JPS5836401B2 - Digital magnetic recording and reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is used as an external auxiliary storage device for electronic computers and the like.

The present invention relates to a method for inspecting the quality of information recorded on a recording medium when information is written in a digital magnetic recording/reproducing device such as a magnetic tape device.

Generally, in digital magnetic recording and reproducing devices, information is
It is written via a magnetic head according to a predetermined writing method, and recorded as a magnetization reversal pattern on the recording medium.

In the case of reproducing recorded information, a reproducing head is passed over the magnetization reversal pattern of the recording medium, an analog signal is obtained via the reproducing head, the peak position of this analog signal is detected, and the peak position is detected based on this. The recorded information is demodulated.

That is, the presence or absence of a peak signal is detected using a peak signal corresponding to the peak position and a synchronization signal synchronized with the peak signal, and information is reproduced.

However, the peak signal generally includes low frequency errors called wow and flutter, and high frequency errors called jitter.

Of these, wow and flutter are low-frequency frequency fluctuations caused by the recording medium running system or vibration of the medium, while jitter is caused by noise generated in the medium or playback circuit system or by a peak shift phenomenon caused by magnetization reversal patterns. This is a high frequency frequency fluctuation.

For this reason, in conventional digital magnetic recording and reproducing devices, the oscillation of the synchronization signal oscillator is synchronized with the frequency fluctuations due to low frequency fluctuations due to wow and flutter, thereby preventing erroneous information due to these fluctuations. Trying to avoid detection.

However, since jitter is irregular frequency fluctuation, it is impossible to determine information without error using a synchronized synchronization signal, as in the case of low frequency fluctuation.

For example, if one of the consecutive peak signals
If the bit shifts in the delay direction and the synchronization signal tries to follow it, and the l bit of the next peak signal shifts in the advance direction, the phase shift will be greater than when the synchronization oscillator does not follow the peak signal. becomes larger, which has the opposite effect.

Therefore, it is not possible to track peak shift phenomena and noise that cause irregular frequency fluctuations, and since no remedies have been taken, the amount of peak shift (phase shift) exceeds a certain level. In this case, reading
It was impossible.

Therefore, it is necessary to reduce the phase shift due to the peak shift phenomenon at the time when information is written on the recording medium.

Conventionally, when writing information, the written information is read to check whether the information is correctly written on the recording medium. Even if I join,
In addition, in the case of normal reading, the detection of the phase shift error due to the peak shift phenomenon is performed as long as it does not cause misjudgment of information. To prevent errors from being detected, the allowable range for phase shift detection is widened.

Conventionally, by doing this, it has been possible to discriminate information without error.

However, changing the phase shift detection allowable width requires a very complicated circuit, and the device itself has disadvantages such as being large and expensive.

It is therefore an object of the present invention to eliminate the above-mentioned drawbacks,
For this purpose, a device that reads information recorded on a recording medium and converts it into an electrical signal, and a synchronous oscillator that generates a synchronization signal synchronized with the electrical signal from the device that converts it into an electrical signal. and an information discriminator that discriminates the electric signal based on a synchronization signal from the synchronous oscillator, wherein the synchronous oscillator is configured to perform playback during writing compared to playback during reading. This can be achieved by improving the response characteristics in the case of The present invention will be explained in detail below with reference to the drawings.

FIG. 1 is a block diagram of a conventional apparatus for accurately determining information based on phase shifts.

In the figure, 1 is a magnetic head, 2 is an amplifier, 3 is a peak detector, 4 is a synchronous oscillator, 5 is a phase shift detector, and 6 is an input of control signals such as informing whether it is writing or reading. 7 is an information discriminator, 8 is an output line for reproduction information, and 9 is a line for outputting a phase shift error signal.

The signal read by the magnetic head 1 is amplified by an amplifier 2, and then its magnetization reversal position (peak point of the input signal) is detected by a peak detector 3.

