JPS60197908A - Digital magnetic reproducing device - Google Patents

Abstract

PURPOSE:To reproduce a signal having no code error making an analog signal obtained by executing an amplitude equalization and a waveform equalization to an isolated wave signal of a magnetic head pass through an asymmetrical isolated wave correcting circuit, and thereafter, discriminating and reproducing a digital signal. CONSTITUTION:An output of a magnetic head 1 using a magneto-resistance element is amplified by an amplifier 2, and thereafter, inputted to an amplitude equalizing circuit 3. A high frequency component amplitude is emphasized by the circuit 3, and said output is converted to a signal of an optimum frequency band by a delay equalizing circuit 4, and thereafter, it is inputted to an asymmetrical isolated wave correcting circuit 5. The circuit 5 consists of rectifying circuits 51, 52 and a synthesizing circuit 53, and as for the circuits 51, 52, the respective rectifying directions are different, and also the gain is different. A composite output 5a of the circuit 53 becomes an up-and-down symmetrical isolated wave, and it is integrated by an integration circuit 6. An integral output 6a and a DC value 7a obtained by a DC detector 7 from the output 6a are compared by a comparing circuit 8, and an output corresponding to logic ''1'' or ''0'' is obtained and sent out to a demodulator. In this way, a digital signal having no code error can be discriminated and reproduced.

Description

TECHNICAL FIELD The present invention relates to an apparatus for reproducing digital signals from a digital magnetic recording medium such as a digital audio tape, and more particularly to a reproducing apparatus using a magnetic head using a magnetoresistive element.

When a magnetic flux responsive magnetoresistive element or a Hall element is used as a reproducing head for a digital magnetic recording medium, sensitivity becomes independent of tape speed. Because the sensitivity of a coil-type magnetic head is proportional to tape speed, at low or normal tape speeds, the sensitivity of a flux-responsive head is much greater than that of a coil-type head. Among these, magnetoresistive elements (hereinafter referred to as MR elements) output an output proportional to the square of the magnetic field, and if constructed from a ferromagnetic metal thin film, the element area can be small, so it is suitable for integration into a multi-head. There is.

The resistance change characteristics of the MR Shiko with respect to the magnetic field are as shown in FIG. In the figure, the vertical axis indicates the resistance value R of the MR transducer, and the horizontal axis indicates the magnetic field H applied perpendicularly to the MR transducer surface.

As shown in the figure, the resistance changes non-linearly near zero magnetic field H, so when the bias DC magnetic field H is constant as shown in the figure,
e is added to the center of the region where the resistance change is linear, and the measurement magnetic field is changed in the vicinity of this magnetic field Ho to perform the linear measurement.

An MR element is fixed close to the top of a magnetic recording medium such as a horizontally magnetized tape, and the signal reproduced by the magnetic head and subsequent amplitude equalization when the recording medium is run.
FIG. 2 shows the signal waveform after waveform equalization. The magnetization pattern in FIG. 2 shows the state of horizontal magnetization on the tape, and the direction of the vertical magnetic field H changes as shown at the magnetization reversal point. When the tape is run, the MR element receives a bias DC magnetic field Ho.
Since the output of the magnetic head changes in the vicinity of , the output of the magnetic head is output as an alternating current signal train of solitary waves as shown in the figure. The amplitude frequency characteristics of this solitary wave signal are improved by an amplitude equalization circuit. In the figure, the effect of amplitude equalization is shown for the waveform indicated by EQ. Next, a delay equalization circuit performs waveform equalization to obtain a frequency characteristic with an optimal passband (Nyquist bandwidth). The waveform of the signal after waveform equalization is separated so that each solitary wave has less mutual interference.

The solitary wave signal sequence obtained by amplitude equalization and waveform equalization is differentiated or integrated, and an identification circuit identifies 11" or 101 to generate a digital signal.Identification is performed using a so-called eye diagram. The discrimination level is set at the center of the eye aperture amplitude.

However, in the above-mentioned amplitude equalization and waveform equalization, since the vertical asymmetry of the amplitude of the original waveform is not corrected, the asymmetry of the original waveform appears as it is in the input waveform of the identification circuit. For this reason, there are disadvantages in that the amplitude asymmetry of the original waveform makes it difficult to identify the eye aperture ratio9, and that a sign error occurs in the digital signal.

Since a magnetic head using an MR element has essentially non-linear resistance-magnetic field characteristics, a bias magnetic field is applied as described above to linearize the original waveform so that the amplitude is symmetrical. However, in high-density recording media with as many as 10 to 20 tracks, the number of magnetic heads is large, and it is difficult to adjust the bias point of each magnetic head appropriately. Variations in symmetry will occur. Therefore, some means must be taken to correct the asymmetry.

DISCLOSURE OF THE INVENTION It is an object of the present invention to develop a digital magnetic field that corrects the vertical asymmetry of the solitary wave signal after amplifying and waveform equalizing the solitary wave signal of a magnetic head and before inputting it to an identification circuit. The purpose is to provide a playback device.

That is, the digital magnetic reproducing device according to the present invention uses a series of circuits with different rectifying directions and different gains as a pre-processing circuit before the operation of identifying and reproducing digital signals.
The present invention is characterized by comprising an asymmetric solitary wave correction circuit consisting of two rectifier circuits to which reproduced solitary wave signals are manually input in parallel, and a synthesis circuit that synthesizes the respective outputs of the rectification circuits.

