied to generate a high frequency bias magnetic field HB.
The remaining two outputs VB of the distributor 13
-VB is synchronous detector 16, 17 for synchronous detection.
is applied to Here, these two outputs have a phase difference of 180°. In such a situation,
When a composite magnetic field (shown in FIG. 4c) of a signal magnetic field Hs (shown in FIG. 4a) and a high-frequency bias magnetic field HB (shown in FIG. 4b) is applied to the MR element 3 from the magnetic tape 7, As shown in Figure 5, △ρ is the fourth
It changes as shown in Figure d. On the other hand, since a DC current is applied to the MR element 3 from the DC source 14 in order to read the change in Δρ, a signal voltage appears between the terminals 5. By extracting this signal voltage in a balanced state, the two input terminals of the amplifier 15 receive the signal voltage Vd=+△V/2 shown in FIG.
and the signal voltage Ve shown in FIG. 4e with the opposite polarity.
=-ΔV/2 is applied. Here, V ₀ is the DC voltage at the operating point, and is the output voltage at the peak point of the high-frequency bias Hs when the signal magnetic field Hs is zero, and △
V is a signal voltage taken out from the MR element 8 by Δρ.

These two signal voltages Vd and Ve are connected to the amplifier 15.
The signal is amplified and applied to the synchronous detectors 16 and 17.

On the other hand, since the synchronous detectors 16 and 17 are applied with AC voltages VB and -VB synchronized with the high frequency bias with a 180° phase difference from the distributor 13, the respective output terminals of the synchronous detectors 16 and 17 are The signal voltages Vf and Vg shown in FIG. 4f and g are obtained.

These signal voltages Vf and Vg are respectively applied to the amplifier 18 and combined by the combiner 19, as shown in FIG.
Obtain the signal voltage Vh shown in
By removing the high frequency bias component, output terminal 2
1, as shown in Figure 4i, the input signal magnetic field Hs
It is possible to reproduce a signal voltage Vi having almost the same waveform as (FIG. 4a).

In the embodiments described above, a magnetoresistive element is used as the detection device, but when the detection device extracts mechanical displacement as a change in electrical resistance value, such as a strain gauge, the detection device exhibits bell-shaped output characteristics. In this case, bias input can be applied by vibrating the strain gauge at high frequency.

Further, another embodiment of the present invention will be explained with reference to FIG. The same functions as in Fig. 3 are given the same reference numerals. An amplifier 22 amplifies the output of the MR element 1, and this output is applied to the synchronous detector 16.
On the other hand, 23 is a phase inverter which inverts the phase of the output of the amplifier 22 and applies it to the synchronous detector 17. The signals are synchronously detected by the synchronous detectors 16 and 17, and added.
By smoothing, a reproduced signal Vi is obtained at the terminal 21. Here, the signal is detected in the synchronous period without passing through the phase inverter 23, and subtracted by the synthesizer 19, thereby obtaining a reproduced signal Vi at the terminal 21. Furthermore, the gist of the present invention can be changed by various modifications such as using a sine wave other than a rectangular wave or a pulsed signal with a different duty cycle as the high frequency bias, or changing the synchronous detection to a sample-and-hold type. Without,
Of course it can be done.

In an information detection device using a detector having a bell-shaped detection characteristic, the present invention superimposes a bias signal having a frequency higher than the frequency components of the information signal on an information signal to be detected, and this bias signal The information signal detected by the detector is extracted as two output signals in a balanced state, these two output signals are each subjected to synchronous detection, and then added, and the frequency component of the bias signal is removed from the output signal to be added. This device is configured to obtain a detection signal by using the bell-shaped characteristic of the detector, so it can be used on both sides of the detector, so it has a wide dynamic range, and even-order distortion is canceled out, so the detection signal has less distortion. It has the effect that a magnetoresistance effect element can be used as a detector, and can have a particularly great effect.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the configuration of the main parts of a detection device using a magnetoresistive element, FIG. 2 is a diagram for explaining the operation of a conventional detection device, and FIG. 3 is a diagram showing an embodiment of the present invention. FIG. 4 is a diagram showing signal waveforms of each part, FIG. 5 is a diagram for explaining its operation, and FIG. 6 is a block diagram showing another embodiment of the present invention. In the figure, 1 is a magnetoresistive head, 3 is a magnetoresistive element, 4 is a bias magnetic field generating conductor, 7 is a magnetic recording medium, 12 is a high frequency bias source, 13 is a distributor, 14 is a DC power supply, 15 and 18 are amplifiers, 16 and 17 are synchronous detectors, 19 is a combiner, and 20 is a low-pass filter. Note that the same reference numerals in the figures indicate the same parts.

Claims (1)

[Claims] 1. A detector having bell-shaped electrical signal output characteristics for positive and negative deviations of the information signal to be detected, which is included in the information signal to be detected. Means for superimposing a bias signal set to a frequency greater than the frequency component on the information signal and inputting it to the detector, and inputting the signal extracted from the detector and a signal synchronized with the bias signal to a synchronous detector. means for obtaining two signals synchronously detected by the synchronous detector at the bias signal period and with a phase difference of approximately 180°; means for synthesizing the two synchronous detection output signals to obtain an approximate signal of the information signal; An information detection device comprising means for removing the frequency component of the bias signal from the composite output signal. 2. The information detection device according to claim 1, wherein the detector is a magnetoresistive element, and the bias signal superimposed on the information signal to be detected recorded on the magnetic recording medium is an alternating magnetic field.