JPH0346882B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording and reproducing apparatus, and more particularly to a magnetic recording and reproducing apparatus suitable for reproducing signals written on a magnetic disk.

In a conventional magnetic recording/reproducing device, a peak pulse that inverts in response to the peak point of an analog signal read out by a magnetic head is emitted for a predetermined period of time (this time is used for the next gate pulse described later). corresponding to the delayed peak pulse signal obtained by delaying the gate pulse by a certain amount (determined empirically within the time just before the gate pulse of Using an inverted gate pulse, the reproduction pulse is set to "1" when the gate pulse is "1" at the rising edge of the delayed peak pulse and when the gate pulse is "0" at the falling edge of the delayed peak pulse. By doing so, we were able to obtain playback data.

However, in recording media such as magnetic disks, the peak point of the analog signal read by the magnetic head may become blunt due to defects such as scratches, resulting in a predetermined deviation from the peak point of the analog signal. The time required for the signal to decrease in quality may be longer than in the case of a regular analog signal.

The longer the time required for the analog signal to decrease by a predetermined amount from the peak point, the slower the rise of the gate pulse signal becomes.

As a result, according to the conventional device, even if the gate pulse obtained from the normal analog signal becomes "1" at the rise of the delayed peak pulse, the gate pulse obtained from the blunted analog signal remains "0". Or, even if the gate pulse obtained by the regular analog signal becomes "0" at the falling edge of the delayed peak pulse, the gate pulse obtained by the blunted analog signal becomes "1".
In such a case, a reproduction pulse corresponding to the peak of the analog signal cannot be obtained, so there is a problem that correct reproduction data cannot necessarily be obtained.

In view of the problems in the conventional device described above, an object of the present invention is to respond to the rising edge of the gate pulse when the delayed peak pulse is "1" and the gate pulse rises with a delay in the rising edge of the delayed peak pulse. If the delayed peak pulse is “0” and the gate pulse falls behind the falling edge of the delayed peak pulse, a reproduced pulse is formed in response to the falling edge of the gate pulse. Based on this idea, the objective is to reduce the number of missing reproduction pulses in a magnetic recording/reproducing device and obtain relatively accurate reproduced data.

The present invention includes a magnetic head for reading signals written on a magnetic recording medium, a peak pulse generating means for detecting a peak point of a read signal read by the magnetic head, and a peak pulse generating means for detecting a peak point of a read signal read by the magnetic head. delayed peak pulse generating means for delaying the peak point detected by the readout signal for a predetermined time; gate pulse generating means for detecting the peak point of the read signal and detecting a decrease by a predetermined value from the peak point; After the means detects that the peak point has decreased by a predetermined value, the delayed peak pulse generating means generates a reproduction pulse in response to the generation of the delayed peak point, and the delayed peak pulse generating means generates a delayed peak pulse. A magnetic recording device comprising: reproduction pulse generation means for generating a reproduction pulse in response to the gate pulse generation means detecting that the gate pulse generation means has decreased by a predetermined value from the peak point after the peak point has been generated. A playback device is provided.