FIG. 3 shows an overall circuit block diagram of the digital magnetic reproducing apparatus of the present invention. The output of a magnetic head 1 using an MR element is amplified by a head amplifier 2 and then input to an amplitude equalization circuit 3. The amplitude equalization circuit 3 emphasizes the high frequency component amplitude, and the delay equalization circuit 4 makes the signal in the optimum frequency band, and then the output 4
a is input to the asymmetric solitary wave correction circuit 5. This asymmetric solitary wave correction circuit 5 consists of two rectifier circuits 51 and 52 and a combining circuit &, and each rectifier circuit 51, 52Fi has a different direction of rectification and a different gain. For example, if the positive direction amplitude of the input asymmetric solitary wave is smaller than the negative direction amplitude, the gain of the rectifier circuit (referred to as rectifier circuit 51) having positive direction rectification characteristics will be higher than that of the rectification circuit 52 having negative direction rectification characteristics. Adjust it so that it is large. Therefore, the output 5a obtained by combining the outputs of both rectifying circuits 51 and 52 with the combining circuit &
becomes a vertically symmetrical solitary wave.

The output 5a is integrated by an integrating circuit 6, and a DC value 7 is obtained from this output 6a and a DC detector 7 from this output 6a.
Compare a with comparison port wr8 and get logic @1″ or logic″0
A corresponding output is obtained and sent to a demodulator (not shown).The DC detector 7 is for compensating for fluctuations in the DC component.

As explained above, in the gain magnetic reproducing apparatus according to the present invention, an asymmetric solitary wave signal from a magnetic head 1 using an MR element or the like is corrected into a vertically symmetrical solitary wave by the asymmetric solitary wave correction circuit 5. Ru. In the signal 6a obtained by integrating this signal 5a by the integrating circuit 6, the eye opening ratio of the eye diagram is widened, there is no code amount interference, and code errors can be prevented. Particularly in systems with high code transmission speeds, when reproducing data using multiple heads using MR elements, a common constant bias DC magnetic field is applied to the heads, and then asymmetric solitary wave correction is applied to each head. By adjusting circuit 5, for all heads,
Digital signals without code errors can be reproduced.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a specific circuit of the asymmetric solitary wave correction circuit 5, which is the essential part of the present invention, will be explained with reference to FIGS. 4 and 5. In FIG. 4, the output 4a of the delay equalization circuit 4 of FIG. 3 is amplified by an amplifier 11 and input to diodes 12 and 13. The diodes 12 and 13 have different rectifying directions, and their respective output terminals are connected through a resistor 14, and the midpoint of the resistor 14 is connected to the output terminal p of the asymmetric solitary wave correction circuit 5. Further, the output terminal p is grounded to a common ground via a resistor R3. Now, if each resistance value divided by the midpoint of the resistor 14 is < R1, R2 as shown in the figure, the positive amplitude (10 A) of the signal 4a will appear at the output terminal as 3 (10 A) x □. , R1+ Rs Similarly, negative oscillation (-B) is expressed as (-B) Therefore, by changing the ratio of RIIR 4, it is possible to change the gain ratio of each rectifier circuit and obtain output 5a of the same amplitude for asymmetrical positive and negative amplitudes.

FIG. 5 shows the improvement result, and shows the asymmetric input signal 4a and the waveform of the output 5a of the asymmetric solitary wave correction circuit 5. The inhibiting force 5a has a vertically symmetrical waveform. Fourth
In the figure, one CI*02 capacitor is connected between the output terminal -p and each diode 12 and 13, but this is for correcting the upper and lower phases of the solitary wave, and is unnecessary if there is no phase shift. be.

Next, the embodiment shown in FIG. 6 will be explained. Amplifier 11 in FIG.
Diodes 12 and 13 are incorporated into an operational amplifier to form half-wave rectifier circuits 16 and 17, and the gain of each rectifier circuit is adjusted by a feedback resistor=F□+RF2. Therefore, the midpoint of the resistor 14 is fixed. The operating characteristics are exactly the same as the circuit of FIG.

In addition, in the overall circuit block diagram of FIG. 3, as shown in the figure, the identification circuit is configured to generate a signal 5a corrected to a vertically symmetrical solitary wave.
It goes without saying that the present invention can be applied to a differential method in which the reproduced waveform is input to a differentiating circuit and the reproduced waveform is calculated at the zero-crossing point.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the characteristics of the MR element, Fig. 2 is a diagram showing the magnetization pattern of the recording medium and the waveform of the reproduction solitary wave, Fig. 83 is a block diagram of the magnetic reproduction system showing the principle of the present invention, and Fig. 4 ,
FIG. 6 shows an embodiment, and FIG. 5 shows an improvement in amplitude asymmetry according to the present invention. 1. Magnetic head, 2. Amplifier, 3.
... Amplitude equalization circuit, 4... Delay equalization circuit, 5... Asymmetric solitary wave correction circuit, 51, 52... Rectification circuit, O... Synthesis circuit, 6.
...Integrator circuit, 7...DC detector, 8...Comparison circuit, 11...Amplifier, 12, 13...Diode, 14...Resistor, 16, 17...Half-wave rectifier circuit , Rs e R2...Resistor, Oxleex...Capacitor, RF engineer 1RF2...Feedback resistor. Patent Applicant NEC Home Electronics Co., Ltd. Agent Patent Attorney Akihi Sato Old Third Il! ! 1 Figure 4 jf! 5 Figure → Figure 6

Claims (1)

[Claims] In a digital magnetic reproducing device, a preprocessing circuit with different rectification directions is used as a preprocessing circuit before the operation of identifying and reproducing a digital signal from an analog signal obtained by performing waveform equalization during amplitude equalization on a solitary wave signal of a magnetic head. The present invention is characterized by comprising an asymmetric solitary wave correction circuit comprising two rectifier circuits whose gains are different from each other, to which the analog signals are input in parallel, and a synthesis circuit which synthesizes the respective outputs of the rectification circuits. Digital magnetic reproducing device.