The peak signal output by the peak detector 3 is input to a synchronous oscillator 4, and the synchronous oscillator 4 generates a synchronous signal synchronized with the input signal.

The peak signal is input to the phase shift detector 5, which detects the phase shift with the synchronization signal, and outputs a phase shift error signal via the output line 9 by detecting a phase shift exceeding a preset phase tolerance. and output it.

Further, the synchronous signal of the synchronous oscillator 4 and the peak signal are input to an information discriminator 6, and the information discriminator 6 discriminates the information.

Furthermore, as mentioned above, the synchronous oscillator 4 is designed to follow and synchronize low frequency fluctuations such as wow and Fuji vine with respect to the peak signal, but due to the peculiarities of magnetic recording. In response to irregular frequency fluctuations at high frequencies, such as shifts in the peak point due to mutual sweating of information (peak shift) and jitters due to high-frequency noise, the system synchronizes and generates a stable synchronization signal so as not to follow. It has become.

Therefore, if the peak shift becomes larger than a certain level, erroneous determination of information may occur, so the phase shift detector 5
The phase shift between the peak signal and the synchronization signal is detected, and if this exceeds a set value, it is detected as an error.

However, it is important to avoid errors no matter what, so it is necessary to improve the quality of the information written on the magnetic recording medium, and when writing, strictly check for peak shifts. There is a need to.

That is, conventionally, in the case of reproduction during writing, peak shift checks have been made stricter by narrowing the allowable amount of the phase shift detector 5.

This improves the quality of information on the recording medium.

As a result, in the case of reproduction during reading, the permissible amount of the phase shift detector can be expanded compared to the case of writing, to the extent that erroneous discrimination of information does not occur, and as a result, throughput can be improved.

However, as described above, detecting the phase shift between the synchronization signal and the peak signal and changing the detection width of the phase shift with high accuracy requires a very complicated circuit and the device itself becomes large. The drawback was that it was very expensive.

Accordingly, the present invention provides a device as shown in FIG. 2 to eliminate these drawbacks.

The invention will now be described with reference to FIG.

In the figure, FIG. 2 shows a block diagram of a demodulation circuit.

Items with the same symbols as in Figure 1 indicate the same items.
0 indicates an input line for providing a control signal to the synchronous oscillator.

Information written on the recording medium is read by a magnetic head 1, amplified by a read amplifier 2, a peak point is detected by a peak detector 3, and a peak signal is sent out.

This peak signal is input to a synchronous oscillator 4, which generates a synchronous signal synchronized with the peak signal.

The synchronization signal and peak signal generated in this manner are input to the information discriminator 6 and compared, and reproduced information is outputted via the output line 8.

At this time, the phase shift detector 5 detects the phase shift between the peak signal and the synchronization signal, and determines whether or not the phase shift is greater than a tolerance value.

If this phase shift exceeds a permissible value, a phase error signal is generated.

Further, the response characteristics of the synchronous oscillator 4 are changed by the control signal 10.

Next, FIG. 2 shows a specific configuration diagram of a synchronous oscillator.

In the figure, 11 is the peak signal from the peak detector 3;
12 is a phase difference detector, 13 is a loop filter, 14 is an amplifier, 15 is a voltage controlled oscillator, 16 is an output line from which a synchronizing signal is sent from the synchronous oscillator, and 17 is a feedback line.

The phase detector 12 detects the phase difference between the output 17 of the voltage controlled oscillator and the input peak signal 12, and the phase difference output is inputted to the voltage controlled oscillator 15 via the loop filter 13 and the amplifier 14, and the voltage controlled oscillator By changing the oscillation frequency of the oscillator 15, the phase difference (therefore the frequency difference) between the output signal 12 and the peak signal 11 is controlled to be zero.

Considering the transfer function of this loop, we get It can be shown as

However, Ka is the gain of the amplifier 14, and Kd is the gain of the phase difference detector 12.
, Kv is the gain of the voltage controlled oscillator, and F(s) is the transfer function of the filter.

