JPH0474763B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic recording/reproducing circuit applied to a magnetic recording/reproducing apparatus using a perpendicular recording medium and a magnetoresistive reproducing head.

[Prior art and its problems]

In general, perpendicular recording media such as CoCr are known to have higher density recording characteristics than internal recording media, and magnetoresistive playback heads are known to have high playback sensitivity. Until now, research has focused mainly on internal recording media, but there have also been reports on the reproduction characteristics of a combination of a perpendicular recording medium and a magnetoresistive reproduction head ("Summary of the 6th Annual Meeting of the Japan Society of Applied Magnetics," ”
17aB-10).

According to the combination of this perpendicular recording medium and a magnetoresistive reproducing head, the reproducing waveform at low recording density becomes a rectangular waveform, and the waveform may be significantly asymmetrical. This is significantly different from the unimodal reproduced waveform as seen in the media and ring head combination. However, there has been no known reproducing circuit that can demodulate data with a small bit shift in the case of such an asymmetrical rectangular wave.

[Purpose of the invention]

An object of the present invention is to demodulate data with a small bit shift to a high recording density when the reproduction waveform at low density becomes an asymmetric rectangular waveform, as in the case of a combination of a perpendicular recording medium and a magnetoresistive reproduction head. The object of the present invention is to provide a magnetic recording/reproducing circuit that can perform the following functions.

[Structure of the invention]

The configuration of the magnetic recording and reproducing circuit of the present invention includes a differentiating circuit that differentiates a reproducing input signal from a reproducing magnetic head, a delay circuit that delays the output voltage of this differentiating circuit, and an attenuator that attenuates the output voltage of this delay circuit. and a zero-cross detection circuit that detects a point in time when the difference between the output voltage of the differentiation circuit and the output voltage of the attenuator becomes zero.

〔Example〕

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a circuit diagram of one embodiment of the magnetic recording/reproducing circuit of the present invention, and FIGS. 2(a) to 2(d) are waveform diagrams showing the operation of the magnetic recording/reproducing circuit of FIG. 1. The magnetic recording/reproducing circuit of this embodiment is composed of a differentiating circuit 1, a delay circuit 2, an attenuator 3, and a zero-cross detection circuit 4.

The reproduction waveform produced by the combination of the perpendicular recording medium and the magnetoresistive reproduction head is an asymmetrical rectangular waveform as shown in FIG. 2a. When this reproduced waveform is input to the differentiator circuit 1, its output is differentiated,
The waveform becomes as shown in FIG. 2b. When the output voltage of the differentiating circuit 1 is passed through a delay circuit 2 and an attenuator 3, an attenuated delayed waveform as shown in FIG. 2c is obtained. By optimally adjusting the delay time of the delay circuit 2 and the attenuation ratio of the attenuator 3, the difference between the output waveform of the attenuator 3 and the output waveform of the differentiator 1 can be made almost symmetrical as shown in Fig. 2d. It can be a dipulse. Therefore, the output of the differentiating circuit 1 and the attenuator 3
By inputting the output of the bit and the output of the bit into the zero cross detection circuit 4 and detecting the point in time when the difference between these output voltages becomes zero, the interference between bits becomes almost symmetrical before and after the bit, so the bit shift can be reduced. , it becomes possible to reproduce higher-density signals.

〔Concrete example〕

As a specific example, data was recorded on a CoCr/NiFe two-layer perpendicular recording medium using a single magnetic pole type head and reproduced using a shielded magnetoresistive type reproducing head. The gap length between the shields was 0.4μm, and the media
The relative speed between the heads was 1 m/s. Using these media and heads, the output of the magnetoresistive reproducing head was amplified and then demodulated by a reproducing circuit.

The reproduction circuit of this embodiment includes a differentiator circuit 1 which is a current feedback circuit, a delay circuit 2 which uses a glass delay line, an attenuator 3 which uses a variable resistor, and a zero cross circuit which uses a differential comparator. The differential time constant of the differentiating circuit 1 was 50 ns, the delay time of the delay circuit 2 was 50 ns, and the attenuation rate of the attenuator 3 was 50%.

The results of measuring the bit shift of "11" when a repeating pattern of "110" is recorded and reproduced on a recording medium using the MFM method are shown as curve A in FIG. At this time, the recording density when the bit shift was 20% was 40 KBPI. Also, curve B in Figure 4
1 is a comparative example, and shows the bit shift when the zero cross is directly detected after amplifying the reproduction output from the magnetoresistive reproduction head. At this time, the recording density when the bit shift was 20% was 30KBPI.
Therefore, it has become clear that the magnetic recording/reproducing circuit of this example is more suitable for high-density recording/reproducing.

〔Effect of the invention〕

As described above, the magnetic recording/reproducing circuit according to the present invention can demodulate data with a small bit shift up to a high recording density when the reproduced waveform at a low density is an asymmetric rectangular waveform.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of an embodiment of the present invention, Fig. 2a
-d are waveform diagrams for explaining the operation of the circuit of FIG. 1, and FIG. 3 is a bit shift characteristic diagram of this embodiment. In the figure, 1 is a differential circuit, 2 is a delay circuit, 3 is an attenuator, and 4 is a zero-cross detection circuit.

Claims (1)

[Claims] 1. A differentiating circuit for differentiating a reproduction input signal from a reproduction magnetic head, a delay circuit for delaying the output voltage of this differentiating circuit, an attenuator for attenuating the output voltage of this delay circuit, and a differential circuit for differentiating the output voltage of the differentiating circuit and the 1. A magnetic recording and reproducing circuit comprising: a zero-cross detection circuit that detects a point in time when the difference between the output voltage of the attenuator and the output voltage becomes zero.