Embodiments of the present invention will be described based on FIGS. 1 and 2. FIG. 1 is a block circuit diagram of a magnetic recording/reproducing apparatus applied to the present invention, and FIG. 2 is a waveform diagram for explaining the operation of the apparatus of FIG. As shown in the figure, an analog signal read out by a magnetic head 1 from a recording medium such as a magnetic disk is amplified to a necessary level by an amplifier 2.
An analog signal is obtained. The peak point of the waveform in FIG. 2a corresponds to the data "1" written on the magnetic medium. In the part of FIG. 2a, the dotted line shows a waveform when normally read, and the solid line shows a waveform whose peak point is blunted due to a defect in the magnetic medium or the like. The analog signal shown in FIG. 2a is input to the peak pulse generation circuit 3. The peak pulse generating circuit 3 is composed of, for example, a differentiating circuit that differentiates an input signal and a zero crossing circuit that generates a peak pulse corresponding to the zero crossing point of the output of this differentiating circuit, and the obtained peak pulse is used as a second Figure b ₁
As shown in FIG. 2A, the waveform is inverted from "0" to "1" or from "1" to "0" corresponding to the peak point of the waveform in FIG. 2a. In this embodiment, the peak pulse generating circuit 3 also obtains the peak pulse shown in FIG. 2 b ₂ which is an inverted signal of the peak pulse shown in FIG. 2 b ₁ . The peak pulses b ₁ and b ₂ in Fig. 2 are appropriately delayed and the output of the peak pulse generation circuit 3 is as shown in Fig. 2.
Delayed peak pulses b′ ₁ and b′ ₂ are obtained. on the other hand,
The analog signal of FIG. 2a is also input to the gate pulse generation circuit 4. The gate pulse generation circuit 4 is composed of a drop detection circuit that generates a pulse that is inverted when the level decreases by a certain value or more from the peak point of the analog signal shown in FIG. 2a, for example. Gate pulses shown in Figure 2 c ₁ and c ₂ that are inverted to each other are obtained. The method for obtaining the delayed peak pulse and gate pulse described above is exactly the same as the conventional method.

In parts c ₁ and c ₂ of Figure 2, the rise of the gate pulse obtained from the blunted analog signal (solid line in the figure) is different from the rise of the gate pulse obtained from the regular analog signal (the dotted line waveform in the figure). The fact that they are late is noticed. In order to obtain a reproduction pulse from the obtained delayed peak pulse and gate pulse, the above two types of pulses are input to the reproduction pulse generation circuit 5 according to the present invention. The reproduction pulse generation circuit 5 generates a reproduction pulse in response to the delayed peak pulse generation means generating the delayed peak point after the gate pulse generation circuit 4 detects that the predetermined value has decreased from the peak point. At the same time, in response to the fact that the gate pulse generating circuit 4 detects that the peak point has decreased by a predetermined value after the delayed peak pulse is generated by the delayed peak point pulse generating means, the reproduction pulse of FIG. 2d is generated. has been made to occur.

That is, in the reproduction pulse generation circuit 5, when the gate pulse shown in Fig. 2 _c1 is in the "1" state at the rise of the delayed peak pulse shown in Fig. 2 b' ₁ , and when the delayed peak pulse shown in Fig. 2 b' ₂ When the gate pulse shown in Fig. 2 _c2 is in the "1" state at the rise of the peak pulse, the reproduction pulse shown in Fig. 2 d is generated as in the conventional case, and the delayed peak pulse shown in Fig. 2 b' ₁ is "1". If the gate pulse shown in Figure 2 c ₁ rises when the state is "1", and the gate pulse shown in Figure 2 C ₂ rises when the delayed peak pulse shown in Figure 2 b' ₂ is in the state "1". It has a flip-flop (for example, Motorola's MC10130) which is adapted to obtain the reproduction pulse shown in FIG.

As shown in part d of FIG. 2, according to the present invention, the reproduced pulse indicated by the dotted line, which is missing according to the conventional method, is replaced by the rising edge of the gate pulse corresponding to the blunted peak. (Fig. 2 c ₁
(part)) is obtained without any omissions with a slight delay. The obtained reproduction pulse has temporal fluctuations due to pattern effects characteristic of digital magnetic recording and other noises. For this reason, as in the conventional method, a wind pulse (e ₁ , e ₂ in Fig. 2) synchronized with the period of the reproduction pulse is formed by the PLL circuit in the phase-locked circuit 6, while the wind pulse in the phase-locked circuit 6 and demodulator 7 is The mono-multivibrator (delay circuit) is used to adjust the average position of the reproduction pulse so that it comes to the center position of the next wind pulse (Fig. 2 d').