Now, if the phase of the input signal suddenly changes, the output signal of the voltage controlled oscillator 15 will not follow it immediately, but will have a specific response characteristic determined by the loop constants Ka, Kd, Kv, F(s). follow according to.

This response characteristic affects the above-mentioned phase shift.

Therefore, in this embodiment, the gain Kd of the phase difference detector, which influences the response characteristics of the loop, is changed by the control signal 10 between reading during writing and normal reading.

By doing this, when reading during writing, by improving the response characteristics, the synchronous oscillator can actively respond to the peak shift phenomenon, and as described above, the phase shift detector More phase shifts are detected and errors are more likely to occur.

In this way, when the peak shift phenomenon exceeds a certain phase difference, it is determined as an error and rewriting is performed as described above.

The information written in this way becomes high quality information with a very small amount of peak shift.

In addition, in the case of normal reading, the control signal 10 is used to deteriorate the response characteristic of the loop to a convenient degree in order to improve the throughput of information as long as information is not misjudged, contrary to the above. By controlling the gain of the phase difference detector 12, it becomes possible to discriminate information without error.

As described above, the present invention does not change the tolerance of the phase shift detector, but rather changes the response characteristics of the synchronous oscillator so that the peak shift phenomenon can be actively followed during reading during writing. By improving the response characteristics, phase shift errors are detected, and if there is a phase shift beyond a certain level, it is detected as an error and rewriting is performed to improve the quality of the written information.

In addition, during normal reading, the response of the synchronous oscillator is degraded to a convenient degree so that it does not follow the peak shift phenomenon, and as long as information is not misjudged, the reading throughput can be reduced by simply detecting the phase shift. The aim is to improve the

As described above, according to the present invention, the response characteristic of the synchronous oscillator is changed instead of changing the phase shift detection width of the phase shift detector as in the conventional case. This has the effect of making it possible to distinguish information without any confusion.

In the present invention, the gain of the phase difference detector is changed in order to change the response of the synchronous oscillator, but it is also possible to change the constants of the LF, amplifier, etc., or to combine them.

Furthermore, various check levels can be set by not only switching between two stages of reading during writing and normal reading, but also switching between multiple stages according to various other reading and writing states.

[Brief explanation of the drawing]

FIG. 1 is a general block diagram of a demodulation circuit of a conventional digital magnetic recording and reproducing apparatus, FIG. 2 is a block diagram of a demodulating circuit of a digital magnetic recording and reproducing apparatus of the present invention, and FIG.
1A and 1B each show a configuration diagram of a synchronous oscillator according to the present invention. In FIG. 2, 1 is a magnetic head, 2 is an amplifier, 3 is a peak detector, 4 is a synchronous oscillator, 5 is a phase shift detector,
6 is an input line for a control signal that indicates whether it is writing or reading, 7 is an information discriminator, 8 is an output line for reproduction information, 9 is a line for outputting a phase shift error signal, and 10 is a synchronous oscillator. 11 is a peak signal from a peak detector, 12 is a phase difference detector, 13 is an input line for giving a control signal to
14 is a loop filter, 14 is an amplifier, 15 is a voltage controlled oscillator, 16 is an output line from which a synchronous signal is sent from the synchronous oscillator, and 17 is a feedback line.

Claims (1)

[Claims] 1. A device that reads information recorded on a recording medium and converts it into an electrical signal, a synchronous oscillator that generates a synchronization signal synchronized with the electrical signal from the device that converts it into an electrical signal, and In a digital magnetic recording/reproducing device having an information discriminator that discriminates the electric signal based on a synchronization signal from a synchronous oscillator, the synchronous oscillator is configured to have a synchronous oscillator for reproduction during writing, as compared to reproduction during reading. A digital magnetic recording/reproducing device characterized by improved response characteristics.