JPS583117A - Magnetic recorder and reproducer - Google Patents

Abstract

PURPOSE:To decrease the peak shift without deteriorating the signal-to-noise ratio like timing correction at recording, by compensating the effect of a demagnetizing field produced at recording, in the stage of reproduction. CONSTITUTION:An input from an input terminal 61 is given to one input terminal 66 of a differential amplifier 64 via a delay circuit 62. The input signal is divided into a specified voltage dividing ratio at a voltage-divider 65 and given to another input terminal 67 of the differential amplifier 64. Waveforms 71-74 show waveforms which appear at the input terminal 66 of the amplifier 64 after a delay at the delay circuit 62. Waveforms 72-74 adding a waveform 75 to the waveforms 71-74 are outputted from the output of the differential amplifier 64. Through the operation stated above, the waveform having widened front edge as shown in the 71 subject to the demagnetizing field of the front bit of a magnetized medium is made thin, and the peak shift of the reproduced waveform shown in the overlapping can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording/reproducing device, and particularly to a reproducing circuit thereof.

As shown in FIG. 1, in a general recording and reproducing circuit of a magnetic recording and reproducing device, when write data is input to a written data input terminal 3, a predetermined code conversion is performed by a transformer 4, and the write data is input to the write circuit. 5 supplies a write current to the coil 6 of the magnetic head 1, and write data is recorded on the magnetic recording medium 2 as magnetization information. An example of the write current is shown at 21 in FIG.

During reproduction, magnetization information of the recording medium 2 is detected by the magnetic head 1, and a full signal voltage is induced in the coil 6. An example of this waveform is shown at 22 in FIG.

The read voltage 22 is amplified by the read amplifier 7, and the peak detector 9 detects a peak pulse corresponding to the peak timing of the read waveform. - An example is shown at 23 in FIG. At this time, the timing of the detected peak pulse is shifted from the recorded timing as shown at 24.25 in FIG. 2. This is due to interference between magnetization information recorded before and after. The peak pulse is supplied to a synchronous oscillator 11 and a demodulation circuit 13, and the synchronous oscillator 11 generates a clock signal synchronized with the average clock frequency of the peak pulse, and uses the clock to generate a data discrimination wind pulse. ) A demodulation circuit logically discriminates the read signal depending on whether or not there is a peak pulse within the discrimination window, and outputs it to the output terminal 14 as a read data pulse.

During this series of demodulation operations, the detected peak pulse may be detected with a relative shift from the recording timing due to interference of recorded magnetization information. This is generally called a peak shift, and if this peak shift becomes large, the signal may jump out of a predetermined discrimination window or may be mixed in excessively, causing data errors.

FIG. 3 shows an example of a recording current and an example of a corresponding peak shift. In general, a peak shift occurs when the magnetization reversal interval is asymmetric between the front and back, and the interference of the magnetization information becomes asymmetric.
Even if the magnetization reversal intervals before and after the central magnetization reversal portions of 3 are symmetrical, their peak shifts will have different values such as 37.38. This is because during recording, the demagnetizing field generated from the previous magnetization pattern that has already been recorded is superimposed on the recording, and the timing at which all recording is desired is also shifted before the recording. This shift increases as the demagnetizing field increases, so the section 3 where the magnetization reversal interval is small
3 is larger than the section 32 where the magnetization reversal interval is large. The peak shifts 39 and 40 are caused by the superposition of the effect due to the demagnetizing field and the effect due to the asymmetry of the magnetization reversal interval described above.

The conventional method for fully compensating for these peak shifts is to record by shifting the recording current reversal timing in advance in the opposite direction to the expected peak shift direction, as shown in Figure 4. . At the recording point 45, since the magnetization reversal interval before and after is asymmetrical, a peak shift occurs on the rear side, so the recording is performed with a shift forward by a time 47.

As a result, the magnetization reversals 48 and 49 are shorter than the normal magnetization reversal interval by time (46+47), and the magnetization interference increases, resulting in a reduction in the reproduced signal voltage and a deterioration of the signal-to-noise ratio.

The present invention provides a magnetic recording/reproducing device which compensates for the peak shift during recording due to the demagnetizing field of the previous recorded bit without deteriorating the overall signal-to-noise ratio, and improves the reliability of read data. It is.

The present invention provides a reproducing circuit for a magnetic recording/reproducing device including: a delay circuit that delays the entire reproduction signal from a magnetic head to generate a first signal; The present invention is characterized in that it is comprised of an attenuator that generates a second signal, and a subtraction circuit that generates a difference between the first signal and the second signal.

During recording, the demagnetizing field of the immediately previous magnetization pattern that has already been recorded is superimposed and recorded, so the recorded magnetization pattern is distorted. This distortion occurs when the recorded magnetization pattern sequence is separated into individual isolated magnetization reversal reproduction signals as a superposition of isolated magnetization reversal reproduction signals. Since the waveform becomes wide, the width of its leading edge is made small during reproduction to fully compensate for the effects of the demagnetizing field.