According to the present invention, the regenerated pulse obtained corresponding to the blunted peak is obtained later than the rising edge of the delayed peak pulse. Therefore, in another aspect of the present invention, the average position of the regenerated pulse is the same as that of the wind pulse. (Fig. 2 d'').The maximum value of the degree of adjustment in this case is (wind pulse width) - (pattern effect,
It is possible to have a value of up to (temporal fluctuation due to noise, etc.)/2, but in reality a smaller value is selected. In this way, the reproduction pulse obtained in response to the blunted peak is compensated for being delayed from the rising edge of the delayed peak pulse, and by selecting the above adjustment range, other reproduction pulses are also maintained within the predetermined window. This guarantees the existence of this information in the data, thereby reducing the possibility of missing reproduction pulses and making it possible to obtain more accurate reproduction data.

In addition, such adjustment of the position of the reproduction pulse is as follows.
A mono multivibrator (delay circuit) provided in the phase-locked circuit 6 and demodulator 7 (provided before the phase-locked circuit 6 and demodulator 7)
This can be done by appropriately adjusting the delay time.

The demodulator 7 determines whether the reproduced pulse d' or d'' in FIG. 2 thus obtained is located in the section where the wind pulse e ₁ or e ₂ in FIG. The output of the demodulator 7 is "1" if the reproduced pulse exists in the "1" section of the wind pulse, and "0" otherwise (FIG. 2 f). can be obtained.

In the above description of the embodiment of the present invention, the peak pulse, delayed peak pulse, gate pulse, and window pulse are each formed by a pair of pulse trains having an inverted relationship with each other, but the present invention is not limited to this. Each pulse may be formed by a single pulse train.

According to the present invention, a reproduction pulse is formed in response to the delayed peak pulse generation means generating the delayed peak point after the gate pulse generation means detects that the delay peak point has decreased by a predetermined value from the peak point; A reproduction pulse is formed in response to the gate pulse generation means detecting that the delayed peak pulse has decreased by a predetermined value from the peak point after the delayed peak pulse is generated by the pulse generation means, thereby reducing the number of missing reproduction pulses. , relatively accurate playback data can be obtained.

Further, according to the present invention, it is possible to compensate for the fact that the regenerated pulse obtained in response to the blunted peak lags behind the rising edge of the delayed peak pulse, and to ensure that other regenerated pulses also exist within a predetermined window. As a result, the possibility of missing reproduction pulses can be further reduced, and more accurate reproduction data can be obtained.

[Brief explanation of drawings]

FIG. 1 is a block circuit diagram of a magnetic recording and reproducing apparatus applied to the present invention, and FIG. 2 is a waveform diagram for explaining the operation of FIG. analog signal,
b ₁ and b ₂ are peak pulses, b' ₁ and b' ₂ are delayed peak pulses, c ₁ and c ₂ are gate pulses, d is regeneration pulse,
e ₁ and e ₂ are wind pulses, d' and d'' are phase-adjusted reproduction pulses, and f is reproduction data. 1...Magnetic head, 2...Amplifier, 3...Peak pulse generation circuit, 4... ...Gate pulse generating circuit, 5... Reproducing pulse generating circuit, 6... Phase synchronization circuit, 7... Demodulator.

Claims (1)

[Scope of Claims] 1. A magnetic head for reading signals written on a magnetic recording medium, a peak pulse generating means for detecting a peak point of a read signal read by the magnetic head, and the peak pulse generating means for detecting a peak point of a read signal read by the magnetic head. delayed peak pulse generation means for delaying the detected peak point by a predetermined time in response; gate pulse generation means for detecting the peak point of the read signal and detecting that it has decreased by a predetermined value from the peak point; and the gate. After the pulse generating means detects that the predetermined value has decreased from the peak point, the delayed peak pulse generating means generates a reproduction pulse in response to the generation of the delayed peak point, and the delayed peak pulse generating means also generates a reproduction pulse. reproduction pulse generation means for generating a reproduction pulse in response to the gate pulse generation means detecting that the peak point has decreased by a predetermined value after the peak pulse has been generated; and reproduction pulse generation means generated by the reproduction pulse generation means. It is characterized by comprising: a phase synchronization circuit that generates a wind pulse synchronized with the pulse cycle; and a demodulator that demodulates the reproduced pulse by positioning the average position of the reproduced pulse ahead of the center position of the wind pulse. Magnetic recording and reproducing device.