Next, embodiments of the present invention will be described with reference to all the drawings.

5- FIG. 5 shows an example of an isolated magnetization reversal reproduction waveform.

52-53 are waveforms that are approximately symmetrical to the center line 51 drawn from the peak of the waveform, and in fact, it is easy to make isolated magnetization reversal reproducing wave engraving almost symmetrical.

36 in FIG. 3 shows an example of the peak shift that occurs in the case of a recording current like 31, but when we calculate the isolated magnetization reversal reproduction waveform to cause all of this peak shift, we obtain the following: The leading edge becomes wider as shown in Fig. 54. As already explained, the warpage is caused by the superimposition of the demagnetizing field generated from the previous recorded bit during recording.

FIG. 6 shows an embodiment of the present invention. The circuit of the present invention replaces the readout amplifier 7 and peak detector 9 of the conventional circuit of FIG.
It is realistic to insert it between 61 is an input terminal of this circuit, and the input signal is passed through a delay circuit 62 to a differential amplifier 64.
The input signal is divided into a predetermined voltage division ratio by a voltage divider 65 and then passed through a differential amplifier 64.
is connected to the other input terminal 67Vc. A resistor 63 is a terminating resistor of the delay circuit 62. Differential amplifier 64-6
The difference between the signal voltages appearing at the input terminals 66 and 67 is amplified and output to the output terminal 68.

Figure 7 is a diagram explaining the operation of Figure 6, with waveform '11-7
4 is a waveform obtained by separating the reproduced waveform of the signal recorded under the influence of the demagnetizing field of the front pit of the magnetized medium into isolated waveforms, which are delayed by the delay circuit 62 and then sent to the differential amplifier 64. 2 shows the waveform appearing at one input terminal 66 of . 75 is a waveform obtained by dividing the input waveform by the voltage divider 65 and inverting the polarity of the waveform appearing at the other terminal 67 of the differential amplifier 64; Waveform 72-7 which is the sum of 71-74 and waveform 75
4 is output. By the above operation, the influence of the demagnetizing field of the front pit of the magnetized medium, the waveform with a widened leading edge as shown in 71, is reduced, and the peak shift of the reproduced waveform represented by the superposition of these waves is reduced.

In the above explanation, as mentioned above, the reproduced waveform is shown as a waveform separated into all isolated waveforms, and in reality, the waveforms 71-74 and 72-74 cannot be observed. The m force waveform of the circuit of FIG. 6, which has an isolated waveform that is approximately longitudinally symmetrical, is 73- in FIG. 7.
74, the width of the leading edge with respect to the center line is observed to be smaller. When a continuous pattern is recorded, the leading edge has the effect of spreading due to the demagnetizing field of the front pit, so the result is the same as a superposition of symmetrical waveforms.
It is possible to reduce the peak shift caused by the influence of the demagnetizing field.

As explained above, the present invention compensates for the effects of the demagnetizing field generated during recording during reproduction, and has the effect of completely eliminating the peak shift without completely deteriorating the signal-to-noise ratio, unlike timing correction during recording.

[Brief explanation of drawings]

Figure 1 is a diagram showing an example of a magnetic recording/reproducing circuit, Figure 2 is a diagram showing waveforms of each part to explain the entire operation of Figure 1, and Figure 3 is a recording current waveform and its corresponding waveform. Figure 4 is a diagram showing a recording current waveform to explain a conventional circuit that compensates for peak shift error, and Figure 5 is a diagram showing an example of the magnitude of peak shift caused by FIG. 6 is a diagram showing an embodiment of the present invention, and FIG. 7 is a diagram showing waveforms for explaining the present embodiment. 1... Magnetic head, 2... Recording medium,
3...Write data input terminal, 4...
Modulator, 5...Writing circuit, 6...Magnetic head coil, 7...Reading amplifier, 9...
... Peak detector, 10 ... Peak detector output line, 11 ... Synchronous oscillator, 12 ...
...Data discrimination window output line, 13...Demodulation circuit, 14...Read data output terminal, 21,
31゜41.42...Write current waveform, 22.
... Readout waveform, 23 ... Peak detection pulse, 26 ... Discrimination wind pulse, 27 ...
-... Read data pulse, 36... Graph showing peak shift amount, 61... Input terminal of embodiment of the invention, 62... Delay circuit, 63...・・・
... Termination resistor, 64... Differential amplifier, 65.
...Voltage divider, 66.67...Differential amplifier input terminal, 68...Output terminal of the embodiment of the invention Z or

Claims (1)

[Claims] a delay circuit that generates a first signal by delaying the reproduction signal from the magnetic head with a full-valve press meter; the reproduction signal amplitude f;
A regeneration circuit comprising an attenuator that generates a second signal whose amplitude is small compared to the original signal amplitude, and a subtraction circuit that generates the entire amplitude difference between the first and second signals. A magnetic recording and reproducing device having.